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Impacts of Highway Facility Improvements On Travel and Regional Development - Wisconsin TransLinks 21



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MISSION STATEMENT
TRANSLINKS 21-Wisconsin's 21st century transporatation plan-will
outline a comprehensive transportation system that moves people and
goods efficiently,strengthens our economy, protects our environment,
and supports our quality of life.  Working with DOT, the public will
identify Wisconsin's transportation needs-and help to make tomorrow's
transportation choices.  

Tommy G. Thompson, 
Governor 


Charles H. Thompson 
Secretary



           Impacts of Highway Facility Improvements 
                On Travel and Regional Development


                        January 1994

 

ACKNOWLEDGEMENTS


This report was prepared by the Wisconsin Department of
Transportation, Division of Planning and Budget.  The report was
written by Barbara Kipp of the Bureau of Strategic Planning,
Environmental Strategies Section.  Significant input was provided
by the following people: Lynne B. Judd, Chief of the Environmental
Strategies Section; Ken Leonard, Director of the Bureau of
Strategic Planning; Sari Radin and Sarah Dunning of the
Environmental Strategies Section; Joanne Lazarz of the Urban System
Planning Section; Sandra Beaupre, Chief of the Urban Strategies
Section; Lisa Binkley and Sarah Jo Peterson of the Urban Strategies
Section, Dan Yeh, Ron Atkinson and Jane Coffola of the Statewide
System Planning Section; Marlin Beekman of the Division of
Highways, District 6; Tom Batchelor, Deputy Director of the
Division of Highways, District 1; John Hartz, Unit Leader of the
Multi-Modal Planning Unit, Statewide System Planning Section;
Robert McDonald of the Dane County Regional Plan Commission; Ken
Yunker of the Southeast Wisconsin Regional Plan Commission; Ken
Thein of the East Central Wisconsin Regional Plan Commission


 
TABLE OF CONTENTS


Introduction


Chapter 1: Understanding Travel: the Basics . . . . . . . . . . . . . . .3

Travel Growth Trends. . . . . . . . . . . . . . . . . . . . . . . . . . .3

Important Underlying Conditions . . . . . . . . . . . . . . . . . . . . .4

Travel Growth in the Future . . . . . . . . . . . . . . . . . . . . . . .7

Impacts of Growth in Travel and Trip-Making . . . . . . . . . . . . . . .7


Chapter 2: The Role of Service Improvements in Travel Growth. . . . . . .9

Overview of Service Improvement Impacts . . . . . . . . . . . . . . . . .9

Short Term System Impacts . . . . . . . . . . . . . . . . . . . . . . . 10

Long Term Development Impacts . . . . . . . . . . . . . . . . . . . . . 12

What Conclusions Can Be Drawn About the
Impact of Service Improvements? . . . . . . . . . . . . . . . . . . . . 14


Chapter 3: The Role of Travel Forecasting . . . . . . . . . . . . . . . 15

The Policy Environment. . . . . . . . . . . . . . . . . . . . . . . . . 15

Forecasting Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

What Conclusions Can Be Drawn About Travel Forecasting? . . . . . . . . 20


Chapter 4: Policy Options . . . . . . . . . . . . . . . . . . . . . . . 21

  

Introduction

What are the impacts of highway capacity expansion on travel?
How do transportation planning agencies evaluate and respond to
those impacts?

     In recent years, it has been increasingly common for
transportation professionals to be asked these questions as they
consider the merits of making highway facility improvements,
particularly in or near metropolitan areas.  For many areas in the
US, the question became urgent with the passage of the 1990 Clean
Air Act Amendments (CAAA).  The CAAA require that areas currently
not meeting air quality standards for ground-level ozone and carbon
monoxide give explicit consideration to the impact of the
transportation system on air quality.  In addition, the passage of
the Intermodal Surface Transportation Efficiency Act in 1991 has
placed increased emphasis on understanding how the transportation
system interfaces with the natural and built environment.

     Beyond these very specific pieces of legislation, there is a
more generalized concern on the part of environmental interest
groups and public interest groups that the transportation planning
process is not sufficiently sensitive to the environmental impacts
of transportation system improvements on the environment and on
many other aspects of urban life.  WisDOT's interest in this issue
relates to the concern that improved transportation facilities may
quickly become inadequate if the level of travel which occurs on
them is much greater than projected during the planning and design
stages.  The issues of the system's impact on land use, urban form,
and the environment are explored in depth in several other
TRANSLINKS issue papers.  The degree to which the transportation
system, the highway system in particular, contributes to creating
travel demand is explored here.

Growth in levels of traffic have been significant in the last
twenty to thirty years.  It is helpful to break down the factors of
that growth to understand where and how it is occurring.  This
analysis is presented in Chapter One, which includes general
background information about how much travel growth has been
experienced in recent years and some of 


1



the reasons behind the increased levels of travel growth.

     In Chapter Two, the research supporting the effort to
understand the relationship between highway facility improvement
and travel growth is discussed more fully.  Changes in travel
patterns can occur for a variety of reasons after an improvement is
made to a highway facility or when transit services are reduced or
improved.  In the case of highway expansion, there is sometimes a
concern that the improvement will lead to new travel which would
not have occurred if the improvement were not made.  This new
travel, referred to as "induced" travel, is often the focus of
environmental interest groups when the impact of a major highway
improvement is discussed.

     Any effort to analyze when and how highway improvements will
result in increased travel is a complex task, but one that planners
are increasingly being called upon to assess.  Chapter Three
discusses the methods currently used to forecast travel and
discusses current research underway aimed at improving these
methods.
     A well-developed transportation system has long been
acknowledged to be a key element in a healthy economy.  It is
equally clear that historically, transportation facilities have
been significant determinants in the location and form of human
settlements.  As the nature of modem economies changes, the manner
in which transportation facilities impact and shape communities
must be re-examined.  This paper will examine some of the issues
which are key to understanding this relationship, to assist WisDOT
in determining when and how to consider explicitly the impact
transportation facilities will have on overall levels of travel. 
In Chapter Four, several policy options are presented which may
have the potential to improve the way this issue is addressed in
the Department's planning activities.


2

 

Chapter One

Understanding Travel: The Basics

Travel Growth Trends

     In 1990, the Federal Highway Administration (FHWA) conducted a
new comprehensive survey, known as the Nationwide Personal
Transportation Survey (NPTS) to assess the use of the various
transportation modes and to provide information about
characteristics of those traveling and the trips they made.  The
results were compared to surveys conducted previously,
most recently in 1983 (Pisarski, 1992).

     The results showed that between 1983 and 1990, personal miles
traveled (PMT) increased 19% nationwide, a rate of growth that is
considered significant.  Growth in vehicle trip rates (25 %) and
vehicle miles of travel (VMT) (40 %) exceeded the growth in person
trips and miles of travel.  The growth in VMT is most often the
focus of concern (rather than PMT) because of the impacts of
additional vehicles on the transportation system and environmental
impacts, on air quality in particular.

     A look at longer term data from Wisconsin shows similar trends
in travel growth.  Between 1960 and 1990, travel on Wisconsin's
roadways for both personal and commercial activities increased
tremendously.  The data indicate that personal VMT increased by
138% while commercial VMT rose by 401%.

     Examination of the NPTS travel data shows that an increase in
vehicle trip length is the single largest factor of increase, while
an increase in the number of person trips/capita is second largest. 
Another significant contributor is the decrease in vehicle
occupancy (number of persons per vehicle).  Pisarski notes that
vehicle occupancy patterns are important because of what they mean
regarding the efficiency of private vehicle use and their
congestion impacts.  Increases in population and a shift to the
auto from other modes also contributed to the overall increase in
VMT.

     Trends in vehicle occupancy in Wisconsin mirror the national
decrease.  In 1980, less than 62% of all Wisconsin commuters drove
to work alone; by 1990, nearly 75 % of trips to


3



work were made in single-occupancy vehicles (SOVs).  As driving
alone to work became more common, use of other modes -- carpooling,
public transportation, walking, and bicycling all declined. 
Between 1980 and 1990 carpooling, public transportation, and
walking each decreased by over 25 percent as the mode of choice for
travel to work in Wisconsin.

Important Underlying Conditions

     Underlying the increase in travel and these changes in travel
patterns are important shifts in conditions which shape the travel
environment and level of travel demand.  These trends are
independent of the addition of highway capacity.  For example, in
Southeastern Wisconsin, lane mileage on the highway system
increased only 5 % between 1985 and 1992.  An exploration of these
underlying conditions is necessary to assess the likelihood that
these travel trends will continue, and to separate the effects of
these trends from possible induced travel effects due to new
highway capacity.

Economic Trends

     Aggregate levels of highway travel and economic activity are
highly correlated.  Between 1977 and 1983, there was a nationwide
decline in overall trip-making rates which may have been reflective
of the recession in the early eighties.  The increase between 1983
and 1990 may be attributed partially to an increase in economic
well-being.  Higher levels of employment result in more commuters
on the road ana higher personal incomes generally lead to higher
levels of non-work-related trips.  In Wisconsin increases in VMT
correlate with higher income levels.

     Another significant economic variable is the cost of auto
operation.  Although the real cost (adjusted for inflation) of
purchasing an automobiles has risen, the inflation-adjusted cost of
gasoline has declined.  When this declining cost is coupled with
improved per-vehicle fuel economy, the decline in operating costs
has been even more striking.  Once the initial investment has been
made in a vehicle, the declining day-to-day costs of auto operation
have acted as a disincentive for vehicle owners to conserve on
driving.

Demographic/Social Trends

     Although overall increases in population are correlated with
increases in VMT, VMT has

                                     4




historically increased at a substantially faster rate than
population.  Of more significance than total numbers is the age
makeup of the population.  The heaviest driving years are between
the ages of 35 and 54, while teenagers and seniors tend to drive
significantly fewer miles than the average.  Of particular interest
are the effects of the large bulge in the population caused by the
post World War 11 "baby boom".  Because of their sheer numbers, the
entrance of baby boomers into their peak driving years has had an
impact on highway travel demand over the past twenty years. 
However, analysis of the NPTS data shows that the age shift of the
baby boom generation between 1983-90 has begun to result in a
slight decrease in trip-making, as that sector of the population
has begun to move into the higher age groups with typically lower
trip rates.  This suggests that, long term, the growth rate in VMT
is likely to moderate - at least to the extent that it is driven by
the demographic profile of the population.

     Other major factors in determining overall trip rates are the
number and size of households.  Nationwide, the population of 1990
formed 4 million more households than that same population in 1983,
thus resulting in more trips per person.  Women's trip-making rate
increased during the period, a change which seemed to be correlated
with an increase in the proportion of women with driver's licenses,
and the increased share of women employed outside the home. 
National data shows that work trips by women with driver's licenses
are 50% longer than work trips by women without licenses.  Thus, it
appears that overall longer trips lengths are supported by access
to the personal vehicle as a mode of travel.

     It should be noted that demographic changes that affect VMT
may fluctuate from year to year, while longer term trends have a
greater degree of stability and predictability.

Suburbanization

     Throughout the country, one of the most significant factors in
travel growth in the past has been the shift of population from
central cities to suburban and exurban areas throughout the
country.  Older central cities were generally designed at high
densities in a grid pattern that could be served efficiently by
mass transit. In addition, urban areas often contain a variety of
mixed uses, so residents have access on foot to a variety of
employment and retail sites.  In contrast, newly developed suburban
sites are usually of lower density and often separate residences
from other uses.

                               5



   The NPTS data shows that, nationwide, transit's share declined 
more rapidly in suburban areas (where population growth is centered)
than in central cities, probably as a result of several factors,
including the longer transit wait times common in lower-density
areas, and the availability of free parking at suburban work sites. 
The share of walk trips also declined, a trend which is likely to
continue as jobs move to suburban locations (where distances may be
too far for walking).  In general work trip lengths increase with
metropolitan size, in particular for central city residents who
take jobs in the suburbs, or for central city workers who move
their residences to the suburbs.

     Urban and metropolitan areas in Wisconsin have experienced
suburbanization trends similar to the rest of the nation.  For
example, the seven-county southeastern Wisconsin region has seen
significant density changes throughout this century.  In 1920, the
developed areas of the region housed an average of about 18 people
per acre.  As the region developed the density steadily declined --
in 1963 there were nine people per developed acre; in 1970 there
were about eight people per developed acre; and by 1985 there were
fewer than six people per developed acre in the region.  This
decrease in density and increase in distance between homes, work,
and recreation brought with it a decline in the ability to travel
by modes other than the automobile.

     The availability of convenient highway facilities is often
cited as the chief contributor to the shift of jobs and households
away from dense metropolitan areas, but the reality is more
complex.  Many American households prefer to own a single-family
dwelling with private open space.  John Shaw reports research that
generally supports the notion that this is the preferred
residential setting, particularly among families with children
(1993).  Thus, the shift of residences and employment centers to
suburban areas may be a reflection, more than anything else, of the
development community responding to the desires of home buyers. 
Since suburbanization stimulates travel, demand for new highway
capacity frequently follows those trends, to sustain mobility.

     This is not to suggest that desirable communities which can
support travel modes other than the single-occupancy vehicle cannot
be developed.  There is evidence that communities with many of the
characteristics of suburban settings can be supportive of non-SOV
modes.  This issue is discussed in the TRANSLINKS report,
Transportation and Land Use.  Shaw cites the need for additional
research which evaluates whether developments can be designed that
are at

                                     6



densities high enough to support transit, and also meet the
preferences of consumers.


Travel Growth in The Future

     The analyses of several researchers suggests that travel will
not continue to increase in the 1990s as it did in the 1970s and
1980s because several of the forces behind the growth have
moderated - that is, there is not another baby boom generation
entering the peak driving years, the number of women obtaining
drivers licenses and employment will stabilize, and vehicle
occupancy rates (already very low) for work trips cannot continue
to drop indefinitely.  WisDOT estimates that VMT will increase by
34% between 1990 and 2020, reflecting an annual rate of increase of
1.9%, compared to 4.6% annual growth between 1960 and 1990.

     While overall travel growth rates may drop, the growth rates
in individual corridors may continue to rise, thus straining their
capacity.  In 1989, a strategic planning effort known as Metro 2020
was undertaken in Southeastern Wisconsin with the goal of
developing a set of comprehensive, long-range transportation
policies for the region.  One reason for the study was the concern
about the potential for serious congestion problems as a result of
the rate of VMT growth on the Interstate system in the metropolitan
area.  It was determined that as travel growth continues into the
future, portions of the freeway system may experience up to 4-5
hours of congestion during the day.  This pressure on particular
corridors is likely to be experienced in other parts of the state,
particularly in urbanized areas experiencing high rates of
employment and population growth.


The Impacts of Growth In Travel and Trip-making

     The auto has provided tremendous benefits in terms of
convenience and freedom in our society and the high levels of auto
travel in the U.S. are a reflection of the value that Americans
place on access to goods, services and employment.  Yet the
development of any advanced transportation system is inherently
disruptive to the physical environment.  The less desirable effects
of transportation (particularly auto-related) are well-documented
and include: air pollution, water pollution, the oil dependent
state of the U.S., noise, and loss of sensitive natural areas and
agricultural lands.  In addition to exacerbating the existing level
of conditions related to these problems, the significant levels of
growth in VMT quoted above can eventually


                                     7



contribute to a deterioration in the quality of service on some
roadways.  That is, levels of congestion increase, making it more
difficult to travel.  From the standpoint of these many factors,
significant travel growth presents problems.

     In some ways, the large increase in trip-making during the
last decade does seem to represent undesirable trends.  The
decreased efficiency represented by the decrease in vehicle
occupancy for work trips is of concern.  There is some evidence
that central city residents are forced to make long commute trips
that are costly in terms of travel time and/or dollars because of
the movement of jobs away from the central city to the suburbs. 
Often, there is limited availability of housing for low and
moderate income families in these areas (Levine, p. 71).

     In other respects, the increase in travel may represent a
bettering of conditions for certain groups.  The increased mobility
for women and low income groups, giving them the opportunity to
accept jobs which are personally and financially more rewarding, is
surely a positive outcome.

     To the degree that increased trip-making represents an improvement
in the ability of an area's residents to partake in activities that
they value, or live in locations they prefer, it would seem to be
an indicator of an improvement in the quality of life along some
dimensions for the state's residents.  If it results in the loss of
other mode options, or reflects a decline in the accessibility of
employment for some sectors of the population, it may not represent
increased well-being of the community, across the board.

 

                          Chapter Two

          The Role of Service Improvements In Travel Growth

Overview of Service Improvement Impacts

     Basic economic theory suggests that improvement to the
transportation system that reduce the time and costs of travel will
cause people to consume more travel (Brand, 1993, p. 5 1).  This
should not lead to an immediate conclusion that capacity expansion
(or any other type of service improvement) should be viewed as
negative - merely that transportation, as a commodity, is not
exempt from rules that govern the way that all commodities are
purchased and used in market economies.  As noted previously,
improved mobility can represent an improved quality of life on a
variety of dimensions.

     However, the result may also be an overall decrease in system
efficiency, if travel growth is high and travelers shift away from
travel modes or patterns that maximized system efficiency.  Brand
notes why this shift occurs in certain congested corridors:

     The automobile/highway system is a classic example of a system
     characterized by individual choice behavior that puts private
     interests over the public interest.  Every time a person drives a
     car onto a congested roadway, far more aggregate delay is forced 
     on others - on the system - than on the driver.  In economic terms,
     the marginal private cost of highway travel is mu@h less than the
     marginal social cost of travel on the already congested highway
     system. (op.cit, p. 108)

     It is this possibility for a decrease in system efficiency
despite continued investment in transportation facilities that
calls for a careful consideration of the impacts of transportation
improvements prior to system expansion.

     Recent research postulates nine specific, potential effects of
capacity addition:

1.   Route changes
2.   Mode changes
3.   Trip timing changes
4.   Destination changes
5.   Trip frequency/trip chaining changes

                                     9



6.  Auto ownership changes
7.   Residential location changes
8.   Employment location changes
9.   Regional growth changes in either population or employment
(Stopher, 1992; Harvey and Deakin, 1991).

     Peter Stopher notes that the first five of these are likely to
be short to medium term changes, i.e., occurring within the first
two years after a capacity addition opens.  The latter four are
likely to be medium to long term with effects showing up at least
one to two years after the addition is made, and as long as ten
years later.  He believes the short-term changes to be relatively
easy to measure and to attribute to a capacity change, while the
long term changes are more difficult to assess because other events
and conditions over the course of time will have significant
impacts.

     To a large extent, the "induced travel" effects are of most
concern in urbanized areas or their fringes.  Facility expansions
on rural corridors may result in improving a region's access to
other regions in the state or nation.  For example, a significant
highway expansion project may make an entire region more attractive
to businesses which are heavily reliant on having efficient highway
connections to national markets.  This type of effect is generally
considered desirable and not the subject of the discussion to
follow.  Of pertinence here is the issue of when impacts occur that
"use up" the capacity needed to serve long distance travel.  In the
pages ahead, these potential effects will be discussed in more
detail.


Short Term System Impacts

     Travelers choose a travel route based upon a variety of
factors: travel time, perceived safety, scenic amenities,
directness, and road surface quality being the most obvious.  Speed
and the dumber of encumbrances (e.g., stop signals) are often the
primary criteria drivers use (Downs, p.27). When a travel route
(either roadway or transit route) begins to deteriorate along any
of these dimensions, the driver may alter usual travel patterns to
avoid the deteriorating conditions and seek a route that offers
superior service.  Conversely, when a route is improved, travelers
may move to the improved route because it is superior to that
formerly used.  In either case, there is no net change in the
amount of travel.

                                    10



Anthony Downs presents the "Principle of Triple Convergence",
as an explanation for why road expansions made to increase capacity
and relieve congestion problems can sometimes provide only short
term relief.


   As the road's carrying capacity increases, three changes may occur:

1.   Drivers who formerly used alternative routes during peak hours
     switch to the improved facility (route convergence).
2.   Drivers who formerly avoided peak times start traveling during
     these times (time convergence).
3.   Commuters who used to take public transportation switch to
     driving (mode convergence).

     As more drivers converge on the improved facility, traffic
volumes will rise and congested conditions may reappear. Downs
points out that, despite the reappearance of congestion, social
benefits have been realized: parallel routes will be relieved of
some traffic, travel before and after the peak may be faster, and
more people will be able to travel at peak hours which are
presumably more convenient (p.27-28). The impact on public transit
could be negative if transit users decide to switch to driving
because of the improved conditions.  The reality is, however, that
many highway capacity expansions occur in areas where a transit
route does not exist or does not compete well against the auto,
even with congested roadway conditions.  And as De Courla-Souza
points out, "carpools-and buses operating on congested roadways
have no advantage over single occupancy vehicles (1992, p.57)."

     There is some evidence that congestion on major arterials
causes an increase in VMT in that travelers may choose more
circuitous routes to avoid the congestion.  Thus, congestion relief
measures may draw these travelers to the improved facility, and
decrease VMT related to those trips (De Courla-Souza, 1992, p.
157).

     These convergence effects fall into the category of diverted
travel.  Labelling these impacts as short term does not imply that
they are either short-lived or inconsequential.  A careful
evaluation of the purpose of a capacity expansion project relative
to these potential effects may yield a determination that another
solution may be appropriate.  On the other hand, such an analysis
may conclude that either the effects are likely to be minimal, or
that they may be significant but nonetheless the project will
provide overall social benefits.


                                    11



    There is considerable evidence that the scale of diverted
travel may be affected through the use of peak pricing mechanisms,
such as tolls, which can act to deter travelers from shifting their
travel into the peak travel times or onto the toll route (Decourla-
Souza, p. 161).

     The term induced travel is quite distinct from diverted travel
and can be used to refer to trips that were not taken prior to
facility or service improvement.  The improved service may result
in increased travel because the improvement makes a particular trip
more attractive.  Presumably, these are trips that would not have
been made at all (they involved activities that were optional for
the traveler) or involved activities that would have been carried
out in connection with another trip.  This effect is generally
believed to be small, relative to diverted travel effects, and
development-induced impacts, discussed below.


Long-Term Development Travel Impacts

     Induced travel can also result from new development that
occurs as a response to a major facility improvement which brings
about increased accessibility to an area.  The assumption is that
the service improvement is a factor (one of many) that encourages
new development to, occur.  This, in turn, may cause longer trips
to occur, and may result in trips which were formerly taken by
another mode (transit, walking, biking) to be taken by automobile.

     Ryuicha Kitamura suggests that the addition of transportation
capacity may have some significant long-range impacts on household
automobile ownership, residence, and job location choices. 
Improved access to/from fringe areas provided by new or expanded
service may promote the geographic expansion of an urban area, and
eventually result in new levels and patterns of travel in an urban
area (1991).  He believes this development-inducing impact to be
the most important impact, while the changes discussed earlier to
be secondary because they may be small compared to the primary
growth impact.  He points out the difficulty in attempting to
disaggregate the effects of transportation supply, land use,
accessibility, and travel demand, which together form a dynamic and
interrelated system.

     Guiliano (1986) echoes the difficulties in understanding
transportation supply and land use interactions.  She notes that
many highway investments are marginal in terms of accessibility
impacts - i.e., they add some increased accessibility to areas that
already have a high degree of accessibility.  In these cases, a
highway improvement cannot be expected to have much impact

12



on land use.  In areas with limited accessibility, the same project
may have a much greater impact.  She suggests that in these areas
the availability of developable land is a key consideration.  Not
only must there be open land parcels, but there must be an absence
of zoning regulations that would restrict development.  In
addition, the overall state of the regional economy is important. 
An improved facility is not likely to result in a significant level
of new growth in areas where the economy is in decline.


     The impact of the new development on the improved facility may
vary, depending upon what types of land uses appear.  The new
development could be homogeneous in nature, a "bedroom community"
of single-family homes, generating many new trips to employment and
,shopping locations outside of the community.  If zoning
regulations and incentives are in place to promote mixed use
development - employment, retail and residential uses - a new
development center may result.  In. this case, some proportion of
trips generated by the new residents will be made within the new
center, although it is likely that many commute trips will continue
to be made to adjacent communities.

     An important concern is the tendency of local policy-makers to
focus on the immediate benefits to the community of a proposed
development while discounting or ignoring the demands it may place
on state highway facilities.  This problem can be addressed to some
extent by improving coordination between local/regional land use
planning and state-level transportation planning.  The impact of
land use on transportation facilities is covered in the TRANSLINKS
report, Transportation and Land Use: Here, it is sufficient to note
that the impact of improved access on levels of travel is very much
related to the economic and land use regulatory environment in the
area.  In Wisconsin, new development is generally occurring along
existing highway routes in response to changing market forces,
rather than as a result of new capacity.  The development-induced
travel is, in turn, generating demand for new highway capacity.

     Finally, access management on a new or newly expanded regional
facility can affect the level and type of development impacts that
occur in the vicinity of the improved facility.  If the number of
entrances onto a roadway is not controlled, new development may
spring up along the roadway generating many more trips than were
anticipated when the improvement was
designed. In addition, the presence of many intersections on an
improved facility will compromise its safety.  If access is well-
managed along the facility, this type of development

13



is less likely to occur.  A discussion of the importance of access
management in protecting the capacity and efficiency of a highway
corridor is found in the TRANSLINKS report Corridor Preservation
and Access Management Guidance.

     If land use controls are in place along the corridor, new
development may concentrate in more desirable locations, if other
conditions are conducive for growth in the area.  If these
communities have land use regulations in place that promote mixed
uses, and support modes of travel other than the auto, the result
may be a new development center that is more efficient, from a
transportation standpoint.  In this ideal scenario, the function of
the highway facility for intercity travel has been preserved, auto-
oriented patterns of sprawl development have been avoided, and
accommodation has been made for new development.


What Conclusions Can Be Drawn About the Impact of Service
Improvements?


    Under many circumstances, significantly enhanced service
     (whether due to transit service expansion or highway
     improvements) are likely to impact travelers' choices
     regarding travel route, time of travel, mode of travel,
     destination, and trip frequency/trip chaining The degree to
     which any of these effects occurs is dependent upon facility
     conditions existing prior to the improvement, and the
     availability of alternative routes and modes.  In addition,
     the effects in urban areas may be different from the effects
     in rural areas.
    Facility/service changes that greatly improve access to an
     area may have development impacts in the newly-accessed
     region.  The extent, type and location of the development
     impacts will depend on other conditions - in particular, the
     regional economic climate, the land use regulatory
     environment, and the level of access management exercised
     along the facility.
    If an appropriate combination of access management policies
     and land use controls are in place, highway expansion can meet
     the demand for transportation facilities without compromising
     efficiency or safety, and can support desirable regional
     development patterns.  If such controls are not in place,
     highway facility improvements may contribute to auto-oriented
     patterns of development.  The result may be unanticipated
     levels of travel on the improved facility, and a decline in
     the quality of service on the facility from what was expected.

                                    14



                       Chapter Three

                The Role of Travel Forecasting

The Policy Environment
     The methods that are used to forecast future levels of travel
determine whether improved facilities or services are provided, and
when.  Thus, these methods play a pivotal role in the planning
process.  It is important that they predict, with some accuracy,
not only what the level of demand is likely to be before an
improvement is made but also, to the degree possible, what impact
the facility itself will have on demand - i.e., diverted travel
effects, and development related effects.  Two important pieces of
legislation have been enacted in recent years that have placed
increased importance on planning and forecasting processes.


ISTEA   In December of 1991 the federal government adopted the
Intermodal Surface Transportation Efficiency Act (ISTEA).  The
purpose of the act, as described in its statement of policy, is "to
develop a National Intermodal Transportation System that is
economically efficient, environmentally sound, provides the
foundation for the Nation to compete in the global economy and will
move people and goods in an energy efficient manner."

    ISTEA established a requirement for a statewide planning process
that considers the economic, environmental and social effects of
transportation decisions.  It also strengthened the metropolitan
planning process by giving more emphasis to the impacts of
transportation policy decisions on land use and the consistency
between transportation plans and land use plans.

CAAA    In November 1990, President Bush signed the Clean Air Act
Amendments (CAAA) into law.  The CAAA set new requirements in place 
for areas of the country which currently do not meet air quality 
standards. In Wisconsin, there are 11 counties (designated as
nonattainment areas") which violate the standards set for ground-
level ozone, a component of smog.  The law requires the state to 
revise its air quality plan and to submit those revisions to

15



the U.S. Environmental Protection Agency (EPA) for approval.  The
revisions will be prepared in installments over the course of
several years, with the first revisions due in November of
1992.

     The Wisconsin Department of Natural Resources (DNR) is
responsible for submitting the air quality plan revisions to EPA. 
Because motor vehicles are a significant source of air pollution,
the CAAA contain several provisions aimed at controlling pollutants
from motor vehicles.  WISDOT is working closely with DNR on the
transportation-related portions of the air quality plan.

     An important provision in the CAAA is the "Conformity"
requirement, which requires that the level of motor vehicle
emissions forecasted to result from implementation of the
transportation plan in a metropolitan area must be consistent with
the level of motor vehicle emissions forecasted to occur in t@e air
quality plan.  The state must develop a process for carrying out a
Conformity review of the long-range transportation plan and the
shorter-term Transportation Improvements Program (the TIP - a list
of projects scheduled for implementation in the near term) in the
seven-county nonattainment area in Southeast Wisconsin and the
Sheboygan Urbanized area.

     In the short term, implementation of the plan and program must
result in a net reduction in emissions from mobile sources.  In the
long term, implementation will help bring the area into attainment
for ozone standards, and keep pollution below the caps set in the
air quality plan.  This process will not require each project in
the transportation plan and program to be analyzed individually,
rather it requires transportation plans and programs to be analyzed
as a whole.  This analysis is done using the region's travel model,
and the MOBILE model, developed by EPA to estimate the emissions
resulting from the levels of travel projected to occur.  It is also
necessary to develop a process for assessing the air quality
impacts of individual projects which are in rural nonattainment
areas - namely, rural Sheboygan, Manitowoc, Kewaunee and Door
Counties.

     If the plans or projects do not pass the Conformity test,
federally funded transportation projects in those counties cannot
proceed.  State and locally-funded projects will be able to
proceed, but any emissions increases which result from those
projects will have to be offset in other ways, in order for mobile
source emissions to stay below the caps.  States must track

                                    16



actual levels of travel and compare them to the forecasted levels. 
If actual travel is higher than what was forecasted, compensating
measures must be implemented.  As a result of the Conformity and
VMT tracking requirements in the CAAA, the accuracy of
transportation planning and forecasting processes have taken on a
new level of importance.


Forecasting Tools

     There are several ways in which transportation planners
attempt to look into the future, and varying purposes for doing so. 
Following is a brief summary of travel forecasting activities -
their purposes, methodologies and an assessment of their adequacy.

Statewide Forecasts

     WisDOT periodically prepares a statewide highway travel
forecast extending 20+ years into the future.  These forecasts are
based upon an analysis of expected future demographic profiles of
the population and assumptions regarding the number of miles
traveled by various sectors of the population.  The major factors
considered are those discussed earlier in the travel growth trends
section.  The purposes of the forecast are to provide a very
general picture of travel in the future and to assist in developing
forecasts for specific highway projects.  The statewide forecast is
used as a control total for adjustment of the individual project
forecasts. 

Corridor/Segment Forecasts

     WisDOT currently measures traffic volumes at approximately
20,000 locations on the State Trunk Highway (STH) System and on
urban streets.  Traffic counts from each location are usually taken
every three years, and certain seasonal and axle-adjustment factors
are applied.  The result is an Average Annual Daily Traffic (AADT)
volume for that location.  For purposes of carrying out system and
corridor-level planning, the roads on the State Trunk Highway
System are divided into specific segments, with traffic counting
devices placed at both ends of the segment.  In order to develop a
long-range forecast of travel on a particular segment, historical
trends are analyzed using the AADT volumes from the three most
recent counts (three counts, taken over five to six years).  The
trends resulting from the forecast of overall travel in the state
are also considered in determining the shape of the forecast curve. 
An important determinant of the reliability of the forecast for a
particular segment is the degree to which the past history of the
segment is an indicator of future activity levels.  It is also
important that the

17



overall levels of travel are homogeneous throughout the segment. 
If this is not the case, the traffic count data may not accurately
represent what is actually occurring over the entire segment, for
example.

     In addition to the forecasts produced for the system level
analysis, WisDOT conducts a more in-depth analysis before
proceeding with an improvement in non-metropolitan areas.  Here, a
variety of factors may be considered, including specific employment
variables, and projected land developments.
WisDOT's long-range planning process will undergo a change in 1994,
with the development of a new computer model to forecast intercity
levels of travel for passenger and freight vehicles, and predict
modal shares.  The details of how this model will function are not
yet available.

Travel Forecasting In Urbanized Areas

     For many years, the state's urbanized areas have used a
computerized, four-step travel demand model.  Region-specific
inputs reflecting population, employment, households, current and
planned land uses, and the transportation system are entered into
the program.  Travel surveys are conducted to calibrate the model,
to reflect regional travel patterns.  A large percentage of the
state's travel occurs within these urbanized areas, and the travel
model is viewed as a critical tool in understanding the
complexities of the urban travel environment.  Without it, it would
be extremely difficult for transportation planners to predict what
the demands on the system will be in the future, and to make
decisions about responding to that demand.

     The model being used today in Wisconsin's urban areas meets or
exceeds the basic modeling requirements contained in ISTEA and the
CAAA.  However, both ISTEA and the CAAA have put increasing
pressure on the transportation planning community to make
forecasting assessments that are not necessarily within the
capabilities of current modeling practices.

     One area under discussion is whether the modeling process
should better reflect how hospitable the built environment is to
modes of travel other than the automobile.  This would require a
model that could reflect variables such as building setbacks, the
presence of sidewalks, bicycle lanes, etc.  Also of great interest
is developing the capability to model the effects that

                                    18



improved accessibility have on land use development activities, and
the corresponding impacts on levels of travel - discussed in the
previous chapter.  In addition to the potential changes discussed
above, there are other less sweeping changes under consideration to
improve model performance.

     Two major research efforts now underway bear mentioning.  The
Federal Highway Administration (FHWA) has undertaken a Travel Model
Improvement Program.  This is a multiyear effort that has three
tracks - short, intermediate and long-term.  In the short-term
track, efforts are underway to disseminate information on the best
of current practices.  The intermediate track is focusing on
improving how traffic is assigned to particular roadways in the
model.  The long term effort involves more fundamental changes to
the model to improve accuracy, sensitivity, and responsiveness
(Weiner, 1993).

     A second effort is a research project sponsored by 1000
Friends of Oregon, an organization which focuses on growth
management issues.  The study, known as LUTRAQ ("Making the Land
Use, Transportation, Air Quality Connection") is a demonstration
project to develop methodologies for creating and evaluating
alternative land use patterns and design standards that will reduce
dependence on automotive travel, improve mobility for all segments
of society and minimize environmental impacts of the transportation
system.  One important element of the project is an evaluation of
current and new transportation model methodologies.  This
evaluation has concluded that the tools in use today are not
sufficient to meet the new demands being placed upon them. 
Fourteen commercially available models were evaluated, with three
packages selected as potentially the most useful to meet these
demands (Cambridge Systematics, 1991).

     There is one final issue which should be considered when
evaluating the impact of land use changes on the transportation
system is the time frame in which transportation modeling is
conducted, usually 20 years.  Because the scale of an existing
metropolitan area is so large relative to new development, the
travel impacts of new development may appear to be minuscule, and
the benefits of developing a multi-modal travel environment and
system insignificant.  Over a longer time frame (30-40 years),
however, those same impacts and benefits take on more significance.

19



What Conclusions Can Be Drawn About Travel Forecasting?

    Either directly or indirectly, both ISTEA and the CAAA have
     placed a new emphasis on travel forecasting processes.  ISTEA
     requires that the transportation planning process consider the
     impacts of transportation policy on land use, and the CAAA
     require that areas which do not meet air quality standards
     track levels of travel and compensate when actual levels
     exceed forecasted levels.
    Nationally, new computer simulation forecasting methods are
     being explored to improve the ability of planners to
     understand the impact of facility and service improvements in
     metropolitan areas.
    In non-metropolitan areas, Wisconsin has developed a variety
     of techniques for forecasting levels of travel, determining
     the appropriateness of capacity expansion, and evaluating the
     impacts of expansion.  On-going efforts to improve these
     practices should continue.



20


 
Chapter Four
Policy Options

     The transportation planning environment is changing in
response to new federal legislation and increasing concerns about
the impacts of transportation facilities on the natural and built
environment.  Through the TRANSLINKS process, WisDOT hopes to gain
an improved understanding of the critical forces that shape the
transportation system.

     The methods used to assess the need for new facilities in the
future and evaluate the impacts of new or expanded facilities are
at the heart of the evolving transportation planning process. 
Transportation agencies (state and local) are being challenged to
improve their traffic forecasting and evaluation capabilities. 
Several options (not mutually exclusive) for meeting this challenge
are presented here.

1.   Evaluate impacts of a proposed project on the project corridor
     and neighboring communities. 

        This evaluation would be conducted in the system planning 
     process and could contain the following elements:

     a.    Evaluate potential for residential or employment
           increases based on a variety of factors:
           -available work force
           -community plan & existing zoning regulation 
           -existence of water/sewer infrastructure 
           -regional growth trends & economic climate 
           -unique community amenities (e.g., waterfront) 
           -tax climate
           -expected employment opportunities
     b.    Conduct an alternatives' analysis which includes a range
           of potential development

21

        scenarios, based upon the level of improved accessibility
       and the factors listed in a.

     c.    Estimate levels of travel on the improved facility
           associated with the potential development scenarios and
           the resulting environmental impacts.
     d.    Coordinate system plan decisions to link planned land
           uses in a corridor with transportation improvements that
           will serve it efficiently.  This will help assure that
           travel impacts from a transportation investment as
           planned for are acceptable to the community.

2.   Consider methods to incorporate diverted travel impact
     considerations into major project analyses.

           As part of alternatives' analyses, the Department could
conduct stated preference and origin/destination (O/D) surveys on
routes targeted for improvement, parallel corridors, and transit
routes to determine likelihood that facility improvement will
result in diverted travel.  It may also be useful to conduct O/D
travel surveys on recently improved corridors to determine if
diverted travel has occurred as a result of improvement, separating
this impact from other influences in the region.  These efforts may
assist in developing new evaluation techniques to incorporate into
future alternatives analyses.

3.   Develop a research program to evaluate potential improvements
     in modeling and forecasting techniques for urbanized areas.

     A program such as this could contain several elements:

          A state-initiated transportation modelers' network to
           serve as an information exchange forum for state,
           regional and local transportation planners
          Regular review of national research efforts
          Participation in national research and policy-making
           efforts
          Use of experimental model applications in select
           communities or corridors
          Adoption of model improvements supported by sound
           research and theory



22



4.   Develop a plan to systematically improve the segmentation of
     links on rural intercity routes.

     As discussed in Chapter 3, proper segmentation is important
for the development of accurate forecasts on corridors.  The
Department has the ability to easily update segmentation files and
should develop a plan to do so.  Prior to undertaking a capacity
expansion project based upon forecasts of future congestion, the
segmentation for the corridor under discussion should be closely
examined.  This would not apply on Corridors 2020 routes, where
expansion needs have already been extensively analyzed.

5.   Improve coordination between local land use activities and
     state transportation investment activities.

     Local land use controls appear to be a critical variable in
assessing how an expansion of a highway facility will impact a
region's travel patterns.  Improving coordination in this area may
result in more effective use of transportation investment dollars
and have a positive impact on regional development patterns. 
Specific policy alternatives for achieving improved coordination
are discussed in the TRANSLINKS issue paper Transportation and Land
Use.


23



References

Brand, Daniel.  Use of Travel Forecasting Models to Evaluate the
Travel and Environmental Effects of Added Transportation Capacity". 
In Proceedings from Conference "Effects of Added Transportation
Capacity, December 1991; Texas Transportation Institute, College
Station, Texas.

Cambridge Systematics.  "Modeling Practices", Volume I of Making-
the Land Use-Transportation Air Quality Connection, a study
sponsored by 1000 Friends of Oregon.  October 1991.

DeCorla-Souza, Patrick.  "The Transportation-Air Quality
Connection: Perceptions and Reality". ITE 1992 Compendium of
Technical Papers,

Downs, Anthony. Stuck in Traffic. The Brookings Institution,
Washington, D.C., 1992.

Giuliano, Genevieve.  "Land Use Impacts of Transportation
Investments: Highway and Transit" in The Geography of Urban
Transportation, ed.  Susan Hanson.  Guilford Press, 1986: NY, NY.

Harvey, Greg and Deakin, Elizabeth.  "Toward Improved Regional
Transportation Modeling Practice".  Paper presented to the National
Association of Regional Governments Workshop on Transportation
Planning for Air Quality.

Kitamura, Ryuichi.  "Me Effects of Added Transportation Capacity on
Travel: A Review of Theoretical and Empirical Results".. In
Proceedings from Conference "Effects of Added Transportation
Capacity", December 1991; Texas Transportation Institute, College
Station, Texas.

Levine, Jonathan C. "Decentralization of Jobs and Emerging Suburban
Commuting" Transportation Research Record, No. 164, p. 71-80. 
Transportation Research Board, 1992.

Pisarski, Alan E. Travel Behavior Issues in the 90's.  US
Department of Transportation, Federal Highway Administration. 1992

Pisarski, Alan E. "Transportation Investment and Metropolitan
Economic Development: A Reconnaissance of Research Availability and
Requirements".  In Proceedings from Conference 'Effects of Added
Transportation Capacity", December 199 1; Texas Transportation
Institute, College Station, Texas.

Shaw, John.  "Transportation, Land Use and Residential Choice". 
Preprint of paper presented at Transportation Research Board 72
Annual Meeting, January 10-14, 1993, Washington D.C.

Stopher, Peter.  "Travel and Locational Impacts of Added
Transportation Capacity: Experimental Designs.  In Proceedings from
Conference "Effects of Added Transportation Capacity", December
1991; Texas Transportation Institute, College Station, Texas.

Weiner, Ed., "Upgrading U.S. Travel Demand Forecasting
Capabilities" in The Urban Transportation Mo July 9, 1993.



WISCONSIN
TRANSLINKS21




FOR MORE INFORMATION ON THIS TOPIC, CONTACT:

LYNNE B. JUDD
CHIEF, ENVIRONMENTAL STRATEGIES SECTION
WISCONSIN DEPARTMENT OF TRANSPORTATION 
P.O. BOX 7913
MADISON, WI 53707-7913
608/266-7079

FOR ADDITIONAL COPIES, CALL:
OFFICE OF PUBLIC AFFAIRS, 608/266-3581



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