Urbanized Area Congestion — 23rd Annual Highway Report

Peak Hours Spent in Congestion per Auto Commuter (in hours)
2017 Annual Highway Report

There is no universally accepted definition of traffic congestion. In reporting to the federal government, the states have in the past used peak-hour traffic volume-to-capacity (V/C) ratios, as calculated in the Transportation Research Board’s Highway Capacity Manual, as a congestion measure. Through 2009, the Federal Highway Administration (FHWA) summed up these V/C calculations to determine the state mileage in various V/C categories. Since 2009, however, these tables have not been published by the FHWA. Instead, the FHWA has been reporting periodic statistics based on travel delays from mobile devices, but only for selected regions and roads, not for states.

This change by the FHWA has necessitated changes in this report’s state-level congestion metric. The 21st Annual Highway Report used data from the Texas A&M Transportation Institute’s Urban Mobility Report (UMR) to calculate a metric similar to the V/C metric above. The measure developed was the “percentage of the urban Interstate and freeway system that is congested,” which measured the extent of the urban congestion problem. Congestion, however, has three dimensions (intensity, duration and extent), so a better metric was needed to capture more fully these three aspects. New data from mobile devices provide this opportunity.    

The congestion measure used for the 22nd Annual Highway Report was also derived from the Urban Mobility Report, renamed the Urban Mobility Scorecard (UMS). The 2015 UMS was published jointly by the Texas A&M Transportation Institute and INRIX in August 2015, and reported data for 2014. The congestion measure selected, the “average annual delay per auto commuter (in hours),” captured delay in all three dimensions of congestion. It also had the advantages of being straightforward and relevant to the average citizen, was easily calculated, and was more current. Unfortunately, the UMS has not been updated and INRIX has changed the methodology for some of its internal metrics. Again, a new congestion measure is needed.

This study, the 23rd Annual Highway Report, uses data directly from the 2016 INRIX Global Traffic Scorecard, published in February 2017. The metric selected was the “peak hours spent in congestion per auto commuter annually.” This measure is also straightforward and relevant to the average citizen, is taken directly from the INRIX Scorecard and uses real-time traffic data.  For 2016, INRIX defines congestion as a speed below 65% of the free-flow speed, which is the typical uncongested speed on that road segment, and defines peak hours locally based upon the actual driving habits in each city, as opposed to the more typical fixed peak periods of 6:00 AM–9:00 AM and 4:00 PM–7:00 PM. (The INRIX data, which are computed only for selected cities, are extended to all U.S. metropolitan areas and then rolled up by state. See Appendix for details.) Since this newer measure is different from the congestion measures used before, direct comparisons from previous reports are not possible. With this new measure, some states will see gains and others will see declines; it will likely take a few years for this measure to stabilize. Additionally, as real-time individual driver data become more prevalent, this measure will more accurately reflect actual road conditions.

In 2016, the average annual peak hours spent in congestion in the urbanized areas across the United States was 34.95 hours (see Table 14, Peak Hours Spent in Congestion per Auto Commuter, Figure 5). Annual peak hours spent in congestion range from 5.86 in Wyoming to 72.53 in New Jersey. The congestion problem is primarily concentrated in the major cities of just a few states. Only the bottom nine states exceed the U.S. congestion delay average and their totals skew the average peak hours spent in congestion upward.    

Peak Hours Spent in Congestion Per Auto Commuter (in hours)