OBJECTIVE

The objective of this project was to enhance the guidance in the Highway Capacity Manual for the selection and use of alternative traffic analysis tools.

STATUS

The research results were incorporated into the Highway Capacity Manual 2010.

BACKGROUND

Traffic analysts often use simulation and other models in conjunction with, or instead of, Highway Capacity Manual (HCM) procedures to evaluate traffic operational quality and estimate capacity. Such models may be used (1) when HCM methods do not address a particular facility configuration or traffic demand scenario or (2) to supplement the findings of HCM analysis.

In 2000, Part V was added to the HCM to address some of the questions regarding application and use of simulation and other models in highway capacity analysis. Part V discusses traffic simulation and other models and provides typical applications of such models in traffic operational analysis. The existing Part V is general in scope, however, and does not provide sufficient guidance on the use of such models for each facility type to conduct highway capacity analysis or to obtain capacity and level-of-service (LOS) estimates.

TASKS

Task 1. Critically review the Traffic Analysis Toolbox and other relevant literature to identify material suitable for inclusion in the HCM as guidance for selection and use of simulation and other models.

Task 2. Review how LOS is used in different types of analyses, how LOS is derived from the outputs of simulation and other models, and the appropriateness of doing so.

Task 3. Identify and describe limitations of HCM methodologies that would lead an analyst to consider using simulation and other models.

Task 4. List and describe currently available simulation and other models that are commonly used to replace or augment HCM analysis. Identify those limitations from Task 3 that each model should be able to address.

Task 5. Within 6 months of the contract start, submit an interim report summarizing the work done in Tasks 1 through 4. The interim report should include a refined work plan for the remaining project tasks and a detailed outline of the new Part V that will be fully developed in Task 8.

Task 6. Determine relationships among measures of effectiveness commonly reported by simulation and other models and those used in the HCM. As appropriate, develop methods for numerically translating measures of effectiveness between models. Cases where this translation is not appropriate should be explained.

Task 7. Develop and describe approaches to properly present the results of simulation and other models (including comparison to the results of an HCM analysis) so that analysts and decision makers can more easily interpret the analysis results.

Task 8. Draft a new Part V for the HCM, including general guidance on selecting and using alternative models and their cost implications. Provide specific guidance on presenting and interpreting the results of simulation and other models.

Task 9. Submit a final report summarizing the entire research effort and including the HCM Draft Part V as an appendix. A separate appendix should list any recommended changes to Parts I through IV of the HCM that have been identified during the course of the project.

Task 10.  Examine the microscopic outputs of alternative analysis tools to seek a common ground for comparison of the outputs obtained from those tools.

Task 11.  Develop guidelines for the use of dynamic traffic assignment tools.