Washington, D.C. – Members of the National Capital Region Transportation Planning Board (TPB) were briefed today on findings from the 2008 aerial traffic congestion survey, which highlight several areas of increased congestion throughout the region. The survey, which is conducted every three years, indicates changes in congestion locations and durations in comparison to earlier surveys.
Overall, traffic congestion in the region has decreased since 2005. Ron Kirby, Director of Transportation Planning at the Metropolitan Washington Council of Governments (COG), said much of the reduction can be attributed to a decrease in Vehicle Miles Traveled (VMT). “This is the first time since we began monitoring traffic congestion that VMT has dropped since the previous survey,” Kirby said.
Most congested freeway chokepoints in the region in 2008:
Southbound Southwest Freeway (5:30 to 6:30 p.m.) from Southwest Freeway/I-395 to U.S. Route 1*
Westbound 11th St. Bridge (8:00 to 9:00 a.m.) from I-295/D.C. 295 to Southeast Freeway
Northbound Southeast Freeway (4:30 to 6:30 p.m.) from 11th St. to Pennsylvania Ave.
Outer Loop I-495 (8:00 to 9:00 a.m.) from New Hampshire Ave. to U.S. 29*
Inner Loop I-495 (5:30 to 6:30 p.m.) Georgetown Pike to George Washington Parkway
Northbound Southwest Freeway (4:30 to 5:30 p.m.) from U.S. Route 1 to L'Enfant Plaza Exit
Eastbound I-66 HOV (8:00 to 9:00 a.m.) from VA 243 to I-495*
Eastbound I-66 (6:30 to 7:30 p.m.) from VA 267 to VA 693
Inner Loop I-495 (5:30 to 6:30 p.m.) from MD 187 to I-270
Northbound I-95 (7:00 to 8:00 a.m.) from VA 644 to I-495
*Indicates that these locations experienced an increase in congestion from 2005.
In addition to collecting information on these areas of acute congestion, for the first time the survey also identified corridors in the region that experienced sustained congestion over long distances. Eastbound I-66 from the VA 234 Bypass to I-495 takes the top spot in the morning peak period, with an estimated delay of 21 minutes. In the evening peak period, the Inner Loop of I-495 from VA 7 to the I-270 Spur experiences the longest delay at an estimated 16 minutes.
The survey of the region’s 300-plus mile freeway system was conducted over multiple days during the morning and evening peak periods. To determine the level of congestion on freeway segments, the survey measures density of passenger cars per mile per lane (pcpmpl). A pcpmpl of 40 or greater indicates congestion (30-55 mph), while 62 or greater indicates severe congestion (10-30 mph).
With higher gasoline prices and the onset of the economic downturn, VMT dropped by 3.1 percent from 2005 to 2008, and the overall number of lane miles identified as congested or heavily congested in both the morning and evening peak periods decreased significantly. Similar to the drop in VMT, the highest traffic density in 2008 (115 pcpmpl) was lower than the highest density in 2005 (130 pcpmpl). In addition to a reduction in VMT, localized improvements aimed at increasing capacity have also improved conditions.
The TPB has commissioned the aerial traffic surveys since 1993 to monitor congestion on the region’s freeways during morning and evening peak periods. To view the complete report, click here.