This chapter provides guidance on the application of travel demand models to develop project traffic. It covers the fundamentals of travel demand modeling, selection of an appropriate model, project-level model validation and reasonableness check, and refinement of model output to obtain consistent traffic forecasts. If an acceptable model is not available for a project, then refer to Chapter 5.

The following sections provide guidance on the use of models to develop traffic projections for corridor, project, and RRR projects. This guidance applies only to areas where an adopted/endorsed model is available. Data requirements and the level of modeling effort vary by the type of project.

Corridor projects usually require the development of travel projections for either new or existing corridors and are used to make decisions which have important capacity and capital investment implications for longer segments. An evaluation of the model’s ability to accurately project travel demand in the corridor area should be made prior to its use. Based on the results of this evaluation, additional corridor specific validation and/or model refinement efforts may be necessary.

Specific project travel demand projections require the highest accuracy. These projections are commonly used to develop lane requirements and intersection designs and evaluate the operational efficiency of proposed improvements. An evaluation of the model’s ability to accurately project travel demand in the project area should be made prior to its use. Based on the results of this evaluation, additional project specific (subarea and/or corridor) model refinement efforts may be necessary.

Resurfacing projects require the development of future AADT projections only and require the least accuracy. As a result, the modeling effort required to develop travel projections for resurfacing projects is the least involved of the project types. Generally, a properly calibrated (area-wide) model can be directly applied without the need for additional evaluation or validation efforts.