View
217
Download
0
Category
Tags:
Preview:
Citation preview
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
Recommended