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TRANSIMS Model Design Criteria as Derived from Federal Legislation




Click HERE for graphic.



June 12, 1995                                             LAUR 95-1909


                         TRANSIMS Model Design
                         Criteria as Derived From
                         Federal Legislation

                         Jack Morrison and Verne Loose


                           Executive Summary

TRANSIMS design needs are influenced by assessments by the
professional transportation community that the recent Intermodal
Surface Transportation Act (ISTEA) and Clean Air Act Amendments (CAAA)
generate analytical requirements that exceed the capabilities of
current models and methodologies.  ISTEA defines an integrated state
and metropolitan planning and management system that requires a family
of programmatic, planning, management, and data collection documents
to insure compliance with federal standards.  The CAAA establishes
revised attainment standards for 4 transportation-related pollutants
and their precursors as well as a strengthening of conformity
provisions.  New conformity determination standards will require
transportation planners to prepare long-range demand forecasts and to
conduct air quality modeling with sufficient fidelity to predict
absolute levels of pollution as a function of increased travel demand
as well as changes to the regional transportation system.

TRANSIMS will provide an analytical environment within which state and
local planners can meet these and other analysis requirements.  In
order to be locally adaptable, this environment must incorporate basic
functional representations that can be readily and easily applied to
data characterizing the local environment to form a complete rep-
resentation of the objective region.  To achieve these general
objectives, TRANSIMS
must represent:

   -  the land use and demographic characteristics of different
      regions;
   -  the natural environment associated with that domain;
   -  an multimodal transportation network;
   -  representative populations and commercial environments;
   -  the unique travel decisions of individuals;
   -  detailed vehicle representations;
   -  the detailed dynamics of regional traffic; and
   -  the unique influences of traffic on congestion and air quality.

Key representational requirements are: entity-level representation of
individual travelers and freight items; representation of relatively
sophisticated behavior including choice/utility models; travel and
environmental models, system simulations, and component models that
are sensitive to relatively detailed representations of environmental
and vehicle characteristics; and simulation of continuous traffic,
transit, freight, bike, and pedestrian travel patterns over the course
of an extended period (incorporating both peak and non-peak travel
demand), as well as different days of the week, months, and seasons.

                                                                     1



                           Table of Contents

     1.0   Table of Contents
     3.0   Introduction. . . . . . . . . . . . . . . . . . . . . . . 3
     4.0   High Level Requirements . . . . . . . . . . . . . . . . . 3
           4.1 Motivation. . . . . . . . . . . . . . . . . . . . . . 3
           4.2 System Perspective. . . . . . . . . . . . . . . . . . 4
     5.0   Intermodal Surface Transportation Efficiency Act. . . . . 6
           5.1   Purpose of ISTEA. . . . . . . . . . . . . . . . . . 6
           5.2   Synopsis of the ISTEA . . . . . . . . . . . . . . . 6
              5.2.1 Title I (Surface Transportation) . . . . . . . . 7
              5.2.2 Title II (Highway Safety). . . . . . . . . . . . 8
              5.2.3 Title III (Federal Transit Act Amendments) . . . 8
              5.2.4 Title IV (Motor Carrier Act) . . . . . . . . . . 8
              5.2.5 Title V (Intermodal Transportation). . . . . . . 8
           5.3   Statewide Transportation Planning . . . . . . . . . 8
           5.4   Transportation Improvement Program. . . . . . . . . 9
           5.5   Transportation Plan . . . . . . . . . . . . . . . .10
           5.6   Statewide Transportation Management System. . . . .11
              5.6.1 Introduction . . . . . . . . . . . . . . . . . .11
              5.6.2 State and TMA Congestion Management
                    Systems (CMS). . . . . . . . . . . . . . . . . .12
              5.6.3 State Highway Safety Management System (SMS) . .12
              5.6.4 State Public Transportation Management
                    System (PTMS). . . . . . . . . . . . . . . . . .13
              5.6.5 State Intermodal Management System (IMS) . . . .13
              5.6.6 Traffic Monitoring System (TMS). . . . . . . . .14
     6.0   Clean Air Act Amendment . . . . . . . . . . . . . . . . .15
           6.1   Synopsis of the Clean Air Act Amendments (CAAA).
                    15
              6.1.1 Title I
                    (Attainment and Maintenance of NAAQS). . . . . .15
              6.1.2 Title II
                    (Emissions Standards for Mobile Sources) . . . .16
           6.2   Introduction. . . . . . . . . . . . . . . . . . . .16
           6.3   State Implementation Plan (SIP) . . . . . . . . . .17
           6.4   Conformity Criteria . . . . . . . . . . . . . . . .18
     7.0   Analysis Requirements . . . . . . . . . . . . . . . . . .19
           7.1   Transportation Management Analysis Requirements . .19
              7.1.1 Major Investment Studies . . . . . . . . . . . .19
              7.1.2 Methodology. . . . . . . . . . . . . . . . . . .19
           7.2   Air Quality Analysis Requirements . . . . . . . . .19
              7.2.1 Air Quality Studies. . . . . . . . . . . . . . .19
              7.2.2 Analytical Approach. . . . . . . . . . . . . . .20
              7.2.3 Models . . . . . . . . . . . . . . . . . . . . .20
              7.2.4 Measures of Performance (Sensitivities). . . . .21
     8.0   Derived Functional Requirements for TRANSIMS. . . . . . .22
           8.1 Overview. . . . . . . . . . . . . . . . . . . . . . .22
           8.2 Component Requirements. . . . . . . . . . . . . . . .24
              8.2.1 Transportation System Data Component . . . . . .24
              8.2.2 Transportation Simulation Component. . . . . . .27
     9.0   Definitions, Acronyms, and Abbreviations. . . . . . . . .32
    10.0   References  33

2   TRANSIMS Model Design Criteria as Derived From Federal Legislation



                             Introduction

2.0   Introduction

2.1   Purpose

As the initial step in formalizing the TRANSIMS design, this paper
translates our interpretation of the analytical needs that are
explicitly or implicitly derived from recent federal legislation into
high-level simulation design.  Although some development work has
begun, this document is not a description of TRANSIMS.  Rather, it
communicates the team's understanding of the most likely federal
policy environment within which TRANSIMS will be applied.  This
document, therefore, serves as a basis for feedback from the user
community regarding the overall objectives of the simulation environ-
ment.  It should be noted that the project and design are motivated by
a broad need to enhance the analytical capabilities of the
transportation community and are, therefore, not exclusively
influenced by the recent federal legislation cited in this document.

2.2   Scope

This document is broad in scope to address the entire policy domain
that an integrated simulation framework must embrace.  It is focused
at a level that it can be readily understood by persons who may not be
simulation subject matter experts.

2.3   Audience

This document is directed at metropolitan planning office personnel,
federal and state department of transportation and air quality
personnel, municipal and county planners and other stakeholders in the
air quality and transportation planning communities.  Additional
stakeholders include the environmental community, firms that provide
services to the urban transportation planning community, and the
general public.


3.0   High Level Requirements

3.1   Motivation

TRANSIMS design requirements are significantly influenced by well-
documented assessments by the professional transportation community
that the recent Intermodal Surface Transportation Act (ISTEA) and
Clean Air Act Amendments (CAAA) generate analytical requirements that
exceed the capabilities of models and methodologies currently in use. 
More specifically, state and metropolitan planning organizations will
be required to address forecasting issues related to infrastructure,
congestion, and air quality in more precise and quantitative terms
than have been requited in the past.  Additionally, because of the
legal ramifications of these federally-mandated requirements, the
validity and verification of the embedded models and methodologies
will likely come under greater scrutiny than in the past.

With respect to transportation planning requirements under ISTEA, the
Federal Register [23 CFR Part 500, 2 March -1993] provides this
assessment of state and local professionals as well as national
interest groups.

TRANSIMS Model Design Criteria as Derived From Federal Legislation   3



                        High Level Requirements

[With respect to] the capability of existing transportation planning
models and procedures to identify congestion problems and possible
corrective strategies and to measure performance of implemented
strategies at the micro level.  Approximately one-third of the
responses, generally from rural States, said the existing tools were
adequate.  Another third of the responses, primarily from States with
a mixed level of, urban development, indicated that existing tools
needed to be enhanced.  The remaining responses were from highly
urbanized States and indicated that existing tools were not adequate
and needed to be completely replaced.

A recent analysis of air quality modeling capabilities conducted for
the National Association of Regional Councils provides an equivalent
assessment with respect to CAAA needs.

In order to meet CAA requirements, many metropolitan planning
organizations (MPOs) will need to monitor growth rates, track vehicle
miles of travel, and forecast the impacts of transportation options In
more precise and quantitative terms than have been necessary in the
past- Regardless of whether major updates of regional models and data
bases are deemed necessary, however, many MPOs are finding that the
new planning context calls for new approaches to analysis.
[Specifically].. the typical regional model is unequipped to handle a
plethora of other TCMs, including signal timing, ramp metering, ele-
ments of employer-based demand-management programs, many land use and
urban design measures, and (sometimes) pricing strategies. 2

3.2   System Perspective

Figure 1 represents a top-down view of the policy environment that
TRANSIMS must address.  The figure illustrates how the existing policy
environment for transportation decision-making has been affected by
the recent legislative initiatives represented by ISTEA 1991 and the
CAAA 1990.  The shaded boxes represent the thrust of new legislation
and the new requirements that this legislation imposes on the existing
system and the principal focus of the current TRANSIMS development
program.  We now address the affects of this new legislation.
_________________

   1 Federal Register, Vol. 58, No. 39, 2 March 1993.

   2  Harvey and Deakin, 1992.

4   TRANSIMS Model Design Criteria as Derived From Federal Legislation



                        High Level Requirements

FIGURE 1.   TRANSIMS Policy Environment


Click HERE for graphic.


TRANSIMS Model Design Criteria as Derived From Federal Legislation   5



             Intermodal Surface Transportation Efficiency

4.0   Intermodal Surface Transportation Efficiency Act

4.1   Purpose of ISTEA

Develop a National Intermodal Transportation System that is
economically sound, provides the foundation for the Nation to compete
in the global economy and will move people and goods in an efficient
manner.

The overall objective of the ISTEA is the improved performance of
statewide and metropolitan transportation systems through:

   -  preservation of existing facilities and equipment;

   -  operational enhancements to improve the efficiency and
      environmental impact of the system; and,

   -  capacity enhancements to improve the effectiveness of the
      intermodal system.

The Act defines an integrated, two-tier (state and metropolitan)
planning and management system that requires the preparation,
coordination, approval, and maintenance of a family of programmatic,
planning, management, and data collect documents to insure compliance
with federal standards intended to sustain these objectives.  At both
the state and local level, transportation offices are required to
maintain:

   -  A Transportation Improvement Program CM of prioritized and
      supportable transportation projects for near-term (3-year
      horizon) implementation;

   -  A Transportation Plan that synthesizes local goals and
      objectives with federally mandated criteria into a long-term
      plan (20-year horizon); and,

Associated with these short- and long-range management documents,
states are further required to maintain transportation management
systems that support the three objectives of the Act.  Further, it is
the responsibility of the states and MPOs to insure that
transportation plans in general, and surface transportation plans in
particular, support national air quality goals, guidelines, and
remedial programs as directed under the Clean Air Act Amendment.

4.2   Synopsis of the ISTEA

   1991 ISTEA constitutes a landmark in the definition, resourcing,
and management of the National Highway System (NHS).  This report
focuses on Titles I through VI which address intermodal and surface
transportation.  Titles VII (Air Transportation) and VIII (Extension
of Highway-Related Taxes and Highway Trust Fund) are related only
indirectly to the TRANSIMS project.  Figure 2 highlights those
essential elements of ISTEA that are directly relevant to TRANSIMS.

6   TRANSIMS Model Design Criteria as Derived From Federal Legislation



           Intermodal Surface Transportation Efficiency Act

FIGURE 2.   Relationship Between ISTEA and TRANSIMS


Click HERE for graphic.


4.2.1 Title I (Surface Transportation)

This Title focuses on the activities of the Federal Highways
Administration (FHWA).  Under this Tide, Congress directed that the
four previous federal-aid highway systems (Interstate, Primary,
Secondary and Urban) be redefined as a single National Highway System
(NHS) with a separately defined sub-element, the Interstate System. 
The 155,000 miles of the NHS-defined roadways constitute roughly 15%
of the major roadways in the U.S. Under Title I, Congress apportions
separate funds for the NHS ($211B), the Interstate System ($25B), as
well as a Surface Transportation Program (STP) ($24B) that provides
block grants to the states for both NHS and non-NHS roadways that are
not local or rural minor collectors.  These funding levels are for a
6-year period.

In addition to redefining and resourcing the NHS, Title I of the ISTEA
defines a Congestion Mitigation and Air Quality Improvement Program
($6B) as well as federally mandated procedures for state and
metropolitan transportation program management.  The Congestion
Mitigation and Air Quality section of Title I provides funding for
transportation projects that have air quality benefits.  The federal
management requirements stipulate procedures for the management of
federally supported transportation projects in terms of federal
guidelines for: congestion reduction, safety, public transportation,

TRANSIMS Model Design Criteria as Derived From Federal Legislation   7



           Intermodal Surface Transportation Efficiency Act

intermodalism, pavement and bridge maintenance, and traffic
monitoring.  This program is a particular focus of this report and is
discussed in detail in Section 4.


4.2.2 Title II (Highway Safety)

This Title provides funds ($1.6B) and direction to the FHWA and the
National Highway Traffic Safety Administration (NHTSA) for a national
motor vehicle safety program.  These provisions are not relevant to
TRANSIMS requirements.


4.2.3 Title III (Federal Transit Act Amendments)

This Title renames the Urban Mass Transit Administration the Federal
Transit Administration (FTA) and authorizes $31.5B over 6 years for
Transit Formula and Discretionary programs.  The planning and
management of these transit programs as well as the analysis of
proposed projects under the federally mandated management systems
(Title 1) generate TRANSIMS requirements.


4.2.4 Title IV (Motor Carrier Act)

This Title does not directly affect TRANSIMS requirements.


4.2.5 Title V (Intermodal Transportation)

This Title provides for a new Office of Intermodalism under the Office
of the Secretary of Transportation to coordinate federal research on
intermodal transportation.  Although this Title does not provide
specific requirements for TRANSIMS, it does provide a basis for
support of intermodal management systems for the states as mandated
under Title I.

Although ongoing research programs under Title VI (Research) will not
generate high-level requirements for TRANSIMS, they do identify
potential future system characteristics that may be incorporated into
TRANSIMS design and implementation requirements.  In addition,
TRANSIMS ultimately should provide an analytical environment within
which to support transportation research.


4.3   Statewide Transportation Planning

ISTEA explicitly requires that each state develop and implement a
state planning process to implement this program.  Implicit in this
requirement is the responsibility to develop state-specific goals,
objectives, measures of merit, and procedures to insure that these
programmatic requirements support a coherent, efficient, and effective
intermodal management system.  TRANSIMS is intended to provide an
analytical environment within which state and metropolitan planners
can meet these analytical requirements.

Figure 3 provides a graphical representation of the basic components
of this planning and management system.  The figure reflects the role
of the State Transportation Plan in integrating six federally mandated
management programs (and supporting data collection system) into a
long-range, statewide plan.  Through periodic review and continual
update, these activities provide the basis for the State
Transportation Improvement Program (STIP), that is a resource-
constrained, prioritized list of the proposed, near-term projects to
be supported by federal transportation funds.

Figure 3 also shows that each MPO is required to prepare, coordinate,
and approve its own Transportation Plan and Improvement Program. 
Although Congestion Manage-

8   TRANSIMS Model Design Criteria as Derived From Federal Legislation



           Intermodal Surface Transportation Efficiency Act

ment Plans are required for TMAs, MPOs are not otherwise required to
maintain formal management plans.  However, the majority of the
project-specific and emissions analyses that will provide the bases
for the statewide management systems will be supported at the
metropolitan level.


FIGURE 3.   Integrated State and Metropolitan Transportation Planning
            System


Click HERE for graphic.


4.4   Transportation Improvement Program

The State Transportation Improvement Program (STIP) is a financially
constrained, prioritized list of proposed capital and non-capital
improvement projects along with the agencies responsible for carrying
out each project.  The program is financially constrained by
anticipated state and federal funds.  The planning horizon for the
STIP is not less than 3 years.  The STIP must be updated and submitted
every two years to FHWA and FTA for joint approval.  Each MPO will
prepare a TIP in coordination with state planning authorities who will
provide estimates of available state and federal funds.  Following
approval by the MPO and the governor, the TIP will be included,
without modification, in the STIP.

TRANSIMS Model Design Criteria as Derived From Federal Legislation   9



           Intermodal Surface Transportation Efficiency Act


4.5   Transportation Plan

State and metropolitan transportation plans are continuously updated,
long-range planning documents that integrate federal, state and local
management and planning activities into a comprehensive set of
intermodal plans with the input of 6 federally mandated management
systems as well as TCMs stipulated in the SIP.  The purpose of these
plans is to facilitate the efficient and economic movement of people
and goods in the state.  The required features of all state and
metropolitan plans include:

   -  intermodal planning;
   -  20-year planning horizon;
   -  coordination and integration of state and local plans; and
   -  reference, summarize or contain relevant planning and management
      systems input to planning process.

Unique requirements for the Metropolitan (and TMA) Transportation Plan
are:

   -  review, update and approval by the MPO every:
      -  3 years in nonattainment and maintenance areas, and
      -  5 years in attainment areas;
   -  identification of projected transportation demand of persons and
      goods over the period of the plan;
   -  congestion management strategies including, as appropriate:

      -  traffic operations,
      -  ridesharing,
      -  pedestrian and bicycle facilities,
      -  alternate work schedules,
      -  freight movement options,
      -  high occupancy vehicle treatments,
      -  telecommuting, and
      -  public transportation improvements including: regulatory
         pricing, management, and operations; and
      -  incorporation of a multimodal evaluation of the
         transportation, socioeconomic, environmental, and financial
         impacts of all major investments.

These major transportation investment (subarea and corridor) studies
are required to evaluate the cost-effectiveness and other aspects of
major federally supported problem solutions with respect to local,
state, and national goals and objectives.  These studies will also
provide the analytical basis for demand reduction and operational
management studies conducted in support of congestion management plans
as well as environmental impact studies.  Major investment studies
will analyze the direct and indirect costs of reasonable
transportation alternatives with respect to:

   -  personal mobility improvements;
   -  social, economic, and environmental affects;
   -  safety;

10  TRANSIMS Model Design Criteria as Derived From Federal Legislation



           Intermodal Surface Transportation Efficiency Act

   -  operating efficiencies;
   -  land use and economic development;
   -  financing; and,
   -  environmental impacts and energy consumption.

Within the context of the complex relationship that links
environmental and transportation planning, major investment studies
may provide input to environmental studies.  In that one of the
purpose of TRANSIMS is to provide an analytical environment for these
studies, these serve as high-level design requirements for TRANSIMS.

4.6   Statewide Transportation Management System

4.6.1 Introduction

ISTEA mandates that, prior to 1995, each state implement 6 management
and 1 monitoring system according to the stipulated phase-in schedule
in order to focus transportation programs on the three federally-
mandated objectives:

     -  Objective: Preservation of existing facilities and equipment
           Pavement Management System (PMS)
           Bridge Management System (BMS)
           Public Transportation Management System (PTMS)
           Intermodal Management System (IMS)
     -  Objective: Enhancement of system capacity
           Congestion Management System (CMS), IMS, and PTMS
     -  Objective: Enhancement of operations
           Safety Management System (SMS), IMS, PTMS, and CMS

While not a management system, the Traffic Monitoring System (TMS) is
a federally mandated supporting system that provides for the
collection and management of field data to support analysis of the
traffic aspects of the 6 management systems.  In developing their
overall transportation management system, the state transportation
authorities must coordinate with MPOs and the DOTs Transportation
Research Board.  Directly relevant to TRANS IMS is the requirement for
states to develop and satisfy data requirements to support the 6
management plans as well as to develop measures of performance (MOP)
and measures of effectiveness (MOE) suitable for analyzing the
behavior of the state transportation system relative to the previously
identified objectives.  With respect to data requirements, the state
must identify a family of collectable data that can:

   -  define and monitor the magnitude of system performance
      characteristics;
   -  identify needs;
   -  compare alternative solutions; and
   -  measure implementations (confirm design assumptions).

This paper does not address the PMS, BMS or aspects of the PTMS and
IMS that are strictly associated with preserving existing
infrastructure.  This report focuses on the analysis requirements
associated primarily with CMS, SMS, PTMS, and IMS opera-

TRANSIMS Model Design Criteria as Derived From Federal Legislation  11



           Intermodal Surface Transportation Efficiency Act


tions and capacity as well as the supporting role of the TMS. 
TRANSIMS will support the requirement to analyze the impact of
facility improvement on system capacity.


4.6.2 State and TMA Congestion Management Systems (CMS)

The CMS is a systematic process that provides information on
transportation system performance and alternative strategies to
alleviate congestion and enhance the mobility of persons and goods.  A
CMS includes methods to monitor and evaluate performance, identify
alternative actions, assess and implement cost-effective actions, and
evaluate the effectiveness of implemented actions. [CFR Vol. 58, No.
229, p. 644801

The CMS will consist of. continuing assessment of all transportation
corridors with existing or potential congestion (defined locally); a
data collection and management system for selected performance
measures established cooperatively by the state and affected MPOs,
local officials and subsystem operators; and, a methodology for
evaluating and implementing alternative congestion management
strategies.  Alternative congestion management strategies will
include, but not be limited to:

   -  transportation demand management measures such as car and van-
      pooling, congestion pricing, alternative work hours,
      telecommuting, and parking management;
   -  operational improvements such as intersection and roadway
      widening, addition of general purpose lanes, channelization and
      access management incident management procedures, traffic
      surveillance and control systems, motorist information systems,
      ramp metering, traffic control centers, and computerized signal
      systems;
   -  measures to encourage high occupancy vehicle (HOV) use such as
      HOV lanes, HOV ramp bypass lanes, guaranteed ride home programs,
      and employer trip reduction ordinances;
   -  public transit capital improvements such as exclusive rights-of-
      way (rail and bus), bus bypass ramps, park and ride as well as
      mode change facilities, and paratransit facilities;
   -  public transit operational improvements such as service
      enhancement or expansion, signal preemption, fare reductions,
      and transit information systems;
   -  measures to encourage the use of nontraditional modes such as
      bicycle facilities, pedestrian facilities, and ferry service;
   -  growth management and activity center strategies; and,
   -  intelligent transportation system (ITS) and advanced public
      transportation system technology.

ISTEA mandates that a CMS be incorporated into the planning process
for all TMAs.  When a TMA is classified as nonattainment for ozone
and/or carbon monoxide, a CMS is required for the entire metropolitan
planning area.  These (ozone and CO) nonattainment TMAs must also
provide an analysis of all (multimodal) reasonable travel demand
reduction and operational management strategies for any highway
improvement that will significantly increase SOV capacity.  In
nonattainment or maintenance areas, the CMS will be carefully
coordinated with the SIP as discussed in Section 5.


4.6.3 State Highway Safety Management System (SMS)

The SMS is a systematic process that has the goal of reducing the
number and severity of traffic crashes by ensuring that all
opportunities to improve highway safety are iden-

12  TRANSIMS Model Design Criteria as Derived From Federal Legislation



           Intermodal Surface Transportation Efficiency Act

tified, considered, implemented as appropriate, and evaluated in all
phases of highway planning, design, construction, maintenance, and
operation and by providing information for selecting and implementing
affective highway safety strategies and projects. [CFR Vol. 58, No.
229, p. 63479]

While much of the activity mandated for safety management is beyond
the scope of TRANSIMS, the SMS requires states to collect and maintain
accident, emergency response, and enforcement-related data for
analysis of safety issues and proposed countermeasures.  In addition,
TRANSIMS' explicit treatment of congestion may provide a mechanism for
directly or indirectly relating congestion levels to accident
prediction as well as the contribution of accident response
capabilities to congestion management.


4.6.4 State Public Transportation Management System (PTMS)

The PTMS is a systematic process that collects and analyzes
information on the condition and cost of transit assets on a continual
basis.  It identifies needs as inputs to the metropolitan and
statewide planning process enabling decisionmakers to select cost
effective strategies for providing and maintaining assets in a
serviceable condition.  [CFR, Vol. 58, No. 229, p. 63482]

While maintenance of infrastructure is beyond the scope of TRANSIMS,
ISTEA mandates that proposed PTMS strategies and projects shall be
evaluated for potential inclusion in state and metropolitan
transportation plans and programs especially as they relate to the CMS
and IMS.  Therefore, state transportation authorities must develop
methodologies for analyzing the potential impact of changes in the
characteristics of the public transportation subsystem.  These
subsystem characteristics can include capital and non-capital
improvements that affect capacity and operational capabilities.  In
addition, public transportation vehicles are included in the Traffic
Monitoring System that will, therefore, collect relevant subsystem
performance data.

4.6.5 State Intermodal Management System (IMS)

The IMS is a systematic process of identifying key linkages between
one or more modes of transportation, where the performance or use of
one mode will affect another, defining strategies for improving the
effectiveness of these modal interactions, and evaluation and
implementation of these strategies to enhance the overall system
performance of the transportation system. [CFR Vol. 58, No. 229, p.
63483]

   IMS will consist of: an inventory of intermodal facilities and
systems; a data collection and management system for selected
performance measures; and, a strategy and plan for improving
intermodal efficiency.  ISTEA directs that the states evaluate alter-
native projects with respect to their effect on improving overall
intermodal system efficiency.  Relevant performance measures include:

   -  trip travel time and cost;
   -  volume of cargo and passengers moved (usage);
   -  available facilities (to include parking as well as pedestrian
      and bike facilities);
   -  subsystem and system capacity;
   -  accidents / safety;
   -  ease of access;

TRANSIMS Model Design Criteria as Derived From Federal Legislation  13



           Intermodal Surface Transportation Efficiency Act

   -  mode transfer time, cost, and ease; and,
   -  perceived quality of service.


4.6.6 Traffic Monitoring System (TMS)

The TMS is a systematic process for the collection, analysis, summary,
and retention of highway-related person and vehicular traffic data,
including public transportation on public highways and streets.

The state TMS shall be based on the concepts described in the American
Association of State Highway and Transportation Officials (AASHTO)
"AASHTO Guidelines for Traffic Data Programs," the FHWA "Traffic
Monitoring Guide," and the HPMS Field Manual.  Components of the state
TMS will include: data precision, continuous counter operations, short
term traffic monitoring, and vehicle occupancy monitoring.  For data
precision, the TMS shall meet the standards for statistical precision
established by the FHWA for the HPMS.  With respect to continuous
counter operations, the IMS will provide for estimates of day-of-week,
seasonal, axle correction, growth factors and other components
required to meet the guidelines established by the FHWA.  Short term
traffic monitoring shall be adjusted to reflect annual average
conditions using appropriate adjustment factors.  Vehicle occupancy
data will be collected and maintained on the average number of people
per automobile, light two axle truck, and bus collected through
roadside monitoring, traveler surveys, administrative records,
accident reports, public transportation reports or any other method
approved by the FHWA.

14  TRANSIMS Model Design Criteria as Derived From Federal Legislation



                        Clean Air Act Amendment

5.0   Clean Air Act Amendment

5.1   Synopsis of the Clean Air Act Amendments (CAAA)

Following the Clean Air Act of 1970, emissions of pollutants in
general, and those produced by automobiles in particular, were reduced
in spite of a 24% increase in vehicle miles of travel (VMT) over the
20 year period.  However, by 1988, 101 urban areas continued to exceed
National Ambient Air Quality Standards (NAAQS) for ozone and 44 for
carbon monoxide (CO).  In 1991 Congress passed, and the President
signed, a series of amendments to the CAA.  The first two tides of the
1990 CAAA strengthened the regulatory guidance associated with the
management of air quality standards and established higher standards
for mobile source emissions -- cars and trucks.


5.1.1 Title I (Attainment and Maintenance of NAAQS)

Title I establishes revised attainment standards for 4 transportation-
related pollutants and their precursors:

   -  Ozone (O3);
   -  Carbon Monoxide (CO);
   -  Nitrogen Dioxide;
   -  Particulate Matter of Less Than 10 Microns (PM-10); as well as
   -  Volatile Organic Compounds (VOCs) and Oxides of Nitrogen (NO,)
      in selected cases.

Nonattainment areas are classified according to the extent to which
the standards are exceeded -- from marginal to extreme.  Nonattainment
areas with a more severe status have longer to achieve attainment
status but bear more severe external oversight and have the potential
for more transportation project restrictions.

Title I also strengthens the conformity provisions which ensure that
DOT transportation planners incorporate air quality standards in their
planning.  The 1970 CAA required transportation planners to implement
Transportation Control Measures (TCMs) identified in the State (air
quality) Implementation Plan (SIP) as being necessary to reduce mobile
source emissions in the state and metropolitan plans and programs. 
The 1990 Title I additions now require transportation planners to
determine that all projects, in the aggregate, will not exceed the
emissions levels allocated by the SIP.  Therefore, plans, programs,
and projects must conform to the SIP's purpose to eliminate or reduce
the severity and number of violations of the NAAQS and achieve
expeditious attainment of the these standards.  The complexity and
required fidelity of these analyses will depend on the air quality
status of the nonattainment areas affected.

The new conformity determination standards will further require
transportation planners to prepare long-range transportation demand
forecasts and to conduct air quality modeling with sufficient fidelity
to predict absolute levels of pollution as a function of increased
travel demand as well as changes in the design and operation of the
regional transportation system.  The unprecedented scope of this
analytical requirement (regional transportation system performance
sensitivity to detailed emissions models) motivated the TRANSIMS
project and its specific design requirements.

TRANSIMS Model Design Criteria as Derived From Federal Legislation  15



                        Clean Air Act Amendment

5.1.2 Title II (Emissions Standards for Mobile Sources)

This Title establishes more stringent emissions standards for cars and
trucks produced between 1996 and 2003.  With respect to TRANSIMS, this
regulation generates a requirement to incorporate emissions models
that are sensitive to engineering design features of cars and trucks. 
The clean fuels portion of this Title generates an additional modeling
requirement sensitivity to alternative fuel sources in a percentage of
the modeled vehicles.

5.2   Introduction

While the CAAA of 1990 established a number of specific performance
standards for nonattainment areas as well as mobile sources, the focus
of this document is the analytical procedures associated with
supporting the development of TCMs as well as making conformity
determinations for transportation projects, plans, and programs as
defined under the ISTEA.

The air quality regulatory environment is as reflected in Figure 4.
TCMs are specific transportation-related projects (capital or
operational) associated with achieving required reductions in
transportation-related pollutants.  When incorporated into the SIP,
these TCMs are required to be included and supported in the
appropriate state and metropolitan TIN and Plans.  Conformity
Determinations, conducted and validated by the MPO or State DOT,
verify that the TCMs are being implemented, and that all other
transportation projects have been evaluated, in the aggregate, to
insure that the overall program-

FIGURE 4.   Conformity Determination


Click HERE for graphic.


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                        Clean Air Act Amendment

5.3   State Implementation Plan (SIP)

Figure 5 reflects the general process by which each state develops the
transportation-related input to the SIP.  The principal components of
this process are: National Ambient Air Quality Standards; projections
of regional growth; an emissions analysis; projections of specific
pollutants across an emissions budget and milestone and attainment
dates; and TCMs and other measures as required to insure future
regional transportation conditions are constrained to remain within
the prescribed emissions budget.


FIGURE 5.   SIP Development Process


Click HERE for graphic.


TRANSIMS Model Design Criteria as Derived From Federal Legislation  17



                        Clean Air Act Amendment

The NAAQS are national, source-independent thresholds of pollutant
concentrations in the atmosphere.  The emissions budget is an
allocation of maximum allowable pollutant quantity to the various
emissions sources in a nonattainment or maintenance area so that
overall pollution levels remain within, or are reduced over time, to
EPA standards (NAAQS).  Because each nonattainment or maintenance area
has different natural and man-made environmental dynamics and social
goals, the emissions budget provides for a regionally specialized
formula for achieving national air quality standards.  One of the
primary purposes of the SIP is to develop a rationale for this
regional formula.


5.4   Conformity Criteria

A Conformity Determination is required for all metropolitan plans and
TIPS.  For some federally-funded improvements, project-level
conformity tests are also required. in addition, regionally-
significant non-federal projects must come from a conforming plan and
a conforming TIP or be included in the conformity analyses before they
proceed.  TCMs are not exempt from the conformity requirements. 
Further, conforming projects that have a significant change in design
concept and scope from that in the conformity analyses, must be
recycled through the conformity process.  Conformity determinations
will be updated no less frequently than every three years as well as
within 18 months of EPA approval of a new SIP that modifies previous
emissions budgets or TCMs.

The MPO and U.S. DOT (FHWA and FTA) will make the conformity
determination for metropolitan plans and TIPs, the State DOT and U.S.
DOT are responsible for conformity determination in rural
nonattainment areas, and project sponsors and U.S. DOT are responsible
for project-level determinations.  All are done in consultation with
EPA and state and local air quality agencies according to procedures
established in the transportation conformity rule and the State's
conformity SIP revision.

However, all Conformity Determinations will be based on EPA/DOT
prescribed criteria summarized as follows:

   -  based on latest planning assumptions and forecasts;
   -  based on latest EPA-approved emissions models;
   -  based on consultation with air quality agencies;
   -  provides for timely implementation of TCMs;
   -  demonstrates consistency with emissions budgets in the SIP;
   -  based on regional emissions analysis in nonattainment and
      maintenance areas;
   -  in CO nonattainment areas, eliminates or reduces severity of
      localized CO violations (hot spots);
   -  doesn't create hot spots;
   -  in ozone and CO nonattainment areas, contributes to reductions
      of ozone and CO emissions; and,
   -  in PM10 and NO2 nonattainment areas, contribute to reductions or
      not increase PM10 or NO2 respectively.

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                         Analysis Requirements

6.0   Analysis Requirements

6.1   Transportation Management Analysis Requirements

6.1.1 Major Investment Studies

Responding to a previous tendency to fail to fully consider a wide
range of intermodal options when responding to perceived
transportation system requirements, planning regulations include
provisions that address the management of major transportation
investment studies.  These provisions are intended to insure a broadly
coordinated effort that provides a wide range of feasible alternatives
for consideration.  A major metropolitan transportation investment is
generally defined as a problem that would require a solution
equivalent to a controlled access arterial of more than a mile or
transit projects of a similar scale.

Either within, or in association with, major investment studies,
transportation planners also will be required to conduct environmental
analyses for input to environmental impact statements as well as
emissions analyses to support conformity determinations for both
metropolitan and rural nonattainment areas.  Specific EPA/FHWA/FTA
requirements associated with air quality studies are addressed
injection 6.2 below.

Finally, major investment studies will, when appropriate. serve as the
supporting analysis of demand reduction and operational management
strategies required for Congestion Management Systems.

6.1.2 Methodology

Major investment studies should evaluate the effectiveness and cost-
effectiveness of alternative transportation investments or strategies
in satisfying local, state and federal goals and objectives.  The
analysis should consider the direct and indirect costs and reasonable
alternatives with respect to: personal mobility improvement; social,
economic, and environmental effects; safety; operating efficiency;
land use and economic development; financing and energy consumption.

6.2   Air Quality Analysis Requirements

6.2.1 Air Quality Studies

CAAA requires that conformity determinations be made on all TIPs and
FHWA and FTA funded or approved projects in both metropolitan and
rural nonattainment and maintenance areas.  Any such transportation
project not included in a conforming program or plan must be part of a
regional analysis that includes all projects in the plan and TIP and
the project itself.  In nonattainment and maintenance areas, this
determination must be based on an emissions analysis.  EPA defines
regionally significant to mean a facility with a principal arterial or
higher functional classification as well as any facility that serves
inter-regional travel needs, serves major activity centers in the
region, or supports major transportation terminals in the region.

In areas that are nonattainment or maintenance areas for PM10 and CO,
Hot Spot analyses are required for sites (intersections) that are
current or potential sources of local-

TRANSIMS Model Design Criteria as Derived From Federal Legislation  19



                         Analysis Requirements

ized pollution -- typically, congestion-based.  Hot Spot analysis is
not required for temporary, construction-related increases in
emissions.

6.2.2 Analytical Approach

Emissions analyses will be based on comparison of transportation-
related emissions levels, in each of a series of "snapshot" analysis
years between a Baseline and Action Scenario and/or to the emissions
budgets allocated for the transportation system component (traffic,
transit, etc.). In each analysis year, a Baseline Scenario will be
analyzed.  This scenario, or alternative, will consist of:

   -  all existing, regionally significant highway/transit facilities,
      services, and activities;

   -  all on-going travel demand management or transportation system
      management activities; and,

   -  all regionally significant projects under construction or
      undergoing right-of-way acquisition from the first 3 years of
      the previously conforming plan and/or TIP or those that have
      completed the NEPA process.

One or more Action Scenarios also will be analyzed.  Action Scenarios
will consist of:

   -  all facilities, services and activities in the Baseline
      Scenario;

   -  all approved TCMs and regionally significant projects in the
      transportation plan that will be operational or in effect in the
      analysis year;

   -  all travel demand management programs and transportation system
      management activities known to the MPO that also have been
      adopted, modified, or funded; and

   -  all other expected, regionally significant projects, activities,
      or services.

Emissions and concentration for each of the relevant pollutants and
scenarios (by analysis year) will be predicted.  This prediction will
be based on forecasted changes in population, land use, and commercial
activity for the year under analysis.  This forecast also will include
projections of background emissions for each pollutant from sources
other than those explicitly modeled.  The ambient temperature assumed
in the analysis shall be consistent with those used to compute the
emissions budgets in the SIP.  Criteria for success is met if. one,
the predicted regional emissions for the Action Scenario(s) are less
than those predicted for the Baseline Scenario; two, they can be
expected to remain so for any intervening period between milestone
years; and three, they remain less than those levels allocated in the
SIP.

6.2.3 Models

Federal rule-making has established that the latest approved version
of the MOBIL motor vehicle emissions model is the required emissions
model for emissions analysis, hot spot analysis, and conformity
determinations outside of the state of California. Within California,
EMFAC is the approved motor vehicle emissions model for air quality
analyses conducted under the CAAA.  However, transportation planners
remain unsatisfied with the predictive capabilities of these models. 
Addressing these limitations, is believed to be a functional
requirement that will be discussed in Section 6.

While federal regulations do not prescribe a specific transportation
model, they do prescribe features that are required for CO and ozone
areas as classified as serious and above.  These required features
include:

20  TRANSIMS Model Design Criteria as Derived From Federal Legislation



                         Analysis Requirements

   -  a network-based transportation model that relates travel demand
      and system performance to best available data for land use
      patterns, population demographics, employment transportation
      infrastructure and transportation policies;

   -  sensitivity to ambient temperature;

   -  representations that are in accordance with acceptable
      professional practice, and reasonable for purposes of emission
      estimation;

   -  validation within the last 10 years against vehicle ground
      counts;

   -  capacity-sensitive traffic assignment methodology;

   -  link assignment times must be in agreement with zone-to-zone
      travel times;

   -  free-flow speeds on network links must be based on empirical
      observations;

   -  traffic speeds and delays must also be sensitive to traffic
      volume;

   -  peak and off-peak travel requirements and travel times must be
      provided;

   -  trip generation, trip distribution and mode choice must be
      sensitive to pricing;

   -  documented correspondence between the assumed land-use scenario
      and the future transportation system being represented;

   -  a trip-generation dependency on the accessibility of
      destinations via the transportation network is strongly
      encouraged;

   -  a dependency between regional economic and population growth on
      the accessibility of destinations is also strongly encouraged.

In addition, Highway Performance Monitoring System (HPMS) estimates of
vehicle miles traveled (VMT) shall be considered the standard for this
principal MOP except where and when EPA and FHWA determine that HPMS
is inappropriate.  When model estimates are different from the HPMS
data, appropriate methods will be applied to calibrate the model
results to the HPMS estimates for the same period.

6.2.4 Measures of Performance (Sensitivities)

   -  Vehicle Miles Traveled (VMT)
   -  Speed
   -  Acceleration
   -  Vehicle and Engine Characteristics
   -  Fuel
   -  Startup (Hot vs.  Cold Start)
   -  Idling
   -  the effect of trip frequency on evaporative emissions

TRANSIMS Model Design Criteria as Derived From Federal Legislation  21



             Derived Functional Requirements for TRANSIMS

7.0   Derived Functional Requirements for TRANSIMS

7.1   Overview

The purpose of TRANSIMS is to provide an analytical environment within
which state and local transportation planners can meet the
programmatic requirements that have been previously discussed.  To
meet this requirement, this environment must be adaptable to the
unique requirements of each local planner.  This is accomplished by
maintaining a core of fundamental functional representations that can
be readily and easily applied to data characterizing the local
environment, as well as proposed and forecasted changes, to form a
complete representation of the objective region.  However, to meet the
evolving requirements for more quantitative and accurate analysis,
TRANSIMS also must incorporate a greater level of detail than is found
in current regional planning models that are applied to land use and
regional economic development.  To achieve these objectives, TRANSIMS
must represent:

   -  the land use and demographic characteristics of different
      regional transportation domains;
   -  the natural environment associated with that domain to include
      topography, meteorology, and background levels of pollution;
   -  an intermodal transportation network down-to and including minor
      arterials, along with all potential nodes;
   -  representative populations and commercial environments based
      upon survey data for households, commercial and industrial
      entities;
   -  the unique travel decisions (time-of-day, origin/destination,
      route, mode, etc.) of individuals based on a wide range of
      socioeconomic characteristics;
   -  automobile and commercial transportation systems in sufficient
      detail to incorporate the air quality emission effects of
      different engine and fuel characteristics;
   -  the detailed (micro) and dynamic aspects of traffic in a region
      of interest including congestion, signals, incident detection,
      and driver behavior;
   -  the unique influences of traffic on congestion and air quality;
      and
   -  provide user-friendly analytical support capabilities.

In addition to these requirements, an entity-level simulation will be
required for three reasons:

   -  first, traffic studies will continue to require representations
      of detailed characteristics of travelers, vehicles and the
      transportation system components themselves;
   -  second, model validation will require comparison of simulation
      output to traffic counts and other survey data that is collected
      at the entity level; and,
   -  third, for theoretical reasons related to the ability of
      inaccurate aggregated models to generate false support for
      themselves, entity-level representations will insure that
      system-level behavior is. derived explicitly from valid entity-
      level representations.

Figure 6 presents a diagram of the TRANSIMS, high-level, functional
requirements in terms of the policy environment portrayed in Figure 1.

22  TRANSIMS Model Design Criteria as Derived From Federal Legislation



             Derived Functional Requirements for TRANSIMS

FIGURE 6.   TRANSIMS Modeling and Analysis Environment


Click HERE for graphic.


TRANSIMS Model Design Criteria as Derived From Federal Legislation  23



             Derived Functional Requirements for TRANSIMS

7.2   Component Requirements

The analytical environment consists of- a complex representation of
the transportation domain that characterizes a region; a domain-
independent transportation simulation/ model; and, a set of supporting
programs and facilities to translate simulation histories into
statistics that can be used to make decisions with respect to public
transportation and air quality goals and objectives.  Key
representational requirements are:

   -  entity-level representation of individual travelers and freight
      items;
   -  data bases and simulations that support the representation of
      relatively sophisticated behavior as well as choice/utility
      models that are sensitive to travel time constraints,
      preferences, travel behavior, cost, and perceived quality of
      service;
   -  travel and environmental models, system simulations, and
      component models that are sensitive to relatively detailed
      representations of environmental and vehicle characteristics
      correlated to both the geographic and demographic distribution
      of travelers; and
   -  simulation of continuous traffic, transit, freight, bike, and
      pedestrian travel over the course of extended period
      (incorporate both peak and non-peak travel requirements)
      different days of the week, months, and seasons etc.

7.2.1 Transportation System Data Component (Statistical Models, Data
      Structures, and Data Bases that Characterize a Transportation
      Region)

Travel behavior is strongly influenced by the unique transportation
requirements associated with different populations as well as their
spatial and temporal relationships to commercial, government,
entertainment and other public and private facilities.  To simulate
realistic transportation demand, TRANSIMS will require both
statistical models and data to represent these populations,
activities, and environments.  The analytical environment must also
accurately represent both current and future transportation infra-
structure, facilities, services and operational characteristics. 
Finally, the simulation environment must represent those aspects of
the natural environment that influence air quality.  These
representational requirements necessitate four basic data sources and
information as indicated in Figure 6.

Land Use.  Patterns of land use as well as the demographics of the
population generate transportation requirements and patterns of
vehicle use that affect, for example, air quality.  TRANSIMS will
require representations of geographic clusters in terms of their
population, residential, commercial activities and terrain referenced
to geographic coordinates.  These representations will provide the
basis for spatially referencing populations, residential, and
commercial activities.  They will also provide the basis for linking
traveler characteristics, origins, and destinations in trips and trip
chains as well as for characterizing the ground as it relates to
vehicle performance and emissions.  Moreover, they provide the
structural basis for forecasting.

To represent the evolution of the region in time, TRANSIMS must employ
techniques to modify land use and demographic representations based on
input from external sources.  Because of the poorly understood cause
and effect relationships between infrastructure policy and subsequent
patterns of growth, the TRANSIMS analytical methodology should
naturally support forecasting methods.  Although the TRANSIMS project
is not specifically funded to satisfy this requirement, its
relationship to this problem is obvious.

24  TRANSIMS Model Design Criteria as Derived From Federal Legislation



             Derived Functional Requirements for TRANSIMS,

General representational requirements identified in our policy
research include

   -  the land use and demographic characteristics of different
      regional transportation domains are required, along with
   -  the environment associated with those domains to include
      topography (including urban terrain), meteorology, and
      background levels of pollution from static. nonmobile sources,
      and a
   -  methodology that explicitly relates any future transportation
      system being represented to the associated land-use scenario.

Traveling Population.  The purpose of the representative populations
is to produce realistic travel requirements for the intermodal system
and also to generate appropriate distributions for the behavioral
models of travelers.  To support this requirement, the TRANSIMS
project must provide suitable population, residential and commercial
data bases.  It must also provide the methodologies and environment Co
ascertain the variables that most effectively discriminate travel
demand and behavior for given problems.

Driving, as well as biking and walking, behavior is sensitive to the
demographic characteristics of drivers and has a significant effect on
fuel consumption, emissions, accidents, and incidents of congestion. 
For this reason, TRANSIMS must incorporate the demographic
characteristics of each individual driver as well as methods for
mapping these characteristics to the dynamic aspects of driver
behavior and their affects on driver-system, driver-driver, and
driver-vehicle interactions.

Vehicle characteristics also influence fuel consumption and emissions. 
For TRANSIMS to faithfully represent the air quality impacts of
different populations and transportation systems, it must incorporate
representations of vehicles that are sensitive to the relationships
between driver behavior, engine characteristics, fuel type, vehicle
performance, and emissions.

TRANSIMS must be capable of generating representative disaggregate
populations from aggregate statistical data about the social, economic
and demographic characteristics of the region.  Extending available
census and, survey data to disaggregate populations that accurately
discriminate the unique transportation requirements of different
demographic population profiles is a research requirement for
TRANSIMS.

General representational requirements identified in our policy
research include:

   -  aggregated populations and commercial demographics as well as
      commercial activity profiles (hours of operation etc.) to
      support the generation of
   -  disaggregated traveler populations to drive the transportation
      simulation; as well as
   -  automobile and commercial transportation systems in sufficient
      detail to incorporate the air quality emission effects of
      different engine and fuel characteristics.

Atmosphere.  Meteorological conditions exert a significant influence
on air quality.  These conditions include seasonal temperatures and
humidity, background air quality from non-mobile sources, prevailing
winds, and the influence of large natural features such as mountains
and oceans on air movement patterns.  Although these phenomena are
relatively well understood, developing an appropriately scaled,
regional air quality model that can efficiently and accurately
translate explicit representation of individual

TRANSIMS Model Design Criteria as Derived From Federal Legislation  25



             Derived Functional Requirements for TRANSIMS


vehicle emissions into a dynamic representation of air quality for a
region or major air basin may present a significant computational
challenge for TRANSIMS.  Determining the levels of fidelity and
aggregation that satisfy these criteria remains an unresolved
analytical requirement for TRANSIMS.

General representational requirements identified in our policy
research include the natural environment associated with a
transportation region to include topography, meteorology, and
background levels of pollution.

Intermodal Transportation System.  The transportation system includes
a set of mode-specific links and nodes that characterize the
transportation constraints on vehicles and travelers.  To support
transportation system design and air quality studies effectively,
TRANSIMS must represent the influence of all current and anticipated
transportation facilities, technologies and operational procedures on
traveler and vehicle behavior at both the micro-(individual) and macro
(system) level.  Specifically, the network must include all
interstate, freeway, expressway, as well as other principal and minor
arterials and possibly major collectors.  It must also include any
unique transit links as well as unique links for pedestrian and
bicycle traffic.  While near-term TRANSIMS design will not include an
explicit representation of air, rail and waterborne transport, the
network must include the intermodal transfer of travelers and freight
to-and-from surface facilities to these carriers.  To minimize the
computational burden associated with simulating travel, development of
efficient data structures for roadways and pathways will be an
important design issue for TRANSIMS.

Traffic nodes represent the intersection of more than one link, mode
of travel, or fink class such as would occur in transitioning from a
public access highway to a toll road.  Traffic nodes typically
incorporate some method of vehicle control (signals) as well as route
selection (function of congestion and pricing) and, occasionally, mode
transfer.  Transportation nodes influence overall traffic flow as well
as the air quality implications from congestion.  Because of
anticipated reductions in the rate of growth of new roadways, many of
the new transportation system improvements are expected to focus on
improved design and management of transportation nodes to maximize
overall system capacity by efficiently distributing peak demand across
the system.  The increasing sophistication of automated traffic
control technologies and the uncertainties associated with driver
behavior (choice and utility), effective representation of modern
traffic nodes will present a challenge to TRANSIMS design.

Intermodal nodes are important features of a number of demand
reduction proposals and TCMs.  Important features of these nodes
include parking and freight transfer facilities, as well as mode
transfer characteristics that affect travel -time, cost and traveler
preferences for both passengers and freight.

General representational requirements identified in our policy
research include an intermodal transportation network down-to and
including minor arterials and pathways, along with detailed
characterization of all potential nodes.

Specific representational requirements identified in our policy
research include representation of:

26  TRANSIMS Model Design Criteria as Derived From Federal Legislation




             Derived Functional Requirements for TRANSIMS


   -  general system characteristics to include lane miles,
      intersection and roadway width and lanes, roadway grade,
      parking, freight, and mode transfer facilities, HOV lane miles,
      node characteristics, roadway functional class, and type and
      location of construction;

   -  operational characteristics such as channelization, traffic
      surveillance and control systems, motorist information systems,
      ramp metering, traffic control centers, and standard as well as
      computerized signal systems;

   -  measures to encourage high occupancy vehicle (HOV) use such as
      HOV lanes,

   -  HOV ramp bypass lanes, guaranteed ride home programs, and
      employer trip reduction ordinances;

   -  public transit capital improvements such as exclusive rights-of-
      way (rail and bus), bus bypass ramps, park and ride as well as
      mode change facilities, and paratransit facilities;

   -  public transit operational improvements such as service
      enhancement or expansion, signal preemption and transit
      information systems;

   -  explicit travel cost data to include tolls and congestion
      pricing management systems;

   -  intelligent vehicle highway system (IVHS) and advanced public
      transportation system technology.

7.2.2 Transportation Simulation Component

The transportation simulation consists of four activities:

   -  generate realistic transportation requirements for the system as
      a whole while providing feedback;

   -  exercise the transportation system;

   -  apply vehicle travel histories to produce selected emissions and
      their resulting influence on the atmosphere; and,

   -  provide appropriate travel histories in statistical form for
      analysis by transportation and air quality planners.

Household and Commercial Activity Disaggregation Component.  From an
understanding of the size and demographic features of the regional
population (aggregated population discussed above) and spatial and
characteristic distribution of commercial and other activities (Land
Use data discussed above), the disaggregation component produces a
complete set of travel requirements for each population cluster. 
Specifically, the component should generate, for each household in
each population cluster, a set of required travel activities
characterized by travelers, origin, destination, time constraint, and
purpose.  The component should further clusters these activities into
trip chains according to spatial and temporal constraints.  Travel
requirements are, therefore, represented as a set of trip chains
characterized by a set of origin destination pairs with associated
time constraints, as well as a driver and passengers.  By inheritance,
these trips can be further characterized by the driver's demographic
characteristics, vehicle type and driver pattern of behavior and
preferences.


The Disaggregation Component should produce a travel requirements data
base that accurately reflects the number and distribution of travel
requirements that the true regional population would produce during
the period being simulated.  Although no

TRANSIMS Model Design Criteria as Derived From Federal Legislation  27



             Derived Functional Requirements for TRANSIMS

individual trip need be linked to a predictable event by the true
population, the resulting distribution of trips should reflect, in
space and time, representative regional transportation requirements.

Because of the limitations of existing data and statistical
techniques, development of a Disaggregation Component is a significant
research requirement for TRANSIMS.

General representational requirements identified in our policy
research include:

   -  a trip-generation dependency on the accessibility of
      destinations via the transportation network;

   -  a network-based transportation component that relates travel
      requirements and system performance to best available data for
      land use patterns, population demographics, employment,
      transportation infrastructure and transportation policies;

   -  treatment of the unique travel decisions (time-of-day,
      origin/destination, route, mode, etc.) of individuals based on
      the wide range of socio-economic characteristics that influence
      personal travel decisions; and

   -  treatment of adopted congestion management alternatives
      including alternate work schedules.

Trip/Travel Planner.  The Travel/Intermodal Route Planner should
convert the trip requirements from the Disaggregation Component into
intermodal travel plans based on the space and time constraints of the
trip, demographically-defined traveler preferences, and transportation
system characteristics.  Through one or more optimization techniques,
this component should select model-routes choices that optimize the
travelers transportation utility function subject to the constraints
imposed by the trip and transportation system constraints.  Because of
the interrelationship between travel requirements and planning,
previous modeling experience has indicated that equilibrium methods
are required to ensure that realistically efficient travel
requirements are generated.  In Figure 6, these methods are
represented, for between-model equilibration, as a feedback loop.

Because of the complexity associated with this optimization task, as
well as the unique ability of humans to do this effectively, realistic
mode/route assignment for large, complex populations is a research
requirement for TRANSIMS.

General representational requirements identified in our policy re-
search include:

-  trip distribution and mode choice must be sensitive to pricing;

-  traffic assignment methodology must be sensitive to capacity; and

-  link assignment times must be in agreement with zone-to-zone travel
   times;

Specific representational requirements identified in our policy
research include representation of:

   -  congestion management alternatives including: ridesharing (car
      and van pools); walking or biking; parking management; freight
      movement options; telecommuting;  and public transportation.


   -  trip travel time and cost;

28  TRANSIMS Model Design Criteria as Derived From Federal Legislation



             Derived Functional Requirements for TRANSIMS


   -  volume of cargo and passengers moved (usage);

   -  available facilities (potential origins and destination
      choices);

   -  subsystem and system capacity;

   -  accidents / safety;

   -  ease of access;

   -  mode transfer time, cost, and ease; and,

   -  perceived quality of service.

Travel Network Simulation.  The centerpiece of the TRANSIMS
environment is the simulation that results from applying, to the
regional transportation data base, the transportation plans produced
by the Planner as well as the Land Use (ground surface charac-
teristics), Population (driver behavior), and Intermodal
Transportation System data.  However, a unique challenge for TRANSIMS
results from ISTEA and CAAAs implicit requirement to integrate, into a
single simulation, the analytical requirements that were previously
satisfied by two classes of models -- detailed traffic and air quality
simulations and more aggregated regional planning and forecasting
models.  Therefore, the TRANSIMS traffic simulation is required to
satisfy the detailed representational requirements of previous traffic
simulations within an environment that includes a large metropolitan
area over an extended time period.  The computations that can be
expected to result from this integration generate a research
requirement to investigate new and more efficient simulation methods.

The required functionality of the simulation includes the ability to
represent and record, at both the entity (vehicle/driver) and system
level, the results of the interactions occur between the driver and
other drivers (passing and accidents), the driver and the
transportation system (signals and congestion), and the driver's
vehicle and the environment (engine performance and emissions).  The
magnitude of the simulated environment along with some of the unique
features of congestion generate a number of research, design, and
analysis issues related to determining the minimal representational
levels necessary to provide accurate characterizations of these
interactions.  The term minimal representational levels applies to
both input data sets and resulting simulation output (histories).

General representational requirements identified in our policy
research include:

   -  free-flow speeds on network links must be based on empirical
      observations;

   -  traffic speeds and delays must also be sensitive to traffic
      volume; and

   -  peak and off-peak travel requirements and travel times must be
      incorporated.

Specific representational requirements identified in our policy
research include representation of:

   -  congestion management alternatives including traffic operations,
      pedestrian and bicycle facilities, parking management, freight
      movement options, congestion pricing, and incident management;

   -  operational alternatives including multiple general purpose
      lanes as well as intersection and roadway width, channelization
      and access management, traffic surveillance

TRANSIMS Model Design Criteria as Derived From Federal Legislation  29



             Derived Functional Requirements for TRANSIMS

      and control systems, motorist information systems, ramp
      metering, traffic control centers, and computerized signal
      systems;

   -  measures to encourage high occupancy vehicle (HOV) use such as
      HOV lanes, HOV ramp bypass lanes, guaranteed ride home programs,
      and employer trip reduction ordinances;

   -  public transit capital improvements such as exclusive rights-of-
      way (rail and bus) bus bypass ramps, park and ride as well as
      mode change facilities, and paratransit facilities;

   -  public transit operational improvements such as service
      enhancement or expansion, signal preemption, fare reductions,
      and transit information systems; and

   -  intelligent vehicle highway system (IVHS) characteristics and
      technologies.

Proposed Measures of Effectiveness(MOE) include:

   -  level of service (LOS);

   -  vehicle miles of travel (VMT) and average daily traffic by
      vehicle class;

   -  number of vehicles and persons using HOV (and other) lanes;

   -  proportion of travel, persons and vehicles congested or de

   -  proportion of travel time under congestion or delay;

   -  nature and location of congestion and incidents;

   -  delay per: lane mile, VMT, trip, vehicle, person, incident, and
      construction;

   -  average travel time per trip;

   -  persons/hour on facility or corridor; and

   -  persons per vehicle.

Air Quality Simulation.  Selected results of the travel simulation,
along with local meteorological characteristics (Atmosphere) and
surface characteristics (Land Use), should be applied to a separate
air quality simulation that determines vehicle emissions by pollution
type.  The resulting surface chemistry data must be accumulated, along
with background emissions from non-mobile sources, in space and time. 
As a function of regional meteorological conditions, these accumulated
surface emissions must then be applied to air chemistry and dispersion
models to determine where, to what extent, and for how long selected
levels of pollution accumulate in the atmosphere.  Although the
physical processes associated with each of these supporting submodels
is reasonably well understood, determining appropriate sampling
intervals and levels of aggregation present analysis and design
requirements to the TRANSIMS.

General representational requirements identified in our policy
research include:

   -  sensitivity to ambient temperature;
   -  representation of construction-related fugitive PM-10;

   -  representations that are in accordance with acceptable
      professional practice, and reasonable for purposes of emission
      estimation; and

   -  validation within the last 10 years against vehicle ground
      counts.

30  TRANSIMS Model Design Criteria as Derived From Federal Legislation



             Derived Functional Requirements for TRANSIMS


Specific representational requirements identified in our policy
research include representation of:

   -  vehicle speed and acceleration;

   -  vehicle, fuel, and engine characteristics; and

   -  startup (Hot vs.  Cold Start) and idling.

Analysis Support Environment.  Transportation and air quality planners
who use TRANSIMS will require, along with raw output data, hardware
and software that will allow them to effectively interpret and analyze
that data.  TRANSIMS, therefore, has a requirement to develop a set of
computer-based tools that support experimental design, sensitivity and
statistical analysis, and visual representation in multiple media. 
These tools will support all of the functional components of the
TRANSIMS environment:

   - Data Base development and review:

         Land Use,

         Transportation Population,

         Transportation System, and

         Atmosphere;

   -  output Data review and manipulation:

         Disaggregation Simulation

         Travel Planner

         Transportation Simulation. and

         Air Quality; and

   -  model review.

TRANSIMS Model Design Criteria as Derived From Federal Legislation  31



               Definitions, Acronyms, and Abbreviations

8.0       Definitions, Acronyms, and Abbreviations

The definitions of all terms, acronyms and abbreviations are presented
in this section.

CAAA      Clean Air Act Amendments of 1990
CMS       Congestion Management System
CO        Carbon Monoxide
DOT       US Department of Transportation
EIS       Environmental Impact Statement
EPA       Environmental Protection Agency
FHWA      Federal Highway Administration
FTA       Federal Transit Administration
HOV       High Occupancy Vehicle
IMS       Intermodal Facilities and Systems Management System
ISTEA     Intermodal Surface Transportation Efficiency Act of 1991
ITS       Intelligent Transportation System
MPO       Metropolitan Planning Organization
NAAQS     National Ambient Air Quality Standards
NHS       National Highway System
PM-10     Particulate Matter less than 10 microns in diameter
PMS       Pavement Management System
PTMS      Public Transportation Facilities and Equipment Management
          System
SIP       State Implementation Plan
SMS       Highway Safety Management System
STIP      State Transportation Improvement Program
TCM       Transportation Control Measure
TIP       Transportation Improvement Program
TMA       Transportation Management Area
TMS       Traffic Monitoring System
TSM       Transportation System Management
VOC       Volatile Organic Compounds
VMT       Vehicle Miles of Travel

32  TRANSIMS Model Design Criteria as Derived From Federal Legislation



                              References

9.0   References

Ducca, F. (1994) "Future Directions in Travel Forecasting" Department
of Transportation, Federal Highway Administration.

Federal Register (1993) Part HI: Environmental Protection Agency. 40
CFR, Part 5 1: Criteria and Procedures for Determining Conformity to
Transportation Plans; Proposed Rule.

Federal Register (1993) Part III: Department of Transportation,
Federal Highway Administration, and Federal Transit Administration. 23
CFR Part 450 (FHWA) and 49 CFR Part 613 (FTA) Statewide Transportation
Planning and Metropolitan Planning; Proposed Rule.

Federal Register (1993) Part IV: Department of Transportation, Federal
Highway Administration, and Federal Transit Administration. 23 CFR
Part 500 et. al. (FHWA) and 49 CFR Part 614 (FTA) Management and
Monitoring Systems; Proposed Rule.

Federal Register (1993) Part III: Department of Transportation,
Federal Highway Administration, and Federal Transit Administration. 23
CFR Part 450 (FHWA) and 49 CFR Part 613 (FTA) Statewide Transportation
Planning and Metropolitan Planning; Proposed Rule.

Federal Register (1993) Part II: Department of Transportation, Federal
Highway Administration. and Federal Transit Administration. 23 CFR
Part 450 (FHWA) and 49 CFR Part 613 (FTA) Statewide Transportation
Planning and Metropolitan Planning; Rule.

Federal Register (1993) Part II: Department of Transportation, Federal
Highway Administration, and Federal Transit Administration. 23 CFR
Part 500 et. al. (FHWA) and 49 CFR Part 614 (FTA) Management and
Monitoring Systems; Interim Final Rule.

Federal Register (1993) Part II: Environmental Protection Agency. 40
CFR, Part 51: Air Quality: Transportation Plans, Programs, and
Projects; Rule. 93 CFR Federal or State Implementation Plan
Conformity; Rule.

Harvey, G and E. Deakin (1992) "A Manual for Transportation Air
Quality Modeling for Metropolitan Planning Organizations" November 30,
1993 Revised Draft prepared for the National Association of Regional
Councils.

Karash, K., C. Schweiger, and L. Harman (1994) "Identification of
Transportation Planning and Data Collection Requirements in Federal
Legislation" prepared for the Volpe National Transportation System
Center.

TRANSIMS Model Design Criteria as Derived From Federal Legislation  33






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