For almost twenty years the Texas Transportation Institute (TTI) has produced urban congestion and mobility information that can be understood by a wide range of stakeholders. The statistics, charts and figures are regularly used to discuss the transportation challenges facing cities and the nation. The information is updated annually and occasional improvements to the methodology are made to include the mobility effects of a broad range of transportation projects, programs and strategies.
As more and better information is generated each year in the transportation industry, the need arises almost annually to make adjustments to the Urban Mobility Report calculation procedures. One of the key calculations in the Urban Mobility Report is the speed estimation procedure. This process assigns peak period operating speeds to varying traffic densities on freeways and principal arterial streets. More is learned each day about the relationship between traffic levels and speed with the influx of real-time traffic data that is collected in our many transportation management centers across the United States. This data will make it possible to revisit the current methodology and determine if adjustments need to be made to several parts of the methodology including the speed estimation process.
The project had four objectives.
(1) Analyze the speed estimation and accompanying measure calculation procedures utilized in the Urban Mobility Report to determine if they need to be modified based on real-time data or more current models.
(2) Determine if an areawide reliability performance measure can be calculated for inclusion in the Urban Mobility Report.
(3) Review the methodology that quantifies the benefits of operational treatment programs and strategies.
(4) Construct a spreadsheet that individuals or groups that can use to gain further insight from the data.
The research is complete and has been incorporated into the TTI Urban Mobility Report. Copies of the task papers are available by request from the NCHRP.