The Texas Transportation Institute (TTI) is considered a national leader in providing congestion and mobility information. The Urban Mobility Report (UMR) is the most widely quoted report on urban congestion and the associated costs in the nation. The report measures system delay, wasted fuel, and the annual cost of congestion in all U.S. urban areas. In 2011, researchers also produced the Congested Corridors Report (CCR) which focused on traffic congestion along 328 corridors across the U.S. The CCR is the first report to include travel reliability statistics on a nationwide basis. In recent years, the UMR/CCR researchers partnered with a private-sector historical speed provider–INRIX–to obtain nationwide speed data to generate the best possible estimate of mobility conditions across the nation. The data that are available from this partnership continue to allow the UMR/CCR methodology to evolve. While much more is understood about freeway operations and mobility, the INRIX data are allowing researchers to take a closer look at arterial street operations and mobility. This report describes a methodological improvement in the UMR arterial street congestion calculations, including a change in the definition of “free-flow speed,” which is used for delay calculations on arterial streets. This research improves the estimates of congestion and its costs, and maintains TTI’s position as the most authoritative source of mobility and congestion information. (Author/publisher)
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