Potomac Two Step

One of the challenges in driving into DC each morning from the Virginia side is doing the Potomac two step over the bridges. Memorial and Key Bridges all have similar dynamics to that of the Roosevelt Bridge. For inbound traffic the Roosevelt is four lanes wide. From the west comes two lanes from I-66. Just before the bridge an on ramp brings a stream of cars with many of them in less than .2 miles seek to move to the left lane while about a quarter of those cars coming down I-66 cross from left to right and off a ramp that starts just past the on-ramp…oh and some cars coming down the on-ramp keep going without merging so that they can take the off-ramp toward the Pentagon.

Just as the two lanes enter the bridge a third lane on the left opens. It is just past this point that a stream of cars enter the bridge and a fourth lane from the right. At the end of the bridge are four different directions, one on the far left going down onto the Potamic River Freeway, the second from the left going of to a ramp toward the State Department, the next lane is second from the right dumps directly into Constitution Avenue, while cars on the last lane, which is on the far right, go either onto Constitution off another road that takes them to Independence Avenue.

In a less than a quarter of a mile cars maneuver from the far right to the far left while others move in the other way. About half the cars move from the far right to the far left or from the far left to the far right. Only about a quarter of the cars remain in their entry lane. The same type of crossing maneuvers by a nearly hundred of cars every minute takes place on every day on the Roosevelt and Memorial Bridges. The same process is repeated during the evening on all three bridges.

Three weeks ago it dawned upon me that in six years I have only known of one accident on any of the three bridges. Drivers are aware of all the crossing and are prepared to allow other drivers to merge or to cross in front of them on the way to the next lane. Unfortunately the same courtesy is not found at the same rate elsewhere in the area.