Overview
This final report documents the activities performed during SHRP 2 Reliability Project L08: Incorporating Travel Time Reliability into the Highway Capacity Manual. It serves as a supplement to the proposed chapters for incorporating travel time reliability into the Highway Capacity Manual prepared for this same project. The proposed chapters demonstrate how to apply travel time reliability methods to the analysis of freeways, urban streets, and corridors. The final report summarizes the work activities conducted during the course of the Phase 1 and Phase 2 research by memorializing the activities, the processes, and the findings of the L08 project. In this way, the final report articulates the how and why of key decisions made and key activities undertaken during the project so that the logic and rationale are not lost to future researchers and practitioners who aim to build on the work completed in this effort.
This report addresses the following topics:
- The project’s purpose, objectives, and work tasks (Chapter 1);
- The research team’s proposed definition of reliability, along with means for measuring reliability (Chapter 2);
- A state-of-the-art and state-of-the-practice literature review (Chapter 3);
- An overview of the methodologies for calculating reliability for freeways and urban streets (Chapter 4);
- A description of the development of freeway and urban street scenario generators (Chapter 5);
- Enhancements to the Highway Capacity Manual (HCM) freeway facilities methodology and its computational engine FREEVAL-RL (FREeway EVALuation—ReLiability), and enhancements to the urban streets methodology and its computational engine STREETVAL (STREET eVALuation) (Chapter 6 and Appendices A and B);
- A procedure for conducting a corridor application (Chapter 7); and
- A method for future consideration to define levels of service using reliability as a service measure and a discussion of future research needs (Chapter 8). The remainder of this executive summary provides a brief overview of the research results.