Skip to content

How We Got the Numbers

2009 Urban Mobility Report: Methodology – What's New for 2009

Since You Asked, Here's Why the Numbers Are Different

Each Urban Mobility Report reviews procedures, processes, and data used to develop the best estimates of the costs and challenges of traffic congestion, improving them when possible. The methodology was revised in 2008/9 to improve the public transportation methodology. In addition, the benefits from operations treatments were estimated throughout the extent of the study database to improve the relevance of the long-term trends. This caused some numbers from previous reports to change. All of the congestion statistics in the 2009 Urban Mobility Report have been revised using the new calculation procedures for all years from 1982 so that true trends can be identified.

Changes to Congestion Methodology – Highlights
  • Public transportation – An improved method for transferring riders back into the roadway network to simulate the effect of eliminating public transportation service resulted in larger delay reduction benefits in the 2009 report. The new methodology was reapplied for all previous years as well. Improvements include using the transit modes in each region to determine the peak travel mileage and alternative routes.
  • Operations benefits - The 2009 report estimates the benefits from programs that reduce congestion without adding roadway lanes for every year since 1982. Previous reports included these programs only since 2000. There are fewer data for the pre-2000 period, but general trend information and project-specific reports were used to smooth out what had been a disruptive element the urban area congestion trends.

The base data for this report are from the Federal Highway Administration's Highway Performance Monitoring System (1). More information on the methodology is included at: http://mobility.tamu.edu/ums/report/methodology.stm.

Information About: