Staff Responsibility: William Hyman and Abdelmename Hedhli
Travel time reliability monitoring systems (TTRMS) can help transportation agencies—especially those with transportation management centers—monitor the performance of their system, understand the impacts of the various influencing factors, provide credible information to the system users about what travel time reliability to expect, and decide what actions to take to help improve reliability.
The objective of this project was to develop system designs for programs to monitor travel time reliability and to prepare a guidebook that practitioners and others can use to design, build, operate, and maintain such systems.
This research project conducted a survey of the state-of-the-art and state-of-the-practice in travel time reliability monitoring systems worldwide. The findings from the survey were coalesced into a set of use cases that became the drivers for the TTRMS functional specifications. The project also conducted an analysis of recommended sensor spacing and sampling rates. A suite of methods was developed for the TTRMS so that it could create travel time reliability information from the data assembled; the objective of these methods is to create probability density functions for highway segments, which can be used to create density functions for routes. To validate the TTRMS developed in this project, five case studies were conducted where prototypes of the TTRMS were put in place: San Diego, Sacramento/Lake Tahoe, Northern Virginia, Atlanta, and New York City.
The main product of this research is a guidebook, which describes how to develop and use a TTRMS. It explains why such a system is useful, how it helps agencies do a better job of managing network performance, and what a traffic management center team needs to do to put a TTRMS in place. The guidebook describes the process of measuring, characterizing, identifying, and understanding the effects of recurrent congestion and nonrecurring events that affect travel time reliability; and it provides information on the functional specification of a monitoring system, methodological details, a series of case studies, and a series of use cases (applications) of the guidebook.
Project Status: This project is complete.
Product Availability: The final report is available at https://www.trb.org/Main/Blurbs/168765.aspx, and the guidebook is available at https://www.trb.org/Main/Blurbs/168764.aspx. The guidebook and a corridor-level queuing prediction model, which was also developed in this project, will be tested in SHRP 2 Project L38 (Pilot Testing of SHRP 2 Reliability Analytical Products). More information about this model and the pilot test can be found on the following page.
