But the outside traffic analysts say the true picture of traffic in the area over the past year is more complicated and likely not so rosy. Vehicle counts probably fell, they say, because traffic grew so clogged that fewer motorists even reached the mechanical counters during the allotted times. Local residents say that explanation jibes with their daily misery: growing backups extending into downtown Bethesda, gridlocked intersections, and rush hours that now begin as early as 6 in the morning and 2:30 in the afternoon.
Paul Schonfeld, a University of Maryland transportation engineering professor, hasn’t reviewed the military’s analysis but said the idea that worsening traffic congestion would coincide with fewer vehicles “doesn’t sound particularly reasonable to me.”
Finding ways to accommodate new traffic is a key concern with many military base expansions, as Fort Meade and Fort Belvoir also experienced during the past year under the Pentagon’s base realignment process.
But moving Walter Reed from the District to consolidate operations on the Bethesda campus of the former National Naval Medical Center was considered particularly challenging because of its dense, highly residential location. Even without additional traffic from the base, the surrounding roads were heavily congested commuter routes between the Maryland suburbs and the District and carried local traffic between Bethesda, Rockville, Kensington, Chevy Chase and Silver Spring.
State and local transportation planners rated the intersections around the Bethesda base as “failing” even before 3,600 new employees moved there during the expansion. The influx of personnel increased the base’s total workforce 44 percent, to 11,686 people. More strikingly, patient visits are on pace to double, to an annual 1 million, with most expected to arrive by car.
The explanation of why traffic counts can improve as congestion worsens is a grim lesson in traffic physics. Faced with additional vehicles, intersections already stretched beyond capacity end up with bigger backups. At some point, engineers say, intersections deteriorate into an inefficient mess. Motorists must sit through two or more cycles of a green light, and intersections end up blocked by cross-traffic that can’t move.