This report documents the research of the L02 project, Establishing Monitoring Programs for Travel Time Reliability. The main work product from the project is the Guide to Establishing Monitoring Programs for Travel Time Reliability. The Guide discusses how to develop and use a travel time reliability monitoring system (TTRMS). (Accompanying the Guide is a brief, stand-alone document that provides suggestions for communicating information about time travel reliability using maps, figures, and tables. The document, Handbook for Communicating Travel Time Reliability Through Graphics and Tables, and the Guide are available at http://www.trb.org/Main/Blurbs/168764.aspx.) The purpose of this report is to describe the process that led to the development of the Guide and the Handbook. A TTRMS can help operating agencies monitor system performance, understand the impacts of the various factors that influence travel time, and provide credible information to the system users about what travel time reliability to expect. With this information, operating agencies can make better decisions about what actions to take to help improve reliability. At the time this research was performed, most transportation agencies did not have these capabilities. One of the most important findings of the L02 project is that reliability is best described by creating holistic pictures such as probability density functions (PDFs) and their associated cumulative density functions (CDFs). Thus, rather than characterize reliability in mathematical terms, graphs of the PDFs and CDFs make it easy for one to visualize reliability and various regimes consisting of different combinations of congestion levels and types of nonrecurring events (e.g., incidents, weather, and work zones). The research began with a survey of the state of the art and state of the practice in travel time reliability monitoring systems worldwide. The team then focused on the TTRMS and its primary functions listed above. Finally, the team sought to validate the TTRMS concept by building prototypes of elements of the TTRMS in five locations: San Diego, Sacramento and Lake Tahoe, Northern Virginia, Atlanta, and New York City. Systems that can be used to develop distributions of travel times over long periods, for both highway segments and travel from origins to destinations, will be the foundation for analysis and decisions that improve reliability. (Author/publisher)
Samenvatting