The 13B Metrobus line has been making an extra loop after the Pennsylvania Avenue bike lane forbade left turns onto 10th Street, WMATA officials said.

The bus, which runs a counterclockwise loop between the Pentagon, the Federal Triangle, and Arlington Cemetery, currently uses Pennsylvania Avenue westbound between 6th and 10th Streets, NW, where it turns left on 10th. The block between Pennsylvania and Constitution on 10th serves as a good layover area for many buses including the 13B.

Once the bike lanes went into effect, traffic was no longer permitted to turn left on 10th. Instead, the 13Bs have been continuing on Pennsylvania Avenue to 12th Street and making a small loop on 12th, E, and 11th to get back to Pennsylvania pointing the other direction where they can make the turn, according to bus planner Jim Hamre.

13A (blue) and 13B (purple). 13B detour is in light purple. Base image from NextBus.

WMATA has asked DDOT to grant buses an exception to the left turn restriction. DDOT will have to weigh the value of moving buses efficiently versus the potential danger to cyclists. Bus exceptions to left turn rules do exist elsewhere.

But is this the most efficient routing for the bus? Last week, we printed a letter from reader Tom Leonard wondering why the P1 bus detours away from its most direct route to service this same area of Pennsylvania Avenue. The P1 takes Pennsylvania in the opposite direction, eastbound between 10th and 7th, and uses Constitution instead westbound.

WMATA bus planner David Erion explained that that detour provides a common transfer point between various P routes. But is that worth the extra detour? Each diversion benefits some riders and inconveniences others.

The 13B loops counterclockwise around the FTC, Archives, and DOJ. Meanwhile, the 13A, which runs the loop around the Mall and Potomac in the other direction, instead goes north on 12th, east on Pennsylvania, and south on 10th, looping around the Old Post Office and the IRS. 13A riders who want to go to Archives, for example, access it from the Constitution Avenue side instead of the Pennsylvania Avenue side.

What about putting the 13A and 13B on the same route in the Federal Triangle area? Riders going to restaurants and theaters on 7th Street would have to walk one extra block if they’re using the 13B, but would then have stops in the same places for the 13A and 13B. And DDOT wouldn’t have to grant an exception.

Hamre also noted that the south side of Pennsylvania is very crowded with buses today, including the 13B as well as the 30s, 63/64, D1 and more. The more buses stop on a block face, the more often they delay each other. For this reason, the bus planners try to spread buses out between different streets in busy areas like downtown DC.

On the other hand, this makes the bus map extremely confusing and hard to remember beyond simply the one bus someone takes each day. It also means that riders who could choose between two different routes can’t wait on a single street and take whichever bus shows up first.

It would make a certain sense to have major “bus streets,” perhaps with dedicated lanes, that group as many buses as possible onto the same streets. But if the WMATA bus planners are right, at the very least DC would need a number of these downtown because there simply isn’t enough room on a few streets for all the buses.

The bus planning also does try to get buses as close to as many riders as possible. It’s always a tricky tradeoff between simpler and faster routes and minimizing the walking riders have to do. I’d move the balance a bit toward simplicity, but any change would surely hurt some riders, including many for whom walking an extra block or two isn’t as easy as it is for some of us.