Pedestrians faster than cars in Center City Philadelphia
According to "Heart of Phila. near standstill," subtitled "Center City’s clogged arteries," from the Philadelphia Inquirer. The pedestrian beat out the car by a couple minutes. Plus it's easier and cheaper "to park" although Philly has a godawful number of surface parking lots.
A bike would be even faster.
Now, I say that congestion isn't that bad in Downtown DC, but there is no question that roads like K and I Streets, 14th, New York and Florida Avenues in NE and NW, Wisconsin Avenue, especially in Friendship Heights, M Street NW, etc., are quite congested for key periods during the day and into the early evening. However, later, most streets are pretty dead.