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Certification Checklist for Travel Forecasting Methods

Introduction

Federal transportation planning legislation requires each metropolitan planning organization (MPO) to develop a transportation plan as part of its planning process [23 U.S.C. 134 (g) and 49 U.S.C. 5303 (f)]. This transportation plan must cover at least a 20-year planning horizon, and "shall include both long-range and short-range strategies/actions that lead to the development of an integrated intermodal transportation system that facilitates the efficient movement of people and goods" [23 CFR 450.322].

A transportation plan requires valid forecasts of future demand for transportation services. These forecasts are frequently made using travel demand models, which allocate estimates of regional population, employment and land use to person-trips and vehicle-trips by travel mode, route, and time period. The outputs of travel demand models are used to estimate regional vehicle activity for use in motor vehicle emissions models for transportation conformity determinations in non-attainment and maintenance areas, and to evaluate the impacts of alternative transportation investments being considered in the transportation plan.

The Transportation Conformity Rule established a regulatory requirement that includes minimum specifications for travel models used to forecast vehicle activity for regional emission analyses in conformity determinations in certain non-attainment and maintenance areas [40 CFR 93.122 (b) and (c)]. However, these minimum specifications apply only to metropolitan planning areas with an urbanized area population over 200,000 that are also serious, severe or extreme ozone or serious carbon monoxide non-attainment areas. All other non-attainment or maintenance areas must continue to meet the minimum specifications for travel models established in the Conformity Rule to the extent that those procedures have been the previous practice of the MPO.

Although there are no other requirements that travel demand models must be used in the metropolitan transportation planning process, the travel forecasting methods used by an MPO should be addressed in the certification review to ensure that they adequately support the applications for which they are being used. These applications can vary considerably from one MPO to another, depending on such factors as non-attainment status, regional population and economic growth, and the types of strategies/investments being considered in the transportation plan.

The questions included in this checklist are designed to provide the certification review team with an overview of the travel forecasting methods being used by an MPO, the suitability of those methods for intended applications, and the technical capabilities of the planning staff in applying the methods. In those cases where responses to the checklist questions raise serious concerns on the adequacy of the forecasting methods, the certification review team should request a more in-depth review by FHWA Resource Center or FHWA/FTA Headquarters travel model experts.

Key Indicators of Risk

Determining the adequacy of an MPO's travel forecasting methods begins with an understanding of how the forecasts will be used. Where forecasts are used to estimate motor vehicle emissions for transportation conformity determinations, or where they are used to evaluate major transportation investment alternatives such as new highways or transit lines, the forecasting methods are more likely to be scrutinized. Federal findings (e.g., Conformity Determinations or Records of Decision) based on weak or poorly documented travel forecasting methods may be susceptible to legal challenges. Such challenges can, at a minimum, lead to time consuming legal proceedings and delays in project implementation. In some cases, courts have even overturned federal findings because of inadequate forecasts, resulting in costly supplemental analyses and additional project delays. Adverse court decisions also establish legal precedent, which can be used by plaintiffs in subsequent challenges against other transportation agencies.

The following questions probe whether an MPO's forecasting methods are more likely to receive close scrutiny from other agencies or outside advocacy groups.

Affirmative answers to any of the above questions indicate that the travel forecasting methods used by the MPO are likely to be scrutinized by travel modeling specialists working on behalf of agencies or organizations other than the MPO.

Key Indicators of Agency Technical Capabilities

The certification review team can obtain a general overall assessment of the technical capabilities of the staff responsible for developing and applying the travel forecasting tools used by an MPO by looking at a few key indicators. These indicators are covered in the following questions.

If another governmental agency provides required modeling technical expertise:

If contractors perform all travel model development:

If in-house staff actively participate in model development and application:

If a peer review was convened, the following information should also be obtained:

Documentation

Most of the questions raised with respect to travel forecasts can be addressed by adequate technical documentation of the input assumptions and the methods used to develop the forecasts. In addition, federal transportation planning regulations require such documentation [23 CFR 450.316 (d)].

The Certification Review Team should request and obtain readily available written, technical documentation from the MPO covering the following subject areas:

  1. An inventory of the current state of transportation in the metropolitan area.
  2. Key planning assumptions used in developing the forecasts.
  3. Descriptions of the methods used to develop forecasts of future travel demand.

Each of these subject areas is described more fully below.

1. Inventory of Current Conditions

The foundation for any forecast is a comprehensive and objective inventory of current conditions with respect to both transportation supply and demand.

The inventory documentation should include the following summary measures for the metropolitan planning area:

The data sources for summary measures should be identified, including descriptions of their currency and frequency of updates. Data sources that are significantly out-of-date should be identified as candidates for updating in future UPWPs.

Data on highway VMT and congestion summary measures should be consistent with, and/or derived from traffic monitoring data used in the TMA's Congestion Management System (CMS).

2. Planning Assumptions

The principal determinants of any long-range travel demand forecast are the planning assumptions about the growth and distribution of population, developed land, and individual travel preferences. If these assumptions are not consistent with statewide or regional controls or with past trends for the study area, they need to be explained and justified.

In non-attainment and maintenance areas, planning assumptions should be consistent with the joint FHWA/FTA/EPA Guidance on the Use of Latest Planning Assumptions in Conformity Determinations (January 18, 2001). This guidance is available at http://www.fhwa.dot.gov/environment/air_quality/conformity/policy_and_guidance/con_guid08.cfm.

The documentation of planning assumptions should, at a minimum, address the following expected changes in the study area:

Updates to the transportation plan should compare current population, employment and demographic characteristics with forecasts made in previous plan updates. Significant differences between previous forecasts and current conditions should be documented and explained, and assumptions should be revised, accordingly.

3. Forecasting Methods

The complexity of a study area's forecasting methods can vary considerably, depending on current transportation conditions, and on the future transportation investments and policies being evaluated. For example, an MPO with limited public transportation service and few or no choice riders may be able to use a simplified, off-model approach to estimate transit mode share, unless it plans to evaluate major public transit investments as part of its transportation plan. Alternatively, an MPO that plans to make significant investments in operational technology (e.g., areawide signal synchronization, ramp metering, etc.) may need to add a traffic micro simulation model to its model set.

The technical documentation of the travel forecasting methods or models should include the following information:

The technical documentation should be readily available to all interested parties, consistent with the public involvement provisions in the planning regulations [23 CFR 450.316 (b)(1)]. Technical documentation should be updated on a periodic basis to reflect changes in the models or the key planning assumptions used to develop the transportation plan.

MPOs that cannot provide written technical documentation, or whose documentation does not adequately cover the above subject areas, are vulnerable to legal challenges even if their planning assumptions and forecasting methods are otherwise satisfactory.

Suggested Actions by the Certification Review Team

MPOs that are able to provide adequate documentation of their forecasting methods and assumptions, and that have generally positive indicators of technical capabilities and low indicators of risk, require no further action by the certification review team.

The absence of any technical documentation, or documentation that does not adequately address key subject areas should be discussed as a recommended area for improvement during the certification review.

Indications of weak technical capabilities with respect to travel forecasting methods should also be discussed as a recommended area for improvement during the certification review. MPO's that have not had their travel forecasting methods recently peer reviewed should be encouraged to convene a peer review. FHWA provides financial support to MPOs for technical peer reviews through its Travel Model Improvement Program (TMIP).

MPOs engaged in high-risk applications (e.g., conformity determinations or controversial highway projects), and with indications of weak technical capabilities should have their forecasting methods reviewed by FHWA/FTA travel model experts.

Updated: 12/03/2012
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