The Effects Of Added Transportation Capacity
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Travel Model Improvement Program
The Department of Transportation, in cooperation with the
Environmental Protection Agency and the Department of Energy, has
embarked on a research program to respond to the requirements of
the Clean Air Act Amendments of 1990 and the Intermodal Surface
Transportation Efficiency Act of 1991. This program addresses the
linkage of transportation to air quality, energy, economic growth,
land use and the overall quality of life. The program addresses
both analytic tools and the integration of these tools into the
planning process to better support decision makers. The program
has the following objectives:
1. To increase the ability of existing travel forecasting
procedures to respond to emerging issues including;
environmental concerns, growth management, and lifestyle along
with traditional transportation issues,
2. To redesign the travel forecasting process to reflect changes
in behavior, to respond to greater information needs placed on
the forecasting process and to take advantage of changes in
data collection technology, and
3. To integrate the forecasting techniques into the decision
making process, providing better understanding of the effects
of transportation improvements and allowing decision makers in
state governments, local governments, transit operators,
metropolitan planning organizations and environmental agencies
the capability of making improved transportation decisions.
This program was funded through the Travel Model Improvement
Program.
Further information about the Travel Model Improvement Program
may be obtained by writing to:
Planning Support Branch (HEP-22)
Federal Highway Administration
U.S. Department of Transportation
400 Seventh Street, SW
Washington, D.C. 20590
The Effects of Added
Transportation
Capacity
Conference Proceedings
December 16 and 17, 1991
Prepared by
Gordon A. Shunk
Texas Transportation Institute
1600 East Lamar Boulevard, Suite 120
Arlington, Texas
Funded by
U.S. Department of Transportation
Federal Highway Administration
Federal Transit Administration
Office of the Secretary
U. S. Environmental Protection Agency
Distributed in Cooperation with
Technology Sharing Program
Research and Special Programs
Administration
U.S. Department of Transportation
Washington, D.C. 20590
DOT-T-94-12
Contents
Day One: Describing the Problem . . . . . . . . . . . . . . . . . 1
Transportation Investment and Metropolitan Economic Development:
A Reconnaissance of Research Availability and Requirements
Alan E. Pisarski. . . . . . . . . . . . . . . . . . . . . . . . . 3
Effects of Added Transportation Capacity on System Performance
Richard H. Pratt. . . . . . . . . . . . . . . . . . . . . . . . . 7
The Effects of Added Transportation Capacity on Travel
Ryuichi Kitamura. . . . . . . . . . . . . . . . . . . . . . . . .11
Effects of Added Transportation Capacity on Development
Michael V. Dyett. . . . . . . . . . . . . . . . . . . . . . . . .17
Other Effects: Institutional and Financial Context
Sheldon M. Edner. . . . . . . . . . . . . . . . . . . . . . . . .23
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Day Two: How to Address the Problem . . . . . . . . . . . . . . .31
Environmental Effects of Added Transportation Capacity
John H. Suhrbier. . . . . . . . . . . . . . . . . . . . . . . . .33
Forecasting Models
Daniel Brand. . . . . . . . . . . . . . . . . . . . . . . . . . .41
Experimental Design
Peter Stopher . . . . . . . . . . . . . . . . . . . . . . . . . .47
Closing Discussion. . . . . . . . . . . . . . . . . . . . . . . .55
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Appendix -- Conference Papers
57
The Travel Effects of Added Transportation Capacity
Gordon Shunk 59
Transportation Investment and Metropolitan
Economic Development: A Reconnaissance of
Research Availability and Requirements
Alan E. Pisarski 63
The Effects of Added Transportation
Capacity on Travel: A Review of Theoretical
Ryuichi Kitamura 79
Effects of Added Transportation Capacity on Development
Michael V. Dyett 97
Institutional, Financial, and Social Impacts of Induced
Transportation: Speculations on the Need for Research
Sheldon M. Edner 101
Environmental Effects of Added Transportation Capacity
John H. Suhrbier 103
Use of Travel Forecasting Models to Evaluate the Travel
and Environmental Effects of Added Transportation Capacity
Daniel Brand 105
Travel and Locational Impacts
of Added Transportation Capacity: Experimental Designs
Peter Stopher 113
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Day One: Describing the Problem
David, Chief of the Programming Branch of the San Francisco
Office of the Environmental Protection Agency, opened the
conference. He noted that one of the EPA's main interests in
participating in a conference that dealt with the impacts of added
transportation capacity was that frequently the regional offices
want to consider the potential growth inducing impact of proposed
highway projects. Federal and state agencies often disagree on
whether or not increased capacity leads to less congestion and less
air pollution. This disagreement, Calkins stated, has been going
on for over 10 years; but there was little in the way of unbiased,
extensive research to substantiate either claim. For this reason,
the EPA is interested in pursuing a multi-agency, multi-year study
that will address this issue.
Calkins outlined several benefits that should evolve from this
discussion. Overall, developing information that can be used to
improve the p g and decision-making process in air quality and
transportation projects will reduce conflicts. By being more
knowledgeable about the actual effect of added capacity,
transportation and air quality plans can be coordinated more
effectively. Modeling procedures can also be improved as more and
better information on travel behavior is developed. The conference
will assist in developing the state implementation plan control
strategies of the 1990 Clean Air Act Amendments (CAAA), as well as
support measures of the Intermodal Surface Transportation
Efficiency Act (ISTEA). Other benefits include more cost-effective
air quality improvement strategies and better justifications and
alternatives to the public for transportation control measures.
There should also be a focus on access, not just on mobility and
ease of travel issues. Access issues include providing
transportation facilities for the elderly, the poor, the young, and
the handicapped.
Calkins stressed the importance of study design and the need
to include all interested parties at the outset of the study,
including Metropolitan Planning Organizations (MPOs), federal
agencies, local air quality agencies, environmental groups, and
land use planners and developers. A long-term funding commitment
from all of these organizations will be necessary for a successful
study.
In conclusion, Calkins stated that the conference was an
opportunity to improve the quality of life, as health is the basis
for the CAAA and air quality regulations. By learning about how
travel growth patterns interact with existing infrastructure and
other factors, transportation and land use systems can be designed
that are efficient, clean, and provide good access to services,
jobs, and recreation.
Kevin Heanue, Director, Office of Planning of the Federal
Highway Administration, felt that the conference was a step in
seeking a broader audience in laying out a research agenda on the
issue of the impacts of added transportation capacity. By
identifying major and minor topics to address, better guidance can
be provided to those MPOs that are involved in air quality analysis
and state implementation plan updates.
Heanue stressed the importance of eliminating the use of
environmental specialists only at a project's end. By bringing
environmental resources into the project at the outset and
integrating those efforts with the planning efforts, the
relationships between air quality, travel, and development will be
better understood. As an example of an effort to promote this
integration, Heanue said, the FHWA merged the offices of
Environment and Planning in to one unit several years ago. The
FHWA also has a policy to foster strong linkages with the
environmental community. This is reinforced in the CAAA and ISTEA
legislation.
The responsibilities of the are changing, Heanue said. There
is a broader analytical framework within which there are more
choices than the traditional highway option; there are
highway transit options, for example. The MPOs are in a position
to make the initial recommendation whether transportation
investments are highway or transit.
Heanue said that a need exists for increased environmental
research and more accuracy and sensitivity in the present models.
By asking the questions of whether or not latent demand or induced
traffic is a valid concept, and how new capacity affects new travel
behavior, there will be new feedback for the modeling process. He
then stated the need for simpler modeling mechanisms, as opposed to
the modeling processes of the early 1960's. What is needed are
logical and practical models that recognize the accuracy of the
base data and target objective. Heanue then concluded his remarks
by suggesting that there were two agendas to approach at the
conference. One was the research agenda, where to invest the
research money for the best results, and the other was the
practice. What can be learned from the study that would benefit
the 280 MPO transportation planners who would be faced with the
implementation and technical responsibilities of the CAAA and ISTEA?
Edward Weiner, Senior Policy Analyst with the Office of the
Secretary of Transportation, served as moderator for the first
session and offered a conclusion to the introductory remarks. He
noted that it was encouraging to see the cooperation between the
EPA and the Transportation Department in the effort to implement
the various provisions of the CAAA. He also reiterated the general
questions that the conference would be trying to address. First,
what is known about the relationship between the various phenomena
involved and the effect of added capacity and induced travel?
Second, what are the key variables involved? And, third, can a good
understanding of how to measure the process be gained in order to
design impact or measurement studies that will successfully measure
this phenomena?
2
Transportation Investment and Metropolitan Economic Development:
A Reconnaissance of Research Availability and Requirements
Alan E. Pisarski
This presentation outlined available research and literature
for a research effort on land use impacts of major rail and related
investments. The presentation consisted of three main topics: a
review of the findings of a research and literature review, a
discussion of ways to expand on the review, and questions that will
be beneficial to the intent of the conference.
One of the major findings of the literature review is that the
subject of land use impacts is debatable, as there is no common
terminology throughout the literature. Material is available in
all aspects of transportation research including land use
development, economic development, impact analysis, and efficiency
studies. The material also extends into other disciplines such as
economics, geography, and sociology. Several consistent elements
are evident, in spite of the disparity of sources. There is a
tendency to focus on the economic effects of investment, most
noticeably the employment and construction effects. The economic
effects are further divided into direct, indirect, primary, and
secondary influences. The older literature focuses more on the
traditional logistical models of the coal or steel industries and
their relation to transportation, while the newer materials looks
at the new economic effects of the service industry. The ability
to include the transportation element in the new service-oriented
economy is not well developed. Finally, for the most part, the
literature centers around major transportation projects, such as
San Francisco's Bay Area Rapid Transit (BART) project The emphasis
and analysis on these large undertakings has been on generational
effects, demand changes, and land use effects. Several problems
are evident with the before-and-after impact studies generated from
the large projects. Often, these studies were under-funded and never
completed; or after long periods of time, the findings are irrelevant,
given the changes that occurred.
Over the years, highway analysis shifted from attempts to
justify the facility in terms of its development effects to a more
conciliatory tone of how to solve development-generated problems,
such as congestion and environmental impacts. There currently is a
shift back to the economic development argument as more projects
such as toll roads are being considered by private developers or
public/private cooperatives.
The aviation sector can be studied as an example of economic
development. The aviation industry, airports, and air travel
capability are a considerable economic engine in any region. Few
of the studies reviewed for the presentation focus on the changes
in the total economic capability and comparative advantage of a
region as a result of changes in local transportation. Aviation
can be one of the dramatic economic drivers in a community. This
is an area in which to study changes in investments and services
and the impacts they have on regional economic climates and
developments.
One question that arises from the available research is, is it
possible to get beyond a basic assumption that transportation is a
necessary, but inconsistent, condition of growth? Additional
questions generate from this; for
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example, why is there growth adjacent to some transit stations, but
not others? What are the positive and negative effects of density?
Why are some areas revived by transit development and others are
not?
The question of latent demand for local travel is an important
element of added capacity impact studies and should be the center-
piece of new research topics. How much of travel demand is latent?
How do various groups manifest this demand? The tourism industry
assumes that there is an enormous quantity of latent demand, and
they provide the means and opportunity for demand satisfaction.
There is little research available on latent demand; however, the
National Personal Transportation Study (NPTS) data being examined
for the Federal Highway Administration are a possible source for
further study material.
There has been an 18 percent increase in passenger miles
traveled from 1983 to 1990. The increase is equally divided
between increases in population, average trip length, and per
capita trip increases. Is the increase in trip rates and the
increase in trips per capita a manifestation of latent demand? If
the average trip length increased from 8 to 9 miles, are people
better or worse off; and what is gained by the extra mile, greater
choice, greater opportunity, lower housing costs, better jobs, or
wasted effort? Almost every urban trip culminated in an economic
transaction or something of social value, and the shift from latent
to actual travel demand should be suppressed.
The increase in travel demand is partially the result of
social changes. Also, uses of alternatives to the single occupant
automobile has declined, automobile occupancies were down and
transit use, walk to work, and telecommuting have all declined.
Average travel times have also decreased. The social changes that
have had an impact on travel demand are an increase in the vehicle
miles traveled by females which has risen 50 percent since 1983 and
an increase in single occupancy vehicle use for trips to work by
the poor, as examined by the American Housing Survey. All of these
changes are part of the democratization of travel which is being
encouraged by the low cost of transportation in America.
In conclusion, Mr. Pisarski commented on the feasibility of
travel pricing. There is concern that there will be adverse
effects on lower income populations if pricing mechanisms are
initiated. It will be critical to consider who will be priced out
of the transportation system by such measures and the effect this
will have on people's lives. These considerations should become a
serious part of the research evolving from the conference.
Open Discussion
The discussion opened with a request for Mr. Pisarski to
comment on the decrease, rather increase, of average trip length
that was occurring in several parts of the country. This decrease
is the result of many jobs shifting to the suburbs in contrast to a
population shift to the suburbs in search of lower housing costs.
In some communities, these two shifts have balanced out the average
trip length. One interesting aspect of the NPTS data was that
trips of over 30 miles to work have doubled as a percentage of all
trips.
The question was asked if work at home, or telecommuting, had
declined. Work at home statistics included both metropolitan
(professional employment) activities as well as traditional (rural
and agricultural) activities. The decline in farming and rural
activities accounted for this overall decline.
One participant noted that there were two possible research
objectives arising from the presentation: the social objective with
transportation demand elements and the economic focus at the state
and federal level. The question of how to bring both objectives
together was posed. The response was that while it was difficult
to coordinate both, it was important to realize how the economic
development issues manifest themselves in society. Both economic
and social issues can be addressed, for example, in a discussion of
possible solutions to the air
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pollution problem to get a better sense of the tradeoffs involved.
The suppression of travel demand was all too often considered to be
a positive action, regardless of the social or economic impact
involved. Increased awareness of the social and economic values
that are placed on travel by people is necessary.
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6
Effects of Added Transportation Capacity on System Performance
Richard H. Pratt
This presentation was an overview of the effects of added
transportation capacity on system performance. These effects are
based on several assumptions. First, the added capacity in
question is viable if there is sufficient demand for the added
facility or service, if the facility or service is sufficiently
attractive, and if the facility or service will be used. Second,
the added capacity is assumed to be definitely significant such as
a new arterial, freeway lane, high occupancy vehicle (HOV) lane
addition, or heavy rail transit project.
Eight different ways in which capacity can be achieved are
identified:
(1) Strategic highway infrastructure (toll free, mixed traffic)
(2) General mixed traffic highway capacity (toll free)
(3) Ramp metering, other TSM, IVHS
(4) Toll facility capacity
(5) HOV capacity
(6) Transit capacity (on separate ways)
(7) Transit capacity (in mixed traffic)
(8) Multimodal/manageable transportation infrastructure
(1) Strategic highway infrastructure development could be
differentiated from generalized highway expansion in that it
attempts to provide a missing link in an existing system and,
thereby, creates good capacity. By filling in missing links and by
removing bottleneck capacity restraints, better system use can
occur. Transit operations would also improve because the network
on which it operates would be more complete.
(2) The examples given for the generalized addition of mixed
traffic capacity included a new highway that parallels an existing
highway, a conventional freeway widening project, arterial to
freeway conversions, and freeway interchange improvements. Traffic
diverted to a new facility improves traffic flow until the system
is again overloaded. Improvements to conventional facilities
improve, and ultimately, traffic flow is increased. Parallel
facilities can provide traffic relief until they, too, become
congested. Traffic flow on facilities that provide access to
improved major facilities may also increase and become congested as
drivers choose to use the major facilities. An HOV lane that
exists on a facility where mixed traffic capability is added might
experience reduced use because the improved mixed traffic flow
reduces the incentive to use the HOV lane. Transit operations on
the new facility, however, would be improved, provided these
operations were expressed options. Roadway improvements that
effect increased traffic by single occupant vehicles have
detrimental effects on transit use. Those reductions initiate a
downward spiral as transit service is reduced to maintain
acceptable operating ratios.
(3) Capacity that is added by actions such as ramp metering
or Intelligent Vehicle Highway Systems (IVHS) will also have
significant impacts. Ramp metering results in the same effects as
generalized highway capacity additions; although it could be
managed, for example, by allowing HOV vehicles to bypass the
congestion. By backing up traffic, ramp metering often increases
the amount of traffic on intersecting streets and neighborhoods and
is also problematic at interchanges. In regard to the potential of
IVHS, there is concern that if a system were implemented that could
carry three times the present capacity of the conventional highway,
what effect would this increase have on the end points of the
system? This should be explored further in the IVHS program.
(4) There are several general highway
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capacity additions that have toll capabilities. A new toll highway
paralleling an existing highway, toll road widening, toll bridges
or tunnels, and new toll interchanges are examples. There are
several effects to consider as a result of these potential
additions, assuming that there is no longer a financial burden and
bond holders. Highway traffic flow on the toll facility win be
improved and controlled with the toll mechanism, and flow on
connecting and intersecting facilities might also be improved.
Highway traffic flow on parallel facilities will also improve.
Depending on the toll, the opportunity will arise to enhance the
HOV facilities, perhaps, by providing free HOV access. The toll
road can also potentially become an HOV facility, by letting the
HOV riders share in the cost. Free HOV access will also enhance
any connecting facilities. Transit operations, too, can be
enhanced by toll usage, much like freeways. Transit use at
parallel and intersecting facilities will be impacted depending on
the toll amount and system design.
(5) Possible examples of added HOV capacity include new HOV
facilities, added HOV lanes, HOV contraflow lanes where traffic is
imbalanced enough to truly add capacity, and HOV ramps and
interchanges. Traffic flow is presumed to improve on the facility,
except in cases of friction between HOV and low occupancy vehicles
(LOV) on diamond lane situations with crossing traffic flows. The
opportunity exists in this situation to manage the traffic flow
with changes in HOV occupancy requirements, however. Highway
traffic flow on connecting or intersecting facilities will either
increase or be mitigated. The opportunity also exists to manage
access volume with HOV ramps and interchanges, including mixed
traffic access at one location and HOV-only access at another.
Traffic flow on parallel facilities will be enhanced by additional
HOV capacity, and HOV operation will be enhanced and made more
manageable. HOV operations on connecting facilities will also be
enhanced. Express transit service will be enhanced, although the
impact on service often depends on facility design elements. HOV
facility design can have an impact on system performance. One HOV
facility in Los Angeles allows the bus to pull directly into the
station, then exit with ease, whereas a facility in Houston is
designed where the bus has to completely exit the HOV facility,
spend approximately five minutes at the station, then reenter the
HOV facility. Similarly, a situation exists on interstate 394, in
Minneapolis, where the buses, when utilizing the diamond lanes,
have to weave across traffic for the station exit with the rest of
the traffic, then repeat the competitive process to reenter the
facility.
(6) Examples of added transit capacity on separate guide ways
include new rail rapid transit and new bus rapid transit, either on
busways or on HOV lanes and facilities. Highway traffic flow on
parallel facilities has been improved near central business
districts (CBDs) and where surface transit volumes are large.
Traffic flow is also increased around and approaching transit
stations and terminals. An HOV operation parallel to a separate
transit way facility often induces a minor reduction in usage.
Transit service and capacity is enhanced, unless there are parallel
transit operations available. If transit operations intersect,
usage will be enhanced and a major opportunity exists for
restructuring to improve circumferential and local service.
(7) Mobility is a key element, as the previous capacity
categories and impacts were oriented to those with access to an
automobile. By providing transit capacity, mobility is enhanced
for that segment of the population without automobile access.
(8) Multimodal transportation infrastructure calls for the
provision of multiple modal options and the full integration of
those options. Manageable infrastructure will go beyond strategic
infrastructure in that it will be designed for maximum efficiency
in operation and use through complimenting and enhancing travel
demand management. Examples of this of capacity include HOV and
transit capacity on separate or concurrent ways within
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a corridor and added freeway capacity with HOV and buses. Another
example is added transportation capacity introduced in conjunction
with transportation system management and travel demand management
There are many expectations of multimodal/manageable
transportation capacity. Traffic flow on the facility can be
improved and managed as demand increases. There will also be
increased traffic flow on connecting or intersecting facilities,
but this could be addressed in the facility design. Traffic relief
will be seen on parallel facilities, and HOV and transit operations
will be improved as a result of the HOV and transit components of
the multimodal approach. Mobility will be improved for all sectors.
Open Discussion
One participant suggested that the use of toll facilities
implied an obligation to engage in planning and regulatory
mechanisms in order for the facility to function properly. The
toll mechanism could be one method to control the unused demand and
optimize the facility. The question was raised whether public
policy issues were being considered with an increased role for
tolls and other transportation pricing mechanisms. Mr. Pratt
replied that while toll facilities can provide advantages, his
intent was to encourage discussion of tolls and their manipulation
as an element of transportation management objectives.
There was a brief discussion on what was described as the
poly-nucleation of American metropolitan areas. Historically, long
distance trips have increased as a result of urban expansion, while
the opportunities for short distance trips has decreased. The lack
of choice for people to conduct short distance trips by walking or
cycling or by making a short bus trip, and a subsequent loss of
economic opportunities available to people to meet daily needs
through shorter trips, leads to increased automobile dependency.
The complexity of the transportation system and the lack of modal
diversity leaves people with no freedom to choose how to travel.
However, considering the poly-nucleation of cities, a phenomena
being experienced in Europe and Japan, as well in the United
States, a large city will be comprised of a constellation of small
cities. Within this framework the balance can be shifted back to
shorter trips within multiple centers, rather than longer trip
lengths focusing on a mono-center. The question was asked how the
polynucleation concept would mesh with multimodal/manageable
transportation capacity in regards to different travel modes
accommodating different travel lengths. Mr. Pratt replied by
describing a model of a modem multimodal activity center which
incorporates HOV system connections and land use designs for
pedestrian and bicycle access. This model is very idealized and
little has been done to actually implement the concepts; and it was
suggested that it be considered as another area for research.
The next question posed was how to determine the extent of the
effects of added capacity. Should the extent be measured
geographically for an entire urban area or be limited, for example,
to a 5-mile corridor; and should the effect be measured over time,
as well? One suggestion was made that if added capacity were
provided in smaller increments rather in large projects, some of
the negative effects could be alleviated. The comment was made
that one issue that had never been resolved was whether all vehicle
miles traveled (VMT) were equal or whether all personal miles
traveled (PMT) were equal, regardless of trip length. As an
example, one participant asked if a 30-mile trip, in terms of its
demands on public investment, was more potent a 1-mile trip. It
was also suggested that frequently the geographical extent to which
transportation effects were studied needed to be increased. A sup-
porting example was offered of an alternative penetrator highway
proposal in the Washington, D.C., area. The forecast was to build
the highway only far enough into the D.C. area to serve some of the
suburban areas but not all the
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way into the area. By extending the affected area analysis,
however, it was shown that the facility would be attractive for
people who, in fact, did want to drive all the way in, adversely
effecting neighborhoods and arterials. The discussion dosed with a
suggestion that the spatial question in determining the affected
area to analyze, as well as the element involved in the effects of
added transportation capacity, would be ideal research topics.
10
The Effects of Added Transportation Capacity on Travel
Ryuichi Kitamura
This presentation attempts to address the question of induced
travel and other effects of added transportation capacity. It
considers theoretical approaches as well as empirical evidence.
The presentation is divided into three parts starting with a brief
description of the economic definition of travel supply and demand,
followed by a discussion of the paradigm of constant travel
budgets, and concluding with the problem of multiple linearity re-
gression.
According to economists, travel demand relates to travel
costs. For example, if the cost of time spent traveling to a
desired location is too great, fewer people will travel. As travel
costs decline, more people will be on the road. On the supply
side, travel costs will rise as more people use a facility. Added
capacity will result in more use and rising travel costs.
Travel behavior can be considered as resource allocation
behavior. Travelers allocate a certain amount of time for travel,
and an assumption can be made that when the travel time doubles,
for example, the number of trips also doubles. When the cost of
travel is reduced by added capacity, more people make more trips.
This is the message from the theoretical and economic analysis of
added capacity, although it has never been verified.
A theoretical approach to travel demand research presents the
concept of the constant travel time budget. A fixed amount of time
exists that travelers would like to spend traveling. One counter-
argument states that when capacity is improved and when travel
costs decline, people will use the time saved to make even more
trips. This paradigm generates counter-intuitive results, however.
For example, reducing transit fare creates more automobile travel,
because the money saved on transit tickets is used for additional
automobile travel. This is one of the paradoxes that is derived
from the constant travel budget paradigm, and it is one of the
issues that should be researched. The constant travel budget,
however, is one of the few behavioral paradigms to be developed
into an operational model system.
One of the problems with studying the effects of added
capacity is the ecological correlation. In the environment in
which transportation planners work, everything is correlated with
everything else. Within the urban structure there is an activity
center or centers; and population densities and land prices tend to
decline further away from the center. Houses may be larger and
transit service may start to decline at some point away from this
center. All these variables are related (income is related to
residential choices, and urban density is related to car ownership
and household size) and create a highly complex environment in
which to plan because all the variables in the system are highly
multi-collinear.
It is possible to initiate the modeling process with only one
or two variables, but by adding variables so that the model will be
more useful and policy sensitive, it may start to fall apart. It
can be argued, then, that the solution is either to keep the model
simple or to remove all the multi-collinear variables and select a
set of relatively independent variables. Either solution has
problems and is not very well supported, theoretically.
By definition, induced traffic is related to trip generation,
diverted traffic is related to network assignment, transferred
traffic is related to mode choice, and shifted traffic is related
to trip distribution. Focusing on induced traffic raises several
questions. What is the impact of vehicle miles traveled (VMT) on
in-
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duced traffic? What is the impact of new or added facilities or
capacity on induced traffic?
Based on data from 23 cities there is strong evidence that
more facilities contribute to longer trip distance, but there is a
relationship between trip length and population. The average
speed, or network speed, should be lower with more capacity. There
is, however, a clear indication that as the average speed rises,
trip distances also rise. One problem is that freeway expansion
often takes place in areas of urban expansion where the population
is increasing. It is difficult to separate the pure facility
effect from the growth effect.
One previous study of induced travel added accessibility
majors to the trip generation equation, both attractions and
productions. The accessibility majors were found to be
significantly in school trip production and school trip attraction
models. This should not be the case because school trips are
similar to work trips and, therefore, should be insensitive to
accessibility factors. The same accessibility major was used in a
corridor analysis context to establish cause and effect linkages in
this multi-collinear environment. The link between accessibility
and trip generation had to be removed, however, in order to devise
a structure where accessibility influences automobile ownership,
which in turn influences trip generation. The results of these
studies suggest that there are no linkages between trip generation
and added capacity and that there is no induced traffic due to the
addition of capacity.
What is important, however, is the growth development and
growth effect that a new facility might have. There are several
things to consider and study in this assumption. First, it is
necessary to have a better understanding of trip timing. One
effect of congestion on trip g is, for example, that meetings are
scheduled to begin at 10:00 a.m. and end before 3-30 p.m in order
for participants to avoid peak travel times. For work trips,
people either leave earlier or stay later. If more travel options
were available, the response to the work trip would be different.
A better understanding of trip chaining is needed, as well. Trip
timing and trip chaining are closely related; for example, a person
might choose to run an errand during lunch rather than on the way
home because of congestion.
Even considering the difficulties in responding to a multi-
collinear environment, the complex models now being used can be im-
proved. Erroneous estimates may be produced because the tendency
is to produce attractive models with statistics and the right kinds
of signals. In an effort to produce these attractive models,
variables which may be counterproductive in the long run are often
removed. It may be necessary to consider a more complex system of
equations in a consistent and statistically desirable manner.
A wealth of data is available from origin destination studies
conducted in most metropolitan areas. The quality may not be
consistent, but it should be possible to select ten metropolitan
areas of different sizes with good data. By applying resources to
the data sets, cleaning them up, and supplementing those with
missing trip information, for example, the data sets should be
comparable to each other in a uniform manner. This process could
then be expanded to include land use data and network data. This
would be a expensive project, but the results would be a tremendous
information source for research. This resource base would make it
possible to compare trip timing in cities of different sizes,
different densities, and different congestion levels.
There is a limit to the theoretical approaches to studying the
effects of added capacity and a lack of consistent observations to
support any measurements of the impacts. One solution, the use of
the longitudinal panel, provides information on changes in income,
behavior, and facility use. This approach would be a beneficial
supplement to the traditional four-step model which is not based on
change. Combining these two approaches might offer a better set of
observations to analyze the effects of added capacity.
12
Open Discussion
The first question was in reference to the four-step model and
the suggestion that improvements to it are needed. Is the
planners' understanding of the induced traffic phenomena and added
capacity sufficient at this time to warrant adjusts to the four-
step model? Or, are additional measurements needed to see if the
four-step model is even applicable at this time? Growth and the
effects of development are the first order effects, not the induced
trip effect; and the four-step process deals only with the induced
effects. To include the additional effects will require a five- or
six-step model system.
One participant asked how much information was available
regarding off-peak trips. In some areas the off-peak travel
figures have increased more than anticipated. One participant
replied that little information is available on these trips. It
was suggested that the increase, in part, may be the result of the
increase in the female labor force.
The question was then asked if additional variables, from a
behavioral perspective, should be collected. Examples would be the
impact that the fear of crime has on transit ridership or the
effects of earthquakes on travel behavior. Also, is experiential
data beneficial in studying the effects of added capacity? Related
to these issues is the time frame and geographical context of the
impacts of new facilities. Combined, these elements create the
dynamic situation that may be impossible to cover in a traditional,
large-scale survey.
Participants discussed the definition of "induced" and its
various interpretations. One participant commented that separating
a highway's long-term land use impacts from the short term is
difficult. Another interpretation of induced traffic is that which
is encouraged by added capacity. If a new freeway is built and
travel times are improved, people will travel more often. The
additional trips are the induced travel.
A request was made to consider the growth stratification that
a community might experience. Development traffic will be
encouraged by land use changes, but these changes should be
separated into those that will occur regardless and changes that
are due to the added capacity. Natural growth, it was pointed out,
does not consider changes in land use.
The discussion then returned to the applicability of the four-
step model to the issues of added capacity. One participant
suggested that incremental improvements to the four-step model are
needed in the short-term, because it is often suggested that this
model is an engineering approach to a social phenomena. Another
participant stated that these incremental improvements might be
beneficial in the short term, but were they necessary for long-term
consideration? It is important, was the reply, that long-term
considerations not divert attention from short-term necessity.
Long-term modeling objectives can be served with advanced computing
and mathematical capabilities that were unavailable before.
Several participants supported this view, and the statement was
made that both short- and long-term considerations need to be
addressed by adjusting existing processes and exploring completely
new frameworks for conducting travel demand analysis that go beyond
the four-step process. These new frameworks can incorporate ele-
ments of chaos theory and mathematics and observe how land use,
transportation and travel behavior interact.
It was then suggested that research areas should not be
constrained to data sets collected from the narrow American
transportation experiences. The dependency of Americans on the
automobile constrains the mode choice wi a community. Thus, the
overall transportation experience needs to be considered. Short-
term questions, such as those related to clean air, need to be
addressed; but for long-term economic competitiveness issues such
as the dynamics of the automobile-dependent society, the
metropolitan structure, and the evolution of constraints on travel
behavior all need to be included. Countries with high levels of
13
affluence such as Canada, Germany, The Netherlands, and Denmark
need to be examined. By extending the data set to incorporate
communities outside the United States with significantly different
mode shares, the impacts of pedestrian and bicycle modes and
transit-oriented cluster developments can be better understood. It
was suggested that geographic information systems (GIS) will
support this kind of research because micro-scale land use and
urban form will be easier to incorporate into traditional research
methods.
It was then suggested that there are straight forward ways of
modeling travel and land use (e.g., the incremental travel
forecasting procedure for transit alternatives analysis that is
being used in several cities was mentioned). The procedure uses
long run demand elasticities based on cross-sectional data. Travel
is divided into three components. One is growth in travel due to
the changes which would have happened in the region without the
major transit or highway improvement. The second is the changes in
travel which result from highway improvement and include both land
use redistributions and changes in travel and travel cost due to
the lowered price of travel. The third is diverted travel, which
is how the travel on the particular mode in question distributes
itself among the paths in that mode. In this instance, induced
travel is really caused by the redistribution of land uses and also
by the redistribution in travel as well, including longer trip
lengths and increased trip rates. This can be reduced and
simplified to be almost incremental elasticity-based by applying
single variables.
One participant responded that it is necessary to separate the
ability to model from the necessity of gaining a better
understanding of what is going on in society. This effort may be a
large, data sensitive effort that will not necessarily be
elucidated in these models. A concern was also expressed about the
practice of ignoring certain types of data, simply because the
methods to forecast them are unavailable and, thus, not deemed cost
effective. A concerted effort needs to be made to understand the
current situation and then determine if the models are appropriate.
Two elements need to be distinguished: the societal effects on
travel and the changes being made to the transportation system.
Understanding travel behavior will benefit the comprehension of the
impacts of both these elements on travel.
There are several contextual issues that relate to these types
of questions, one participant stated. there is no clear idea as to
how much can be known in regard to the overall transportation and
urban systems which are so complex with everyone making travel
decisions simultaneously. There are interactions which will never
be taken into account, and it may never be known how well the
models really represent this complexity. No consistent set of
numbers are available to tell how large the model errors are; and,
even if there were, it would be difficult to determine if the
errors were problems in the model, the data, or modelers. Even if
these things were known, it might not make any difference. There
will always be a need for improvement in models, yet it is not
clear when these should be made or why.
There is no question that more research needs to be conducted
to improve the understanding of the issues presented here, one par-
ticipant stated. However, one of the fundamental problems remains
that many models currently in use are well behind the typical state
of the practice. This may be due to a combination of the lack of
finances, lack of staff resources, or carelessness. It was
suggested that by merely bringing what has been learned into the
existing models, great advances would be made.
The relation between work and non-work trip choices and
location was then raised by another participant. In California,
for example, so much emphasis is placed on work trips and location
choice, that a phenomenon has been ignored, that of people making
location decisions that will force them to be auto-dependent for
all other non-work trips. The work trip can be addressed through
HOV lanes and transit facilities that provide better service for
these trips. By choosing to live in areas of single-
14
family housing and low density, an overall travel pattern is
created. Transportation investment decisions make a difference in
these residential location decisions.
A question was then raised regarding politics, travel choices,
and travel behavior. One participant observed, based on
experiences in California, that environmental groups are expressing
concerns about transportation investments that cite development as
the real issue, not whether a trip is new or redistributed. Trans-
portation plays a role in encouraging development. Focusing
research efforts only on redistributed trips will miss the point if
the real public concern is developmental impacts.
General criticisms of the current state of travel models were
offered by several participants. One general plan was described,
for example, that projects three times as much employment as
housing. These figures were generated using arbitrary land use
inputs without using additional transportation input, thus making
the results meaningless. Many large scale models are used
incorrectly too, by not feeding congestive travel times into trip
distributions. This may result in similar VMT numbers across all
development alternatives, even no-build scenarios. It was
suggested that the Environmental Protection Agency and the Federal
Highway Administration set standards for modeling agencies. These
standards should be distinguished between short term and medium
term by encouraging the MPOs to implement land use models and the
long-term applications and improvements of the four-step model.
The question was raised as to how freight movement relates to
the issues being considered. Freight accounts for a large part of
traffic in metropolitan areas where interstate commerce moves into
and out of ports. The trend toward just-in-time delivery is
increasing the amount of product inventory on the highway system
and the amount of truck deliveries. How do capacity needs for port
access and airport connections relate to work travel? Environmental
and economic questions are relevant to both issues.
Several concluding remarks were made, particularly regarding
the non-work trip. One of the reasons that induced travel has not
been measured is a general failure in understanding non-work
travel. Increasing this understanding is a primary concern which
may be addressed by developing methods to measure it more
effectively. As non-work travel is measured currently, it accounts
for up to, 50 percent of peak period travel. Restricting research
efforts to the work trip will not be enough when focusing on peak
period congestion. Non-work travel must be included for
consideration of air quality issues and congestion when studying
the effects of added transportation capacity.
15
Effects of Added Transportation Capacity on Development
Michael V Dyett
By looking back to the transportation modeling activities of
the 19, a clear connection can be seen between land use and
transportation. Planners are now in an age of standards, following
an age of surveys and of models. California law now specifically
requires planners to ensure that the circulation element is
correlated with the land use element. This means more fitting two
maps together on the light table: it involves generating many
iterations of model runs to get the right fit and even then the
improvements must appear affordable. The trend now is to use
different levels of service standards for different land use types,
thus requiring that the circulation element fit these varied
standards.
Cities and other promoters of transportation facilities are in
the land development business, although they often do not fully
understand how transportation capacity affects development trends.
Highway and transit projects are not just intended to alleviate
congestion, which may even be impossible over the long term but are
intended to enable urban development to occur.
Added transportation capacity, both improving the existing
system and creating new facilities and services, may affect several
aspects of urban development. The development location may be
affected by added capacity; the effect could be either a
distributional effect of or a net addition to the region or
corridor. In studies of the Bay Area Rapid Transit (BART) system,
the distributional effects are evident, but there was no net gain
in terms of the competitive advantage of the area. BART affected
the decisions on where to build, but it did not create markets or
add to the overall housing supply.
The type of development can also be affected, particularly
residential versus commercial and industrial. New highways can
increase the viability of shopping centers and mixed use facilities
as these centers are capable of drawing critical masses of people,
up to 100, 000. Highways can also expand the commute shed and spur
housing development. The BART impact studies also revealed a
hedging phenomenon. Potential home buyers sought locations that
would be served by BART at a later date. In this way, added
transportation capacity was used as a form of insurance for the
long term, and developers marketed future BART availability as an
amenity. Development density and intensity could also be affected.
As a site becomes more accessible, there is increased pressure for
higher density development. The Galleria area in Houston, Texas,
is an example of high density development and transportation
capacity. This mixed use area encompasses enough land area to be
ranked as the third largest downtown in the state. Proposals for
new highway capacity could result in 12 freeway lanes.
Added transportation capacity can also affect development
project timing, lease up, and occupancy. Speculation often occurs
before transportation projects are approved and under construction;
this expectation can influence development construction timing or
leasing.
Land use effects are traditionally determined on the basis of
changes in accessibility, as well as mobility. These changes in
accessibility will affect peak-hour trips. A missing link in the
effect of added capacity has been its impact on latent travel
demand, primarily related to discretionary, non-work trips. This
latent demand may induce pressure for new development or
17
redevelopment. In urbanized areas the additional capacity alone
may facilitate or promote development, while in new growth areas a
whole package of facilities, including schools, water, and sewage
and drainage improvements are needed.
The setting in which added transportation capacity occurs also
affects development. Economic growth potential may vary from re-
gion to region, for example, Buffalo compared to San Diego. When
the economic growth potential of an area is low, the growth-
including impacts of a transportation facility are also low. When
there is a strong regional market with a high economic growth
potential, the growth inducements and impacts are greater through
multiplier effects.
Land use policies such as zoning and growth management
requirements limit the effects of added capacity, but they also
enable local governments to capitalize on the benefits. In
Freemont, California, the goal of the city was to control the type
of development adjacent to the BART line. A density floor was set,
and the city waited until the market could meet these requirements
rather proceeding with lower density developments.
The dimensions of new capacity are another important element
when considering impacts. Is the added capacity an incremental
improvement to an existing facility, or is it a new highway
development?
Location within a region is an additional dimension to
consider. If infrastructure facility packages are in place on the
urban fringe, added transportation capacity can induce fairly high
impacts. In an older central business district (CBD), however,
there might be low growth inducing impacts of added capacity.
There are several strategies for dealing with development
impacts. The primary key is effective, long-range, comprehensive,
coordinated land use and transportation planning supported by local
political leaders. Transportation improvements and private
development projects that are consistent within these plans should
not be automatically assumed to induce growth, nor should they be
subject to separate impact analysis for air quality. Also, these
pro" should not be subject to mitigation requirements beyond what
would be a fair share contribution to citywide improvements and
specific off-site improvements not contemplated by the local
jurisdiction's comprehensive plan.
The decision-making process of whether to add transportation
capacity should focus on how to resolve conflicts through multi-
jurisdictional planning. Projects that are consistent with
comprehensive plans and zoning restrictions should also be
distinguished from those requiring amendments or rezoning. The
decision making process should include the following four steps:
1. Design equitable proposals;
2. Facilitate constructive negotiations within the community and
between affected jurisdictions;
3. Make decisions based on plans and packages of improvements,
not individual improvement projects that are not consistent
with land use plans; and
4. Compensate those adversely affected. Two types of questions
can be posed for a research agenda: (1) general issues of
concern regarding development impacts and (2) more specific
questions related to the development process and the role of
added transportation capacity in development decisions.
A general consideration includes determining what criteria to
use where evaluating development impacts. Safety, mobility, land
use compatibility, and the desire to influence modal split are all
elements that could be used. Where there are level of service
standards correlated with land use, how should through traffic be
evaluated in judging local compliance? Under what conditions can
new capacity be added without growth-inducing effects? When will
new capacity contribute to "economies of agglomeration" or, in
contrast, foster more dispersed development? Does it make sense to
distinguish improvements designed to cure existing deficiencies
from improvements
18
oriented towards new development?
A more specific question related to the development process
includes how to determine the developers' perceptions of congestion
costs. Do developers consider congestion a cost of doing business
that is unlikely to affect project lease-up rates? Or, is the
potential for future congestion considered in overall project
value? What is the duration of the development effects that is
attributable to added transportation capacity? In relation to
system performance, are these limited in both geographic area and
in time? Does the perceived improvement in mobility from added
capacity result in a larger commute shed or greater potential
retail market with a long-term economic benefit, or are the results
short term in nature?
Mr. Dyett concluded his presentation with a discussion of a
recent San Francisco Bay area modeling study which dealt with the
effects of the regional transportation plan on land development
patterns in 2010. Over this period, the regional transportation
improvement plan would fund approximately $15 billion in highway
capital costs and $10 billion in transit capital costs. The
Association of Bay Area Governments, by using their model and
studies for the Metropolitan Transportation Commission, found
little difference between the build and no-build scenarios within
existing land use constraints. The Bay area is typified as a
coastal area consisting of highly regulated communities where the
free market does not function in an unconstrained manner. When
land use constraints were lifted in the model, new roads had an
impact on the distribution of growth. In some counties of the
study area, a more dispersed development pattern developed; while
in others there was a tendency toward intense development and
greater accessibility. The study showed that new roadway capacity
could have a greater effect on land use distribution if all land
use constraints were removed, which is unlikely to happen. The
magnitude and the nature of the effect of added capacity was also
shown to be dependent on where the new roadways were located.
Open Discussion
The discussion was initiated by a review of a general plan
assessment conducted for Montgomery County, Maryland, in 1987. At
that time it was found that the balance between transportation
capacity and zoned land use capacity was significantly off. This
imbalance was the result of the common practice in the United
States of allowing a lot of latitude on commercial zoning& in
effect, to give the market the freedom to go where it wanted. The
plan assessment determined that the system could not function
because of the dramatic imbalance between the number of jobs and
houses that was determined by the existing zoning restrictions.
Since the assessment, changes in the zoning structure have
constrained the amount of employment which can be supported. Addi-
tionally, a comprehensive growth policy study which considered
various scenarios for growth was conducted. This study showed that
it would either be possible to (1) support as many as twice the
current number of jobs and houses or (2) support very little growth
within the master plan transportation infrastructure. Either
scenario depended on the kinds of pricing policies, pedestrian and
bicycle accommodations, and travel demand management (TDM) measures
that were initiated. The way in which the comprehensive link
between land use and transportation planning is implemented is
critical to whether or not added transportation capacity induces
growth.
One participant commented on the use of models and the results
of the BART modeling reports. Reservations were expressed regard-
ing the conclusions that only slight differences were found between
the build and no-build scenarios. This result was determined by
the property of the models that were used and that they showed
little response to the transportation system because the models
used for part of the land use forecasting were models that were
heavily constrained by external inputs. The external inputs, such
as housing stock combined
19
with the land use constraints, essentially drove the models and
determined the output The implication was that very careful studies
of model structure and sensitivity need to be considered when
applying them to issues of added transportation capacity.
The question was raised regarding freight movement and
transportation capacity and development issues. Mr. Dyett
responded that freight movement was linked to industrial de-
velopment plans and ports and airports. These transportation
facilities offer an economic advantage for firms involved in the
movement of goods, whether they locate near resources or markets or
are footloose. If transportation costs can be minimized, an
economic advantage can be gained; therefore, firms tend to seek out
and bid up land prices that offer this advantage to the extent that
local and regional plans provide opportunity. For example, some
ports in the San Francisco Bay area have been successful in
attempts to spur land development, increase goods capacity and
throughput, and attract economic development.
Another participant noted that the level of service (LOS)
standard requirements that had been in place in California for
several years, and have been copied to a certain degree in the
Intermodal Surface Transportation Efficiency Act (L%TA), have
probably had more negative effects than positive. The LOS
standards have led to down-zoning and development restrictions
because they are not based on economic analysis that determine the
best, most effective transportation service, but are based on a De-
partment of Public Works process that utilizes little land use or
planning input. In Montgomery County, Maryland, an adequate public
facilities ordinance has been in use for years that uses both
areawide and local area standards for approving new subdivisions.
The county permits more congestion in areas where people have
alternatives to the automobile. Individual subdivisions are tested
to see if they cause local intersections to fail according to local
area standards. Frequently, intersection widenings would be
required which degraded the pedestrian environment that the county
was seeking to improve. In this way policies and LOS standards
often work at cross purposes.
Several questions were posed for general discussion: what
knowledge about land use is needed to measure the impacts of new
highways? What kind of data needs to be collected, and how are the
measurements going to be conducted? It was suggested that the panel
discuss whether or not they were ready to measure the effect of
added capacity; and, if they felt they were not ready, what was
needed to get ready.
One participant suggested that they were ready for
measurement, although the quality of analysis was not consistent
throughout the country. There is an obligation to measure the im-
pacts as there are capital commitments being made with major
environmental implications. The comment was made that one problem
in measuring impacts is that, first, the affected area or region
needs to be defined and matched with an institution. MPOS, for
example, do not always encompass the entire region that will be
affected by added transportation capacity. This will create
difficulties in data collection and measurement.
The issue was raised whether it would be possible to identify
the circumstances under which a project or program would not be
likely to trigger any sort of development or locational effects.
Transportation agencies or air quality agencies can then proceed
with confidence that they will not be subject to litigation based
on unforeseen impacts. Mr. Alan Pisarski replied that others
analyze transportation demand. For example, a retail chain might
analyze how far away people are to one store and then calculate
where the next store should be located. These sources provide
feedback that should be considered when potential impacts are
analyzed.
The discussion continued with a comparison of the American,
Japanese, and European shopping travel tendencies. Americans, it
is claimed, travel greater average distances to shop do Europeans
and Japanese. This is a function of the retail structure of the
country,
28
and the United States has been putting pressure on the Japanese to
break up the "mom and pop" retail structure and allow for larger
regional shopping centers. The Japanese will then become more
dependent on longer shopping trips and larger retail aggregations.
The Europeans, too, seem to be moving towards a reliance on hyper-
markets rather a dispersed retail environment. This creates a
different interaction between freight and passenger systems. The
European experience is demonstrating that by conglomerating the
retail activity, the number of trucks needed to service the hyper-
markets is reduced; but it also increases the number of passenger
trips to retail centers. The policy tradeoff is whether more
trucks in the city are desirable because of a traditional
disaggregate retail structure, or are more passenger vehicle trips
desirable to a regional shopping center? One participant suggested
that because of these issues, the traditional transportation models
need to be adapted to represent the more dynamic system of
interactions between transportation and business.
The United States manufacturing and service industries are
becoming more like the Japanese with an emphasis on the time of
delivery and the predictability of service delivery. This has
different implications for the industry transportation interaction.
An understanding of the change between the private sector and
public investment is necessary to design models for the future.
The two most important transportation elements to the private
sector are bottlenecks and flexibility.
The question was then asked if telecommunications will be
considered to be added transportation capacity. Mr. Pisarski
replied, yes; the advent of increased telecommunications had
influenced the location of business and how traditional business
depends on transportation, for example, with just-in-time delivery
systems. One of the problems with telecommuting, however, is that
by eliminating the trip to the downtown office, and its available
amenities, the likelihood of additional trips from home for errands
increases. One home-to-work trip downtown is replaced by several
non-work trips.
Several issues regarding the political and social aspects of
transportation planning and the impact of added capacity were
discussed. The difficulty of considering local zoning practices
and changes in transportation modeling was one problem, considering
the economic inefficiency of local governments. Many of the
western states use zoning by initiative, and its impacts are often
impossible to predict Most models, too, are developed around the
assumption of single-worker households optimizing their location
with regard to a single work site. Social conditions have changed
considerably, and the two-worker household is prevalent. It was
noted that housing prices had risen dramatically, too; and people
might be choosing their home location first, then their job
location.
The question was raised at what level, project or areawide,
should transportation impact models be developed. Traditionally
the areawide scale has been used but concern was expressed about
the ability of any model to address the small scale impacts of
mixed use development and the importance of the non-work trip.
The reply was that there was a considerable amount of new
research being done on two-worker households and housing location
choice, but little had been implemented in practice. The question
of which is chosen first, housing location or employment, is also
being studied, as is the importance of recreational opportunities
and housing location decisions. There have been few attempts to
link these studies with the transportation models, although housing
decisions could be an important part of these models. There has
also been recent work on business location decisions of footloose
industries, the role of telecommunications in industrial
specialization, and the breakup of firms. Concern was expressed
for the inability to define the limits of a study area as well as
the time frame needed for a research program. Only by setting
limits can progress be made in evaluating the impacts of added
capac-
21
ity. One of the problems with limits, it was suggested, was that
modeling tends to look at things that happened five or 10 years
ago. The impacts of telecommunications are significant
at this point in time; but they will be even greater 10 years from
now and even with a considerable investment in research efforts,
the questions will continue to evolve. Rapid changes in housing
and business location decisions, therefore, need to be considered
in modeling design.
The comment was made that there was a distinction between
short-term research modifications and the long-term research
agenda. There can be modifications made to short-term impact
studies that will address changing technology on a project-by-
project basis. However, for the long-term agenda there is a lack
of understanding as to the potential impact of telecommunications.
There is a dual problem: one dealing with the necessity for short-
term modifications and the other dealing with the long-term
understanding and incorporation of rapid changes in the models.
It was suggested that for the short term, modeling will
continue as it is already being done; there is little that can
change the focus. The long-term agenda is the one that the confer-
ence should be concerned with in seeking improvements to modeling
tools and understanding. There was general agreement among par-
ticipants as to the necessity for a long-term focus on the issue
but also on encouraging the simultaneous advancement of the current
state of practice and the improvement of the state of the art in
assessing the effects of added transportation capacity.
22
Other Effects: Institutional and Financial Context
Sheldon M. Edner
The decision-making process inherent in all aspects of
transportation planning (impact studies, transportation systems,
travel behavior issues, and land use planning) falls within the
context of organizations. This is a concept of decision making in
more than three dimensions. This multi-dimensional characteristic
of decision making increases the number of variables available for
travel behavior prediction.
Those who must make the decisions or introduce them into the
transportation processes are the politicians in the urban areas
around the country. They must make decisions regardless of the
reliability or accuracy of transportation models or knowledge of
associated issues such as business location decisions. These
decisions are made regardless of the state of planning or modeling
practice at any one given point in time. How does the
institutional system operate, then, in which these political and
transportation decisions are made? Implicit in this discussion, in
terms of the planning paradigm, is that regardless of how
successful the plan, the integration between transportation, land
use, and environment is critical. The institutional legislation of
the Intermodal Surface Transportation Efficiency Act of 1991
(ISTEA) and Clean Air Act Amendments of 1990 (CAAA) has reinforced
this. In that context, it is necessary to consider the current
organizational decision making process.
In most urban areas the context for making transportation
capacity decisions is not an integrated process. Indeed, most of
the institutional context is extraordinarily fragmented and, in
many areas, getting worse. Each of the organizations within
metropolitan areas has a piece of the pie and feels driven to
implement it to their own best interest. San Francisco is one
example of this fragmentation. In monitoring a project for Federal
Highways, which includes the issue of how the Metropolitan
Transportation Commission (MTC) is going to react to and carry out
the new responsibilities it will have under ISTEA, major problems
have developed. As a result, MTC has been talking to a whole new
cast of institutional characters beyond those with whom it
traditionally has dealt. All affected participants will talk about
how to integrate not only MTC's planning function but also
operations issues such as linking together planning and operations
to produce the reduction in air emissions which is expected of the
transportation side of the equation in metropolitan areas.
One of the most enthusiastic new institutions that MTC is
talking with is the California Highway Patrol (CHIP). Becoming
involved in the whole process of decision making in the Bay area is
extraordinarily important to CHP because it means they finally are
given an opportunity to have some input into the design and
development of the transportation system which they must control.
Urban areas are more and more fragmented today than ever
before. The last decade has essentially been one in which more
diversity has emerged in the metropolitan areas with more
institutional fragmentation. The experimentation with the private
sector involvement in joint development and privatization of trans-
portation services has created not only a larger private role but
also many more quasi-governmental and governmental agencies. An
examination of the U.S. Census of Governments shows that the number
of governmental units across the country is increasing by
approximately 3, 000 units of government every five years. The
primary growth takes place among special districts, the single-
purpose, uni-dimensional gov-
23
ernmental entity with its own resource base which has
responsibility, for example, for sewers and water, in one
particular area. The process of identifying the working relation-
ships between these organizations and what they do is more
difficult as a result of this fragmentation.
Transportation, in the context of fragmentation, is a single
activity that must fit into a much broader set of tradeoffs that
are made by a number of organizations working simultaneously
towards their individual ends. They do not all work together
easily. ISTEA's Section 134 MPO requirements specifies a
coordinated metropolitan planning effort and does not even suggest
all of the necessary players. Traditional MPOs have been
representative of general purpose governments, resulting in the
exclusion of a number of individual agencies who, in one way or
another, have been responsible for either developing part of a land
use planning process or implementing zoning, financing systems, and
other aspects of the support systems which make transportation
systems operate.
The context of transportation is, in this institutional
environment, very fragmented. This fragmentation has led to the
basic problems confronting many metropolitan areas and also has
contributed to the difficulty of defining induced transportation or
additional trips. Because not all organizations share a common
definition of what constitutes a trip or trip purpose, each
organization may view an additional trip in a very different way.
As a consequence this inconsistency makes a determination of
whether or not an additional trip is good, bad, or indifferent
Portland, Oregon, for example, is zoned for a much higher density
than the development it currently exhibits. Those zoning plans are
already in place and have been for years. Now that the real estate
market is growing, developers are taking advantage of the potential
for higher densities and are demolishing single family
neighborhoods and building row houses. Residents in those areas
are concerned because they do not think the change is appropriate,
and they want to maintain the quality of life they have come to
expect. The City of Portland's view, however, is to support the
higher density zoning opportunities. In addition, other
jurisdictions around the metropolitan area have responsibility for
parts of the infrastructure process which are not necessarily
working in concert with the City of Portland. As a consequence,
the whole process has become complex and people are suing one
another. The transportation system is becoming part of that
complex process in terms of deciding where to build additional
capacity.
In effect, there is a ripple effect out from some of the
individualized decisions. A number of effects ripple out from
improving transportation in a corridor, such as right of way
acquisition in terms of the immediate corridor. How far out past
the immediate corridor should impacts be considered? The whole
corridor preservation component within the current legislation is
going to test that proposition; because when an individual project
is sited, it may be obvious where to buy parcels of land for
speculative purposes. But preserving the land for environmental
reasons may constitute the switch to a new corridor, possibly one
with a fixed guide way improvement. Broader analysis beyond the
center point of the ultimate right of way might be required which
would involve a wider range of institutional actors with individual
responsibilities for decision making in metropolitan areas.
Another component of the institutional context of added
transportation capacity involves tying in the operating elements.
Over the years, operating agencies have been left out of the
transportation planning picture. In many cases they are after-the-
fact participants. The Tri-County Metropolitan Transportation Dis-
trict of Oregon (Tri-Met) got involved in planning for the Portland
light rail line system because they recognized, in the early
1970's, that they were going to be left to operate whatever system
was developed. Tri-Met hired a consultant to make the case for the
system they wanted, in part, because they wanted to participate in
its ultimate operation. Other organiza-
24
tions have not taken that kind of aggressive leadership; and, when
given the responsibility for system operation, they have not been
prepared. This has created a circumstance where the capacity of
the system has either been degraded, or enhanced, in an unforseen
direction.
Added capacity also raises a question of design standards. If
land use planning is used to reinforce transportation systems so,
too, should design components in order to integrate all elements in
one overall package. Again, the institutional context within which
that takes place is extraordinarily fragmented and continues to
remain that way.
What has developed is a more decentralized decision system
that somehow must implement the concept behind land use planning
and its integration with transport in the environment in a holistic
fashion. The implicit message is the sort of normative
underpinning of planning that all things should be rational and
integrated. But, in the real world, it is not. The institutional
decision processes are decentralized and fragmented; and, as a
result the individually pieces do not necessarily fit together.
Non-communication occurs the most and a dynamic tension exists
between the developing suburban fringe in many metropolitan areas
and the traditional core. The exurban fringes outside a
metropolitan jurisdictional boundary will often act independently
of one another with a tendency to create pressures to develop
transport systems to serve their perceived locational advantage.
From a political and a broad development perspective, this fragmen-
tation tends to reinforce the notion of decentralized and
disaggregate developments that is evident around the country. It
also begins to manifest itself in system financing, whether
transport, housing, or whatever. The result is an incredible
amount of competition for the available financing resources within
a given metropolitan area. The disaggregate decision system is
mirrored in the financing process. Getting all the players to
agree on what kinds of projects ought to be built in a given
metropolitan area and to pool their resources to do so is an
extraordinarily difficult political process. This lack of regional
cooperation leads to the situation represented in the approximately
530 individual projects that are included in the ISTEA legislation.
Those projects exist in part because they were not funded locally
and, to circumvent local roadblocks to financing, were elevated to
the level of national crisis in order to be included in the
legislation.
What is happening then is a disaggregate system g to pool
resources in a way that it is not prepared to do. MPOs which have
the comprehensive oversight for developing transportation plans
have not been operating agencies or, in most cases, funding
agencies. They have been temporary planning organizations which
have had very little institutional context or experience with long
term projects and very little authority. As a result, they are
going to have to develop additional authority to make se collective
metropolitan decisions which to go into reinforcing the
transportation programs that need be implemented over the next few
years.
Another dimension to this disaggregated, fragmented metropolitan
institutional context s an inconsistent time horizon. Each of the
organizations operates in its own format and time horizon, which
are often different than any other participating organization. To
suggest t there is a difference between the transportation planning
and air quality planning process, in a technical sense, also
suggests differences in terms of timing. Transportation plans re
built around the life expectancy of facilities, in some cases,
management systems; whereas air quality life expectancies and time
horizons are built around a different kind of context. As a
result, there is an extraordinary difficulty in simply bringing
together that timing in a way which allows the participating
organizations to work together. By also integrating the land use
planning process, which has an ever longer horizon in some
respects, the result is an integrated planning process with entire
frames of reference in contexts that are not necessarily
consistent.
25
Within all of this institutional fragmentation is the local
politics of a given metropolitan area. Each metropolitan area has
its own unique way of doing business. In the Portland metropolitan
area the downtown central district was preserved, unlike many other
metropolitan areas, based on a significant effort which managed to
improve the quality of the downtown. This area is showing signs of
deterioration, however. Competition is beginning to emerge from
suburban areas which are saying, "We gave earlier, it is our turn."
The result is a whole new set of political dynamics playing out be-
tween coalitions of downtown developers who want to reinforce the
investments made 10 or 15 years ago and the developers on the
suburban fringe who want to exploit undeveloped areas and profit
from those opportunities. Those coalitions are dynamic and are
affected by a broad range of factors including the state of the
economy. Unlike much of the country, Portland is a booming real
estate market and, as a consequence, is experiencing a great deal
of development.
Other intervening issues also interact in any given
metropolitan context. Portland has just built a convention center
but does not have a supporting convention center hotel in place.
This development is tied to its integration with the transit system
and the rail fine, as well as being served by various highway
corridors. Regardless of the broad general issues of concern with
regard to transportation, making that convention center work is a
key component of what is going on. It will continue to be a key
component, at least for the City of Portland, even though there is
a proposal existing in one of the suburban counties for a new
sports arena to serve as a replacement for the downtown coliseum.
Existing big ticket facilities tend to dictate a large part of what
goes on in a metropolitan area largely because the decisions are
made by different partners. A justice center was built in downtown
Portland using federal highway money because the construction of an
outer belt adversely impacted a decrepit jail. That was the basis
for the construction of an award-winning justice center funded, in
part, by the Federal Highway Administration.
Also unique to the metropolitan context are the social issues
that exist. The social environment of many metropolitan areas is
changing radically. It has been suggested that it is necessary to
take into account the differences in transportation behavior in
terms of what kind of trip making decisions people make. The
demography of Portland is a unique example. Demographics show that
people start out as a family in the center core of the city. When
they marry or when they reach a point of creating a household, they
tend to move to the outer areas of the city boundaries. When they
have a family, they move out into the suburbs. When they are done
rearing the family, they move back into downtown. The notion that
trip making behavior over the fife of a family is going to remain
constant is also open to question. Each metropolitan area,
depending on the character of the downtown and the overall
livability of that metropolitan area, has its own unique and
dynamic trip making behavior patterns.
Los Angeles raises another social question with its diversity
of ethnic backgrounds. People in the lower end of the economic
spectrum are finding it easier to afford automobiles, to a certain
extent, but are now being squeezed in an environment of intense
immigration with major impacts on schools and other social systems.
The diversity creates even more demand on existing transportation
systems and changes the mix of social systems and social service
systems. This will have to be a factor taken into account by
transport systems.
The relationship between transport improvements in a given
corridor and the overall institutional context that exists in the
metropolitan area is a synthesis. In some senses, the given, which
planners work with in developing overall transit plans for urban
areas, is the community value structure that they are trying to
enhance with the planning system. This value system is not an
integrated whole but is put together by a number of different
institutional players in a given metropolitan area. Recogni-
26
tion of this gave rise, in part, to ISTEA's section 134 planning
requirement that requires an MPO to provide a forum. The process
of defining community values has not gotten any simpler or more
homogeneous over the years, even with the presence of the Section
134 requirement. That led to part of the rationale for making the
institutional process of the MPO even more extensive in terms of
authority granted, for example, to make decisions based on the
authority to withhold federal funds. As a result, the ability to
articulate community value on a metropolitan-wide basis and then
achieve it through planning processes drawn together in terms of
transportation and land use, is still open to question. The
process of land use planning is made that much more difficult
because of the important question, what kind of urban form is
desired? If there is no ideal or clear cut sense of the goal, or a
holistic process of achieving it on a metropolitan level, the
efforts, in terms of siting transport systems particularly within
the context of an environmental dimensions will be much more
difficult over the long term.
The argument can be made that a national urban policy exists
in disguise. It appears in the context of the CAAA and ISTEA.
This raises broad-based questions which deal with a wide range of
issues taking into account transportation and housing and
investment in a synthesizing way within the context of these two
pieces of legislation and in an institutional context of fragmented
and decentralized metropolitan areas.
In the short term there are not going to be any Changes in the
process of transportation planning.
Open Discussion
The discussion was initiated by a description of the
interstate substitution process as an example of a way to overcome
the inertia of competing jurisdictions. The interstate substi-
tution process allows different areas to trade interstate freeway
segments in order for each
area to gain from the overall process and allows for financing to
be shifted from one project to another. The process was
responsible for the development of the Portland light rail project
when over 140 other projects were combined in the process, and all
affected parties gained something. For a substitution process to
work, individual jurisdictions need to be aware of what they would
gain by participating and, for those uninterested jurisdictions,
there needs to be incentives to encourage participation. These
incentives can be either positive, in the form of local financing,
or negative, in the knowledge that other jurisdictions, by
participating, will have an advantage over or a negative impact on
the non-participant It was suggested that there is a limit to the
coordination of affected jurisdictions, however. As a broader cast
of characters is required by legislation such as ISTEA and the
CAAA, making sure that all the organizations understand the
advantages of participation will be extremely important.
Efforts have been made to broaden the geographical definition
of a city in order to incorporate a larger tax base that will
support a deteriorating inner city. The question was then asked if
there were any similar attempts being made to increase the
dimensions of an area to include more institutions that would be
potential participants in projects adding transportation capacity.
Mr. Edner replied that in some cases legislation may redefine
metropolitan areas. The boundaries of an MPO will traditionally
include all urbanized areas, but it might be different from the
census definition of a metropolitan statistical area or
consolidated metropolitan statistical area. In defining an area of
ozone nonattainment, for example, the boundaries may be different
depending on whether or not the governor of the state decides to
include nonattainment areas outside the traditional MPO boundaries.
Some metropolitan areas might also have more one MPO.
There are few places with formal land use transportation
models, one participant claimed. Often, the chosen method of
transportation forecasting involved borrowing land use forecasts
27
and simply applying different transportation scenarios. This
method needs improvement because the link between the two elements
should be strengthened. Land use forecasting should incorporate
transportation improvement impacts down to the local level.
Alternative scenarios need to be developed that extend beyond
current conditions, perhaps including the impacts of transit or
transportation demand management strategies. Various investment
circumstances and pricing changes, too, should be considered in
transportation and land use models.
It was also suggested that the effects of the fragmented or
multiple levels of jurisdictions need to be understood as well,
regarding their impact on transportation. One of the problems
associated with that approach is that even if all jurisdictions
within a region try to cooperate, their individual levels of
understanding will often be incompatible. Differences in under-
standing will be compounded by different levels of financing,
analytical capacity, and data collection. This potential conflict
presents the question of how to bring an entire metropolitan region
together with the same level of competence to approach the issue at
hand. A related concern was, given the potential disparity between
jurisdictions, how can the EPA assure any level of overall
conformity? One suggestion was that an environmental information
system (EIS) could be implemented for the overall region to analyze
conformity on a program basis rather than on a project-by-project
basis.
Transportation professionals, one participant contended, need
to encourage changes to the institutional structures that currently
act as impediments to planning and implementing added
transportation capacity. Developing the data to support changing
this fragmented institutional structure will be an important part
of the research agenda recommended by the conference. Unless
changes are made, the fragmented structure will continue to
discourage coordinated land use and transportation planning
efforts.
One participant asked what, then, was needed to develop the
necessary data to support changes in the institutional structure.
It is important, one participant replied, to first look at what the
current institutional structure had done. A study of the Washington,
D.C., metropolitan area that was prepared for the Transportation
Research Board showed that in the sub-regional planning process, three
major local jurisdictions had revised comprehensive plans that contained
inconsistent transportation and land use elements. This example clearly
showed the extent to which non-cooperation would have significant impacts
on any future development at the regional level. The level of
decision making needs to be equal to the level of impact. One
solution would be to give local governments responsibility and make
them accountable for issues of consistency. By making the
institutional framework responsible, and self-policing the
decision-making process will be more explicit and less vulnerable
to inconsistencies.
Another point was raised concerning the difficulty in actually
defining the type of urban form that was currently in place. How
does the existing urban form relate to the institutional structure,
and is this urban form a response to social pressures or
institutional preferences?
An ongoing research project was described where the influences
of institutional factors on transportation and development patterns
are being considered. In collecting an international data set and
evaluating the travel behavior differences between European
countries, an attempt is being made to identify and evaluate the
institutional factors. Different policies of housing and business
investment also affect location and transportation decisions. It
is necessary to stress the long-term nature of comparative
institutional research, as well as the necessity for a systematic
approach, to ensure that all key variables are identified.
One element of institutional interactions is the concern for
system costs. Each institution wants to select the system that
will produce the greatest benefit at the lowest cost. To relate
this to transportation capacity, it is necessary to
consider various alternatives and the costs associated with each.
Ultimately, the challenge of the conference is to consider how to
convey total system costs and alternatives to affected
jurisdictions and the public itself. Fundamental to this task is
identifying the strategic options of added transportation capacity
and developing tools and models that are policy-sensitive at the
macro- and micro-system levels.
The temporal context for the institutions which do that kind
of planning will be long term, and transportation planners are
still going to have to try and approximate it and deal with it.
What is important is determining the relationship, over the long
term, of land use planning, environment, and transportation, and
integrating, synthesizing, and making them work holistically in a
decentralized, fragmented metropolitan area.
29
Day Two: How to Address the Problem
The opening remarks for the second day of the conference were
presented by Dr. Gordon Shunk, Manager, Urban Analysis Program,
Texas Transportation Institute. In his comments he restated the
original intent of the conference: to identify the principal
impacts of added transportation capacity and to determine how to
study and incorporate the impacts into models and the planning
process. He then summarized the main points from the first day of
the conference:
- The impacts of added capacity need to be identified before the
modeling process can begin.
- The principal impacts include the growth-inducing effects of
added transportation capacity.
- The relationship between travel, air quality, and development
needs to be understood and incorporated into the planning process.
- Environmental considerations need to be merged with
transportation planning to ensure that two separate planning
processes are not addressing the same problems.
- Added transportation can spur development, and new development
can cause redistribution of traffic.
- The impacts of added capacity are conditioned by social
changes, which greatly affect travel behavior.
- Several questions were raised during the initial day of the
conference and were presented for further consideration:
- Will added transportation capacity reduce or increase
congestion and air pollution?
- What elements of the transportation modeling process need to
be changed? Are the distribution mode choice and assignment
models adequate?
- Are there significant latent demand or induced traffic impacts
that need to be addressed?
- Should the development and redistribution effects of added
capacity be considered key elements in the analysis process?
- Does the present lack of information on latent and induced
demand imply that these impacts are, in fact, insignificant?
The following recommendations were presented based on the
presentations and discussions from the first day:
- It is important to consider the negative as well as positive
impacts of added capacity in any further research.
- More analysis of the extent of impacts needs to be conducted,
specifically in determining spatial dimensions and timing
(e.g., when the impacts occur and for how long)-* Better
information on the effects of added capacity needs to be
collected but should not be limited only to data for which
forecasts can be conveniently developed.
- The effects of added capacity on freight movement need to be
part of the research agenda.
- The effects on non-work travel and off-peak travel need to be
considered, as well.
Environmental Effects of Added
Transportation Capacity
John H. Suhrbier
The presentation on the environmental effects of added
transportation capacity is divided into five main sections: general
environmental concerns and issues, comments on the Clean Air Act
Amendments of 1990 (CAAA), description of a land use project in
Portland, Oregon, description of project involvement with the State
of Washington's legislative transportation committee, and comments
on the next generation of travel demand models.
The two levels of environmental concerns are national and
local. National environmental concerns include wetlands
degradation, hazardous waste, air quality, and climate change.
Local environmental concerns include community character, open
space, air quality, and the not-in-my-backyard (NIMBY) phenomenon.
The influence of both national and local concerns on public sector
decision g continues to increase in significance, and transporta-
tion professionals need to be responsive to the kinds of solutions
that are being developed in response to these concerns. One
response is that new and expanded transportation facilities are
needed, particularly intermodal facilities. Airports, transit
stations, and marine and freight ports need to be considered as
well as access transfer facilities.
In order to maintain environmental credibility, existing
facilities must demonstrate maximum efficiency before proposing new
or expanded facilities. This involves implementing such measures
as travel demand management (TDM) and, possibly, congestion
pricing. Transportation analysts must predict the impact of these
solutions. At a recent meeting of the National Association of
Regional Councils during a discussion of employer-based trans-
portation programs, a comment was made that these programs were not
worth discussing because they could not be analyzed by the tradi-
tional four-step demand models. The response was that perhaps the
four-step demand process was irrelevant because it could not cope
with the policy alternatives available today. This exchange
illustrates how important it is that the analytical capabilities of
the transportation professional be enhanced to serve the needs of
current national and state legislation.
The traditional way of discussing the CAAA is to list the
legislative requirements. There are, however, general analytical
requirements that need to be considered. One analytic element is
the base year and future year emissions inventory. Inventories in
many areas win need to be developed on a spatially and temporally
disaggregated basis. Emissions will be examined on an hourly basis
over an entire day, which is not consistent with travel demand
approaches. Regional vehicle miles traveled (VMT) need to be
projected on an annual basis and then the VMT projection must be
monitored. It will also be necessary to analyze transportation
control measures (TCMs). The CAAA also places an emphasis on
market-based economic incentives which will require analysis.
Emissions resulting from increases in VMT or vehicle trips
will need to be monitored, requiring a new set of analysis
techniques. How will congestion be measured, and how will it be
monitored? What is an appropriate measure of congestion on a
regional level? How will vehicle occupancy levels be measured in
response to employer trip reduction ordinances? These questions,
raised by the new air quality legislation, reinforces the need for
new analytical techniques.
The issue of conformity and the CAAA suggests a whole new area
of analytical requirements. The emissions levels from adopted re-
33
gional transportation plans and state transportation improvement
programs (TIPs) need to be consistent with the mobile source
emissions estimate contained in the state implementation plan
(SIP). These are the levels against which conformity is measured.
Conformity will be monitored at the system level, or for entire
programs, rather a project-by-project basis. The changes in
conformity monitoring raises several questions. What is the cost
in time required to do a legally defensible conformity analysis?
Are existing model systems sufficiently accurate on a regional
basis, not just a CBD radial highway basis, for purposes of a
conformity analysis?
New analytical requirements will also be necessary considering
the TCMs recommended in Section 108 of the CAAA. These
recommendations include developing high occupancy vehicle lanes,
trip reduction ordinances, park and ride facilities, and flexible
work schedules. How will the effectiveness of these measures be
analyzed wi the context of transportation planning? In many cases
it will not be possible to utilize the standard four-step network
analysis model sequence. It will not be satisfactory, either, to
assume that empirical experiences from isolated analyses of TCMs
can be transferred to any other situation.
Existing transportation models must be enhanced and new
analytical capabilities need to be developed using pivot point
analysis, elasticities, or statistical regressions based on
empirical data. To improve existing model systems it is important
to know what variables influence highway vehicle emissions. The
month and season is an important variable: ozone is a problem in
the summer, carbon monoxide in the winter. Transportation
analysts, however, traditionally look at spring or fall for a
typical sample day. The time of day is also critical, considering
the emissions impact of non-peak and non-work trips throughout the
day. The standard measurement is VMT, but it is also important to
consider whether the emissions are from cold starts, hot starts, or
are running stabilized emissions. Estimations of vehicle speed are
typically not very accurate in network models; and variables such
as acceleration, deceleration, and vehicle operating conditions are
often ignored. Important vehicle characteristics to consider are
vehicle type, fuel type, vehicle age, vehicle maintenance, and
mileage. The location of emissions, too, should be analyzed; where
emissions occur is important, whether they are in the CBD, suburb,
or elsewhere. For example, it is customary to criticize park and
ride lots which can be effective in reducing VMT and running
emissions, but they do not necessarily reduce trip end emissions
and trip start emissions at the facility.
A highway construction proposal in Portland, Oregon, can be
used as an illustration of the necessity for new analytical tools.
The proposal is for a circumferential highway in the
34
southwest region west of Beaverton, extending from Interstate 5 in
the south up to Highway 26, near Hillsboro in the west This
corridor is approximately 15 miles from the Portland CBD and is
currently at the edge of the developed urban area.
Two important aspects of Portland distinguish it from other
urban areas around the country. First, there is strong interest in
growth management aspects and legislation. And, second, excellent
cooperation between the environmental community and the local,
regional, and state agencies involved in transportation projects
exists.
Two basic objectives drive this project. The first objective
is to evaluate a set of alternatives to the proposed western
highway bypass and to coordinate this with the Oregon DOT and
Portland Metro. The alternatives include land use actions, i.e.,
observing regional growth patterns and specific small scale
activity center developments with a focus on developing transit and
pedestrian-oriented designs. The alternatives are also being
considered within a broadened context of transportation upgrades
for existing roads, transit facilities, travel demand management,
and bicycle and pedestrian facilities. The second objective is to
determine the appropriate analytical tools that will be effective
within this broadened scope. This project uses an interactive and
iterative land use transportation analysis system. The specific
land use model is Pus DRAM/EMPAL gravity-based models. These two
models are linked together in a model sequence with an iteration
sequence of five year intervals where the transportation results of
one iteration are used to influence the estimated distribution of
land use activities, housing, and employment in the second
iteration.
Several products will emerge from this process including a set
of land use development and transportation proposals. Another
product will be an advanced set of models. By simulating the
effects of added transportation capacity on emerging development
patterns, it will be possible to consider whether there is an
alternative to new highway construction. Finally, proposals are
frequently presented in terms of a "what if" scenario. For
example, if a
proposed development is transit and pedestrian oriented, is new
highway construction desirable, as the land use design encourages
transit use and walking? New simulations and model enhancements
resulting from the Portland project can be used in analyzing this
of scenario.
A recent review project for the Washington State Legislative
Transportation Commission further illustrates the need for
analytical improvements in response to environmental
considerations. The project reviewed the methods that have been
used for programming and prioritizing transportation actions.
Washington's methodologies are considered to be among the best in
the country. However, the review revealed several areas where
improvements should be considered. First, the procedures need to
be responsive to a broader range of policy concerns. Two specific
areas identified were growth management and air quality; these need
to be treated in a consistent manner. Intermodal coordination
needs to be expanded beyond the highway programming process to
include other transportation facilities. Investment tradeoffs need
to be examined. One tradeoff would be between preserving existing
highway and transportation facilities as opposed to increasing
capacity. In reviewing project alternatives, a broader range of
investment options should be considered. Finally, these
programming and prioritization procedures needed to be modified to
respond to increased funding alternatives and increased strength in
the regional decision-making process.
The Washington review shows a shift from the traditional
development of fixed transportation facilities plans to more
flexible alternatives that include the possibility of introducing
new technologies. A more strategic management of existing
resources and a consideration of a variety of factors on an equal
basis, such as freight and passenger movement, open space, air
quality, and economic development has emerged. The final
implication is that these factors must be evaluated in a
quantitative manner, not just qualitatively at the programming
stage. To do this effectively requires analytical improvements in
transportation modeling.
Mr. Suhrbier concluded his presentation with comments on the
next generation of travel demand models. There have been many im-
provements to the four-step modeling process over the past few
years, particularly in its adaptation to microcomputers and graphic
technology. However, transportation planners still use the same
four-step process with the same set of models. This situation
presents many questions regarding travel demand models. Is it time
to introduce some substantive improvements to the individual models
and to the way they are connected? Is it necessary to provide more
feedback from traffic assignment into mode choice distribution and
generation? Can a broader range of housing and demographic
variables be incorporated into the model structure of individual
models?
The next generation of travel demand models might consider
expanding the range of policy sensitivity, integrating geographic
information system technology, and incorporating travel demand
management measures. The switch to microcomputers has initiated a
decline in model standardization. Will it be feasible to continue
to develop an overall standard model system or to concentrate on
developing a set of building blocks from which different model
systems can be developed that consider regional attributes?
Considering all these possibilities, the set of transportation and
analytical capabilities that will exist five, 10, or 15 years from
now will look very different from the standards of today.
Open Discussion
The discussion session opened with general comments and
questions regarding the Portland, Oregon, project. The comment was
made that the project was focusing on urban design options that
incorporated transit- and
36
pedestrian-oriented developments. This was different from
traditional suburban development options that were exclusively
residential and encouraged automobile use. How these design
options would blend with the existing urban fabric was being
considered in the study project. This focus created a two-scale
project scope to look at transit- and pedestrian-oriented
developments; one project scope was macro-oriented, and the other
was micro-oriented. One important outcome of the Portland project
was the comparisons of "visions" of future land use with model
results and the attempts to reconcile these two parts.
One participant remarked on the difficulties presented by the
questions of scale. Much of the land use visionary planning that
has been done at the micro-scale, for example, by Peter Calthorpe,
is not easily incorporated into conventional models. The analysis
and literature on pedestrian-oriented developments (POD) and
transit-oriented developments (TOD) claim that lower vehicular trip
rates can result, but these studies do not answer the basic
questions presented at the conference. One of the questions is, if
a TOD is built with neighborhood shopping, will people actually use
it; or win they drive farther to the supermarket to save 20 percent
off the neighborhood market prices? This trip might be at off-peak
hours, but it might also occur during peak hours. How to incorpo-
rate these issues in the models is problematic.
The question of institutional interactions in the Portland
experience was also raised. Sections of the proposed road are
outside the metropolitan growth boundary, and there has been little
coordination between regional policy and state agencies. Similar
issues were raised in Florida, it was noted, which resulted in
explicit revisions in the state growth management legislation
specifying that agencies had to develop plans that were part of the
entire state-coordinated planning process.
Another participant said that the Portland proposal emphasized
the link between transportation capacity increases and travel
demand. The study was designed with a scenario framework for
analysis which is important when considering transportation and air
quality conformity questions. A key issue was that alternative
visions of the community needed to be considered, as the current
trends in western Portland would not be sustainable in the future.
Alternatives to a major increase in highway capacity in the region
needed to be considered. These alternatives incorporated increased
bicycle and pedestrian capacity in the community. One of the
important findings of the study maybe how much TDM measures have to
affect travel prices in order to get the land use models close to
replicating the visions.
The question was raised as to what the impacts of the Portland
proposal were and how they were going to be measured. The main
impact would be how development would occur as a result of
alternative transportation investments in transit and highways.
Other questions would be how that would affect the distribution of
housing opportunities and employment. Would there be significant
variations in housing locations if transportation options were
provided?
The key to making community scale developments work would be
the success of a community shopping facility, one participant said.
This was one area where further research would benefit modeling
activities. It was then suggested that another area of potential
research is housing price response to transportation investments.
This response should be incorporated or considered in future
modeling systems.
The question was presented regarding how transportation
capacity affects development decisions. What, for example, are the
costs of intensification? Missing in the current models, it was
suggested, was the connection between capacity and development,
specifically, the ability to project the reaction of developers to
added capacity.
One participant said that the focus of the development and
transportation interaction was increasingly centering on the
jobs/housing balance. The closer people are to their jobs, the
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more travel can be minimized. However, studies in Great Britain
imply that a minimum distance between housing and employment is de-
sirable; so perhaps further study of this relationship is needed.
The discussion then focused on the need to examine the
forecasting ability of existing models. No serious research has
been done since 1980 on the reliability of the forecasts. Part of
the problem is the unavailability of complete historical network
data sets on which to base a study. It was suggested that there
had never been a great deal of concern regarding model testing on a
systematic basis and understanding what the capabilities of the
model were under different circumstances. One participant replied
that, in fact, most modelers knew of the limitations of the tools.
It was then pointed out that one problem with modeling is that
the actual facilities being built would last for 10 to 50 years.
How can a dynamic world be incorporated into models dealing with
long-term facilities? Fuel prices will vary drastically, as will
human values. Twenty years ago there was little concern for
environmental issues. For this reason, the five year iterative
approach to modeling as used in the Portland study would be
advantageous. An example of this problem could be found in airport
planning. It might be 10 years before an airport is built, and
then it will be in use for the next 20. How do elasticity and fuel
prices fit into this scenario for modeling purposes? The
traditional four-step model would not be adequate for this
illustration. Perhaps a solution would be to incorporate micro
models for short-term project impacts and then use macro models for
the long-term analysis.
It was recommended that micro-scale planning and its effect on
trips should be one of the research recommendations from the
conference. Specific questions should include the effect that
employment and residential micro-planning have on transportation
capacity and the effect that pedestrian-oriented development has on
capacity?
Additional research proposals could be developed from the 1990
US. Census data on metropolitan area journeys to work. This data
supports research on the time element of added capacity impacts.
Capacity improvements over 10 years for individual metropolitan
areas can be analyzed, focusing on the impacts of small area
developments. Development types could be classified as high,
moderate, or low growth for time series analysis. Capacity
improvements under different institutional frameworks could also be
studied. Whether or not the local jurisdictions are amenable to
development and added transportation capacity has further
implications for modeling.
It is important to understand who in the household works and
the location of the work place in relation to the number of total
trips made per day. High tech industries, for example, now employ
many of the lower income workers in a family, placing them in the
overall transportation stream. These workers may not show up on
the primary work estimation process used today. Two people per
household that commute to work and the housing location decision
resulting from multiple commutes have impacts on the transportation
system.
One participant then discussed the importance of not
separating transportation and development policy from forecasting
efforts. The consequences on transportation capacity from either a
municipal growth policy, or an anti-growth policy, a high density
development policy can be significant. The housing market is a
crucial element of growth policies. Housing costs, proximity to
employment, and the types of potential occupants impact the
transportation network.
The impacts of added transportation capacity, however, may be
tempered depending on what kinds of restrictive zoning or growth
management polices are in place. Some suburbs are actually
shrinking because restrictive policies are either pushing new
development farther out on the urban fringe, or even back into the
central city. A result of this is a lack of affordable housing in
older suburbs which are often major employment centers as well.
Trans-
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portation capacity improvements in these areas, th
