Since 2009 the Texas Department of Transportation (TxDOT) has posted a list of the most congestedroadway sections in the state on its website (1). This list is produced annually by TxDOT and the TexasTransportation Institute (TTI) using a jointly-developed methodology. The two agencies have developedan approach that combines traffic speed data from annual archives of private sector data companies, basicroadway geometry, and traffic counts published in the TxDOT statewide roadway inventory file (RHiNo)(2) to calculate congestion-related performance measures. A set of volume distribution curves, combinedwith daily traffic counts, is used to estimate 15-minute volumes for each average day of the week. Theseestimated 15-minute volumes are combined with 15-minute speed data to calculate delay. Performancemeasures such as annual delay per mile, congestion cost, and the Travel Time Index are produced fromthis analysis and are used to rank the congested segments across Texas. This paper describes the processused to produce these statistics.
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