August 29, 2007

Metropolitan Travel ForecastingTRB Special Report 288

Mn/DOT Statewide Travel Demand Modeling Committee

August 29, 2007

August 29, 2007

Background

Environmental Defense Fund vs. Metropolitan Washington Council of Governments

National Research Council peer review convenes to determine is MWCOG travel demand modeling process “state of the practice”

FHWA, FTA, OST funded TRB Special Report 288 – “Metropolitan Travel Forecasting”

August 29, 2007

“Although travel demand models have been used in transportation planning for some four decades, there are few universally accepted guidelines or standards of practice for these models or their application” (TRB 2003).

August 29, 2007

TRB Special Report 288 - Objectives

1. Describe current state of the practice

2. Evaluate current state of the practice, including deficiencies

3. Recommend improvements

http://onlinepubs.trb.org/onlinepubs/sr/sr288.pdf

August 29, 2007

TRB Special Report 288 - Process

Established high level committee Conducted a web based survey of all

MPOs Reviewed literature Interviewed 16 states and MPOs Invited presentations from federal

agencies

August 29, 2007

General Observations

Despite changes in travel demand modeling responsibilities & expectations the basic practice has changed little in recent years

Most urban travel demand models are not based on a coherent theory of travel behavior – Meyer and Miller, 2001

Travel demand models are deterministic in an environment that is increasingly more complex and probabilistic

There are no commonly agreed upon standards for an acceptable range of error

August 29, 2007

General Observations - Continued

Gravity models may be insensitive to policy, socioeconomic or geographic variables that influence travel behavior

Resource constraints hamper many seeking to improve data inputs and strengthen modeling practices

There are a number of MPOs and State DOTs implementing improved practices for model estimation, model calibration, and model validation

August 29, 2007

TRB 288 - Findings

The basic modeling approach remains a sequential 4-step process Some are experimenting with tour-based

models and land use + travel models There is no single approach that is “correct”

for all applications or all MPOs. Travel forecasting tools should be

appropriate for the questions being posed and the analysis being conducted.

August 29, 2007

Snapshot of Survey Results

16 states provide MPOs with guidance aimed at standardizing modeling practice

14 states perform model development and forecasting for many or all MPOs in their state

89% of MPOs with population exceeding one million do their own model development

16 states have statewide MPO model user groups 70% of large & medium MPOs identified modeling features

that need improvement About 20% of small & medium sized MPOs & almost 40%

of large MPOs are considering replacing existing models with activity or tour based models

August 29, 2007

Shortcomings

Demands on forecasting models have grown. Existing models are inadequate to address many newer policy concerns, including: Estimating motor vehicle emissions based on speeds

and time of day Estimating new travel generated by new capacity –

induced travel Evaluating alternative land use policies Estimating freight movements & non-motorized trips

Modeling yields less satisfactory results as problems being studied become more disaggregate & more linked to individual travel behavior

August 29, 2007

Shortcomings (2)

Current models have inherent weaknesses in: Associating traveler characteristics with trips Dealing with time of day variations & peak

spreading Estimating traveler responses to:

Congestion Public policy changes such as road pricing, land use

controls, transit vouchers Emergencies

Considering travel impacts from demographic changes & estimating transportation affects on economic development

August 29, 2007

Shortcomings (3)

Poor technical practice Inadequate data Failure to deal with uncertainty in model

estimates Inability to represent dynamic conditions Reliability of land use and demographic

forecasts Failure to maintain consistency among all

elements of a forecast, especially around growth & land use projections

Lack of validation processes & procedures

August 29, 2007

Improvements to the 4-Step Process

Improved measure of arterial congestion(modeled delay at arterial intersections)

Inclusion of both highway + transit in trip distribution

Improved trip distribution models (destination choice)

Improved modeling of non-motorized trips

Improved sensitivity (validation) testing

August 29, 2007

Advanced Models

Three metropolitan areas/regions have implemented advanced models; 8 more are in design

Reflect decision patterns/interactions of households

More completely represent supply-side network to account for details of congestion throughout the day

August 29, 2007

Advanced models - continued

1. Improved land use models2. Tour based models that recognize that trips have

multiple purposes and stops3. Activity based models that recognize complex

interactions between activity & travel behavior & are capable of producing regional scale microsimulation

4. Discrete-choice modeling - travel made by individuals not TAZs

5. Supply-side models6. TRANSIMS

August 29, 2007

FTA Model

New Starts program requires before and after studies

Applicants must certify the adequacy of technical methods, including best available data and quality assurance reviews

Must use the SUMMIT FTA reporting tool to calculate user benefits and assess quality control

FTA & FHWA conduct certifications of every TMA at least every 4 years to ensure adequacy of the planning process

August 29, 2007

Obstacles

Can advanced models be implemented for reasonable costs and provide significant improvements?

Federal involvement & funding for models has decreased and is severely deficient – yet federal planning and environmental requirements have increased

August 29, 2007

Barriers to Change

Resource limitations Uncertainty about whether new models will

be better than the ones they replace Lack of coordination among stakeholders Inadequate investment in development &

transfer of new techniques

August 29, 2007

Additional Barriers

“…virtually all MPOs believe it is either difficult or very difficult to hire experienced travel modelers”. (UTM 2006)

Unavailability of vendor supplied software to address shortcomings & needs

August 29, 2007

MPO Recommendations

1. Create a national metropolitan cooperative research program Pool resources for modeling

enhancements Cooperate in research and

development studies

2. MPOs should conduct formal peer reviews of their modeling practices

August 29, 2007

MPO Recommendations (Continued)

3. Individual MPOs & universities could form partnerships to foster research & implementation of advanced practices

4. MPOs and other planning organizations should conduct reasonableness checks of demand and costs forecasts for major projects

5. MPOs with advanced modeling practices should document and share experiences

August 29, 2007

State Transportation Agency Recommendations

1. Support development of a national MPO cooperative research program

2. Provide support for model user groups3. Work in cooperation with MPOs to evaluate

socioeconomic forecasts4. Coordinate with MPOs on statewide and

metropolitan models & data needs

August 29, 2007

Federal Government Recommendations

1. Support & provide funding for incremental improvements to 4-step and trip-based models

2. Support & provide funding for advanced approaches, including activity based modeling

3. Continue TMIP 4. Increase funding to support modeling 5. Continue the MPO certification process with

checklists to clarify minimum expectations6. Allow MPOs substantial flexibility in their

travel demand practices

August 29, 2007

Opportunities for Intergovernmental Cooperation

1. Establish appropriate goals, responsibilities, and means of improving travel forecasting practices

2. Compare the performance of conventional vs. traditional models

3. Collaborate on data collection Updating travel surveys Collecting freight flows Expanding traffic counts Measuring traffic speeds

August 29, 2007

Questions for Minnesota Modelers

1. How well is the traditional 4-step process meeting your needs?

2. Do you agree with the limitations outlined in TRB 288?3. From your perspective, how serious are the limitations

cited in the report? To what extent do these limitations negatively

influence your ability to effectively forecast future conditions and/or address policy, program, or project questions and decisions in your area?

Of the limitations cited in the report, which are most problematic? Which currently have little or no impact on forecasting results of your plans, policies, or programs?

August 29, 2007

4. What is your reaction to the recommendations included in the report?

Which of the recommendations would be most helpful in strengthening metropolitan forecasting?

Do you have additional ideas or suggestions for improving existing data, models, processes or procedures?

5. What actions, strategies or process changes have you implemented to enhance metropolitan forecasting?

August 29, 2007

Thank you!

Please forward comments, ideas and suggestions to:

Jonette Kreideweis

651-366-3854

jonette.kreideweis@dot.state.mn.us