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Saturday, February 8, 2014

Conflicted Crosswalks: Gun Hill Road and Webster Avenue

This is the first of a series of posts about crosswalks with conflicts that threaten pedestrians. These are intersections located in neighborhoods that are not living up to their full potential, due in large part to traffic that is hostile to walking. As they exist today, these street corners are not neighborhood places; they are merely the residual space where flows of vehicular traffic collide. Each intersection has its own unique problems, but looking at several cases will help to identify some commonalities. The first intersection we will review is Gun Hill Road and Webster Avenue in The Bronx.

This is an intersection that periodically injures pedestrians, sometimes fatally. Taken as an absolute number, the accidents are on the high side but may not stand out as a priority. However, after considering that the total pedestrian activity is quite low, it becomes apparent that the actual crash rate is particularly high and clearly indicates a problem. (A deeper review would indicate that the unsafe intersection is a major factor in suppressing pedestrian volumes, as people avoid the intersection and trips between the neighborhoods altogether for fear of being hit by a car!) Pedestrians crossing Webster Avenue on either the north or the south side encounters real problems with left-turning vehicles.

On the south side of the intersection, westbound vehicles on Gun Hill Road have a dedicated green turn phase at the beginning of the cycle. Pedestrians are supposed to wait, and they have a signal light with the do-not-walk hand. Nevertheless, habituated to crossing when the light changes, many of them enter the intersection against the light, sometimes right into the path of the turning vehicles. Closely observing the behavior of the pedestrians that wait for the walk signal, however, suggests that some of the illegal crossings may be deliberate, and not as foolish as they initially appear. After the dedicated green phase expires, traffic going through in the opposite direction gets a green and pedestrians have a concurrent walk signal. The issue is the permissive green and the left-turning vehicles accelerating through gaps in the oncoming traffic, and then cutting through the crosswalk. At least when the pedestrians cross in front of the left-turning vehicles during their dedicated turning phase, they are the only conflicting movement demanding the drivers' attention. When they cross legally, the conflicting drivers are forced to split their attention between cars coming down a hill at 30 mph and pedestrians that may be entering the intersection from either corner. Basic self-preservation will tend to fixate the drivers' attention on the threat of the oncoming traffic, rather than the vulnerable pedestrians.

Likewise, on the north side, pedestrians initially have a no crossing signal, despite the fact there are no conflicting left turning vehicles. During this phase, the only conflicting movement is a light volume of right-turning vehicles, which are starting from a stop and have a good view of the pedestrians. Despite these favorable conditions, the traffic control signals only allow the pedestrians to legally cross the intersection when eastbound vehicles are allowed to turn left across their crosswalk and right-turning vehicles begin arriving at the intersection in motion. This is particularly problematic.

The New York City Department of Transportation has actually studied this intersection as part of the Gun Hill Road Congested Corridors Study, but the pedestrian conflicts have not been resolved. It would be inaccurate and unfair to say DOT staff were unsympathetic, but with limited resources and a different primary study purpose, this issue never became a focus. Perhaps with the new Vision Zero goals this intersection can get another look.

This may require a change in signalization methods at DOT, though. DOT's current theory for cases like this is that providing the walk signal on one side of the intersection would encourage the pedestrians on the other side, who have a do-not-walk signal due to the conflict turn, to cross at the same time. I appreciate the concern, but every aspect of my observations suggests this is the wrong approach.

Let's start with a comparison of observed behavior and the specific problem they are trying to avoid: pedestrians on the south side of the intersection crossing during the left-turn phase. Already the level of compliance approaches zero. So providing a safer legal crossing opportunity on the north crosswalk apparently would not have the feared effect of undermining the safety of the south crosswalk.

Beyond this site-specific consideration, I believe the current approach for these pedestrians signals undermines pedestrian compliance overall. After pedestrians routinely encounter intersection where they find they are prohibited from crossing during the periods that are actually safest for them, I expect they develop a general disregard for the signals. When their experience is that complying with signals could put them in jeopardy, the only purpose for observing them would be to avoid overzealous police officers who might ticket them for jaywalking. Consistently aligning pedestrian signals with the needs of each crosswalk could eventually make pedestrians more likely to trust and obey the traffic controls.

So far we have not really addressed the south crosswalk, though. The crossing with the dedicated left turn phase is the particularly challenging location. Ideally, the turning vehicles would simply be held until after the pedestrian crossing phase with the through movements. There are two considerations: 1) the loss of capacity for the turn approach with the removal of the permissive green, and 2) the storage space necessary for the left-turning vehicles.

Although DOT staff have raised the issue that the permissive green allows a few more vehicles to sneak through, I think it's a non-issue. The permissive turn currently steals a little green time from other movements that could be reallocated. Removing the friction of turning vehicles imposed by the permissive green could allow for a small reallocation of time from the through movements to the turning phase. Additionally, the permissive green results in turning vehicles camping out in the intersection and then clearing after the light has turned red, syphoning off a little of the effective green time from Webster Avenue. Finally, it should be noted that at the beginning of the cycle, the left turn loses some of its effective capacity due to the friction with the pedestrians crossing illegally, which would be reduced if the pedestrians were allowed to start crossing earlier.

I suspect the issue of storage capacity could prove to be a real obstacle. Given the gridlocked conditions that result with the turns on and off the Bronx River Parkway in the space between Webster Avenue and White Plains Road, it simply may not be possible to hold a queue of left-turning vehicles. A careful review should be undertaken to determine if this concern would prevent the improvement of retiming the left turn to the end of the phase.

If it is not possible to move the left turn to the end, the permissive green should be eliminated. After the left turn phase, left turns should be prohibited. This would allow pedestrians who wait for their walk signal to cross much more safely by removing the harried left turn across oncoming traffic that sends cars speeding across the crosswalk. As discussed above, any loss of capacity from removing the permissive green can probably be addressed by adding the signal timing effectively gained from the other approaches back to the left turn.

I don't mean to suggest these are simple fixes. There is a chance some of these suggestions may not even work. Given the terrible conditions that currently exist, though, it is well past time to undertake a serious study of the potential for these or other potential improvements to reduce the threat to the pedestrians simply trying to get across the street while they have the light. Even modest improvements in walking conditions would go a long way toward breaking down the barrier between Norwood and White Plains Road.

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