The intersection of Lee Highway and Lynn Street in Rosslyn, where the Custis Trail crosses Lynn St., is one of the most dangerous intersections for cyclists in the Greater Washington area.  By reconfiguring the exit ramp for the Key Bridge, this conflict could be reduced, dramatically improving safety while also potentially improving traffic flow.


Graphic by the author.



This intersection has received a lot of scrutiny lately, after a driver sideswiped a cyclist who was subsequently blamed for the incident by Arlington Police.

The primary problem at this intersection is traffic turning right from the I-66 off-ramp onto Lynn Street to head toward the Key Bridge. This traffic has a green light at the same time as the pedestrians and cyclists have the walk signal.  There are two lanes of right turning cars (and sometimes cars in the third lane turn right illegally).  Shifting the Key Bridge traffic to the north of the Custis Trail crossing could eliminate this conflict.

According to recent counts, the intersection sees more than 400 bikes an hour during rush hours, and that number is increasing. That is one bike about every 9 seconds on average. 

My proposed redesign could significantly improve the situation for all users: cyclists, pedestrians and drivers. The numbers below correspond to the red numerals on the above graphic.

1. Split I-66 offramp: Currently the I-66 exit ramp is one lane that curves up to Lynn Street, dividing into three lanes as it approaches Lynn. The right lane is right-turn only, the middle lane is right turn or straight onto Lee Highway, and the left lane is straight only.

My proposed configuration would divide the ramp just after its split from I-66. Lee Highway traffic would follow the existing ramp up to the light at Lynn Street. Traffic headed for the Key Bridge would curve down under the existing Custis Trail ped/bike bridge over the GW parkway and then curve left to join the existing Key Bridge ramp from the southbound Parkway.

2. Reconfigure southbound offramp intersection: The combined Key Bridge ramps could be reconfigured into a 90-degree intersection at Lynn Street with a traffic light. While I proposed all three lanes to be right turn only, the far left lane could potentially allow movement onto the ramp for the northbound GW Parkway. This intersection would have no-right-turn-on-red restriction, which would eliminate the current conflict for cyclists and pedestrians also headed for the Key Bridge.

Cyclists and pedestrians could cross with the Lynn Street traffic while it has the green, and would wait with the Lynn St. traffic while the ramp traffic has the green. With three right turn lanes and no time lost yielding to bikes and peds, there could easily be an increase in capacity for cars, even with right turns on red prohibited. In evening hours, right-on-red movements could be allowed from the right-most lane only.

3. Narrow existing Lynn/Lee offramp: The existing ramp/Lynn St. intersection can then be narrowed to two lanes, allowing more space for the trail, improving sight lines, and reducing crossing distances. Both lanes would be straight only onto Lee Highway. This would completely eliminate all conflicts with Custis Trail traffic, since there would be no turning cars. Lee Highway and Custis Trail traffic would cross on the green and would wait on the red while Lynn Street traffic proceeded.

It appears that there is probably enough room under the existing bike/ped bridge to accommodate a new ramp lane without lengthening the bridge.  This Google Street View shows the southbound lanes of the parkway traveling under the pedestrian bridge. 


Image from Google Street View.


Note there is space on both sides of the lanes (the far support is about six feet beyond the stone wall if that additional space were needed.)  The new configuration would have one lane of traffic traveling north as it passes under the bridge in addition to the Parkway lanes, which would be shifted into the existing median. 

I paced it off, and my best estimate is 58 feet of span available between the support wall on the west and the support column in the median of the Parkway.  That would accommodate three 12’ lanes with 22 feet for shoulders and median. I’m not an engineer, but if that is possible, then this solution allows for eliminating the conflict without the need for significant additional infrastructure like a bike tunnel.

While this may seem like a costly proposal, a permanent solution like this one is eventually going to be necessary. The conflict at this intersection can only get worse. Bicycle use is increasing rapidly, and both DC and Arlington are promoting more cycling and investing in it with Capital Bikeshare and other efforts. As bike traffic increases, the number of conflicts with right turning cars will no doubt increase with it.

The redesign also would nicely complement the N. Lynn St Esplanade and Lee Highway/Custis Trail improvement projects that are currently being planned.  A meeting on these projects is scheduled for tomorrow night.

Whatever the solution, the northern portion of Rosslyn will need major updates to its traffic patterns in order to accommodate a growing number of cyclists and pedestrians in an environment that was originally designed for the convenience of motorists.