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January 31, 2012

Aerial Survey of Region's Freeways Shows Congestion Relief in a Few Locations, But Worsening Conditions Overall

Between 2008 and 2011, the number of lane-miles of freeway in the Washington region with moderate or severe congestion during peak traffic periods increased by 31%, according to a recent aerial traffic survey by the Transportation Planning Board.

In a few locations, where key improvement projects have opened or been completed since the last survey in 2008, congestion has been greatly reduced. But in others, construction projects and long-standing bottlenecks continue to contribute to lengthy travel delays for drivers.

The most significant reduction in peak-period congestion identified in the 2011 survey was in the vicinity of the Woodrow Wilson Bridge between Prince George's County, Maryland, and Alexandria, Virginia, where an aging 6-lane structure was replaced with a new 10-lane span.

In the westbound direction during the morning peak, segments of the Capital Beltway on and near the Wilson Bridge that saw travel speeds frequently drop below 20 miles per hour in 2008 were found in 2011 to have free-flowing travel speeds of 55 to 65 miles per hour.

The replacement of the Wilson Bridge had long been part of the region's financially constrained long-range transportation plan, or CLRP, which is maintained by the TPB and lists all "regionally-significant" transportation projects and programs that the Federal government and state and local governments in the region plan to build or implement in the coming decades.

A number of other major improvement projects in the CLRP -- the Inter-County Connector (ICC) in Maryland, for example, and new High-Occupancy/Toll (HOT) lanes on the Capital Beltway in Virginia -- were under construction when the 2011 survey took place. Reconstruction of the 11th Street Bridge in the District of Columbia and the first phase of the Metrorail extension to Dulles Airport were also underway. The next aerial survey, planned for 2014, is expected to show that the completion of these projects has brought congestion relief to some critical corridors in the region.

Although these and other construction projects contributed in part to the 31% increase in the total number of lane-miles of freeway congestion in the region between 2008 and 2011, the most recent survey found many ongoing trouble spots that will need attention in future updates to the CLRP.

In particular, the survey identified the region's "top ten" routes experiencing the greatest estimated travel delay during peak periods, as well as the region's "top ten" most congested bottlenecks.

The I-95/I-395 corridor from US 1 near Woodbridge, Virginia, north to the 14th Street Bridge was found to be the route with the greatest estimated travel delay. A trip along that route that would take approximately 18 minutes in free-flow conditions was found to take almost 63 minutes during the morning peak.

The northernmost segment of I-395 in Virginia, between Washington Boulevard and Jefferson Davis Highway, was found to be the region's most congested bottleneck, with morning peak period speeds averaging just 5 miles per hour. A proposal to construct HOT lanes and to provide commuter bus service in the I-395 corridor from Edsall Road to Eads Street in Arlington was removed in the 2011 update to the CLRP.

While the 2011 aerial traffic survey revealed welcome relief of freeway congestion in some locations, continuing growth in the total number of congested lane-miles of freeway during the morning and evening peak periods underscores the ongoing transportation planning challenges facing the region.

Related Links

• Traffic Quality on the Metropolitan Washington Area Freeway System: Spring 2011 Report (10/4/11)

• TPB Briefing on 2011 Peak Period Freeway Congestion in the Washington Region, and Changes Since 2008 and 2005 (12/21/11)

• Past Survey Reports: 2008, 2005, 2002

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