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Transportation Air Quality Selected Facts and Figures

Traffic Congestion

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Is Traffic Congestion in Our Cities Getting Better or Worse?

Congestion occurs when the free flow of traffic on a roadway is impeded due to excess vehicle demand, construction, maintenance, traffic incidents, weather, or other road conditions and events.

Before the 2008 economic recession, congestion was increasing at between 2 and 4 percent every year–which meant that extra travel time for the average commuter increased slightly less than 1 hour every year. The economic recession set back that trend a few years, but the trend in the last few years indicates congestion is rising again.

This map shows the percent change from 2011 to 2014 in the amount of time per trip it took to travel in the peak period for selected areas.

Changes in Traffic Congestion (2011–2014)

Title: Map of the continental United States showing changes in traffic congestion in major cities from 2011 to 2014 - Description: The map shows the percent change from 2011 to 2014 in the amount of time per trip it took to travel in the peak period (or rush hour) for 27 metropolitan areas. The values range from a decrease of 0.7% in Washington, DC, to an increase of 3.1% in Houston. Washington, DC, had the only decrease, nine areas showed no change, and the remainder showed an increase between 0.8% and 3.1%.

Source: Texas A&M Transportation Institute, 2015 Urban Mobility Report, August 2015, Table 1, http://d2dtl5nnlpfr0r.cloudfront.net/tti.tamu.edu/documents/mobility-scorecard-2015.pdf

What Are the Major Sources of Congestion?

FHWA studies show that congestion is the result of seven root causes, often interacting with one another.

Source: Federal Highway Administration, Traffic Congestion and Reliability: Linking Solutions to Problems Report, July 2004, http://ops.fhwa.dot.gov/congestion_report_04/index.htm#toc

Updated: 5/3/2016
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