Improving a Cambridge Crosswalk

March 30, 2013

Biking across Cambridge remains problematic despite their various efforts to improve things. The least-challenging routes are nowhere near direct, and the more direct routes contain uncomfortable stretches and a few random dangers. Sometimes fixing trouble spots is hard — for example, there has to be a tradeoff between car flow and bicycle flow, or between parking and bicycle flow.

But sometimes, making things better for bicycles requires no tradeoff. An example of this is the crosswalk from Cambridge Common to Harvard Law School across Mass Ave. Technically it’s “not for bicyles”, but in practice it is, because the other routes through Harvard Square are crowded and full of cars.

This crosswalk has two problems. First, it’s not big enough; there’s often enough pedestrian and bicycle traffic that people pile up and get in each other’s way. This can lead to conflict between bikes and peds, which is not good. Second, it’s not intuitive. For whatever reason, the crosswalk is divided into segments that don’t all “go” at the same time. A cyclist who’s not aware of this (who makes the completely reasonable assumption that it’s all go) runs the risk of sprinting right into the front of a car with a green light.

The problematic lane is marked with a pink dashed line. The other lines, pink and blue, show (what could be) the two basic cycles for this light.

My solution to this problem comes in two parts. First, the pedestrian crossing must be all “go” at the same time. The light then has two cycles, pink and blue. One problem with this is that it requires a very long walk signal for the slowest pedestrians to get all the way across, and this will probably interfere with the car traffic flow. Instead, run the walk signal on a shorter cycle that only gives the slowest walkers time to get half-way across. However, at the island where they are expected to stop and wait, provide a nice place to wait (shown in the picture with a green box). That means covered to protect from the weather, and with substantial barriers to protect from passing traffic (in the case of parents with small children, to help keep children getting into traffic). This should include a bench, so people can sit and rest.

Second, because the faster pedestrians and cyclists will certainly plan to cross in a single cycle, make the crossing wide enough (and mark it) so that they can spread out, move fast, and avoid conflict. There’s no particular reason that the crosswalk needs to be as narrow as it is; there is an ample stretch of unused space, and it should be dedicated to making this crossing nicer for people who aren’t driving.

All the crosswalk signals must have countdown timers, so that people crossing can properly estimate whether they can make it across in a single cycle or not.

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