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Thread: Interesting Piece About Infrastructure and Pass Distances

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    Default Interesting Piece About Infrastructure and Pass Distances


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    This is obvious to anyone who has ridden the Gallows Road bike lanes and been passed by a Fairfax Connector bus.

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    The study results are consistent with my own perceptions as a rider.

    In the USA, many of our bicycle lanes are built in the door-zone, so one needs to hug the left edge of the lane to use them. Which of course invites closer passing by any motorists in the adjacent lane who fail to alter their own courses to give proper clearance. On the other hand, where there are no bicycle facilities and a cyclist is claiming an entire full-width travel lane, motorists must change lanes to pass. Most drivers change lanes entirely and in so doing allow far more clearance than required.

    I would like to see a deeper investigation of how passing distance depends on cyclist position relative to the painted lines. Is this entirely explainable by rider positioning relative to the lane lines drawn for vehicles? Or is there further association between the existence of a bike lane and closer passing, even after controlling for cyclist position?

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    Yep, I've been saying this for a while. There are rare circumstances where I'll push hard for painted bike lanes.

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    My sense is that while many drivers will drive close to the edge of the bike lane (which will be too close if I am riding on the left of it to avoid potential dooring) they will also generally not ride into the bike lane. When I am riding without a bike lane, whether taking the lane, or riding to the right (because its a segment where for whatever reason I am not comfortable taking the lane) the variance seems greater - some cautious drivers will pull far over, and some will pass way to close, including "punishment passes" That is why given a route choice, I will often pick a door zone bike lane route over a route with no infrastructure. Some of it will depend on what I know about parking turnover on the route. East Glebe near Commonwealth in Alexandria, is not like SB Crystal Drive in Arlington, for example. Also depends on the no infra route - some two ways have no center stripe, encouraging drivers to pull over to pass. Where there is a center stripe, and high volume in both directions (but only one lane in each direction) drivers are, I find, less likely to pull over far enough. Some one ways have sufficient bike volumes that drivers are aware and relatively patient (Abingdon in Fairlington) others, not so much.

    Also of course many door zone painted bike lanes are put in for traffic calming (wide lanes can lead to higher speeds) and if that succeeds, it can make it a more desirable route.

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    Quote Originally Posted by lordofthemark View Post
    That is why given a route choice, I will often pick a door zone bike lane route over a route with no infrastructure.
    Interesting. While I certainly do get the occasional close pass while claiming a lane, I experience far more of them when using a DZBL. Perhaps we position ourselves differently in such a lane? Do you tend to ride in the door zone, in the center of the lane, or near the left edge? I try to keep at least four feet away from any parked car, which might put me closer to the adjacent lane than other riders. (But I will make an exception to filter through a DZBL slowly to bypass congestion).

    On some streets I also might alternate between the left edge of the DZBL and claiming the adjacent lane. Basically merging left anytime I see a squeeze point ahead, and merging right to facilitate vehicles passing whenever I encounter a sufficiently long stretch where the bike lane appears safer (due either to a lack of parked cars, or at least none that are encroaching over the lines)

    As you have indicated, there is no simple approach that can optimize safety in all scenarios, because there are a multitude of factors that come into play when assessing the relative dangers from passing motorists vs. parked cars. Such as: expected parking turnover, the presence of a center line or median, vehicle speeds, how far drivers are typically going before parking or turning off the street, etc.

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    Quote Originally Posted by scoot View Post
    Interesting. While I certainly do get the occasional close pass while claiming a lane, I experience far more of them when using a DZBL. Perhaps we position ourselves differently in such a lane? Do you tend to ride in the door zone, in the center of the lane, or near the left edge? I try to keep at least four feet away from any parked car, which might put me closer to the adjacent lane than other riders. (But I will make an exception to filter through a DZBL slowly to bypass congestion).

    On some streets I also might alternate between the left edge of the DZBL and claiming the adjacent lane. Basically merging left anytime I see a squeeze point ahead, and merging right to facilitate vehicles passing whenever I encounter a sufficiently long stretch where the bike lane appears safer (due either to a lack of parked cars, or at least none that are encroaching over the lines)

    As you have indicated, there is no simple approach that can optimize safety in all scenarios, because there are a multitude of factors that come into play when assessing the relative dangers from passing motorists vs. parked cars. Such as: expected parking turnover, the presence of a center line or median, vehicle speeds, how far drivers are typically going before parking or turning off the street, etc.
    I also modify my riding based on the context, sometimes taking the lane, etc.
    However, scoot and I and most of us on this forum are outliers. The vast majority of people who do not now ride a bike will not start riding if that is the kind of infrastructure that is provided to them. They will only start riding when they have infrastructure that makes them feel safe on their entire journey.

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    Quote Originally Posted by lordofthemark View Post
    My sense is that while many drivers will drive close to the edge of the bike lane (which will be too close if I am riding on the left of it to avoid potential dooring) they will also generally not ride into the bike lane.
    I feel like drivers out in the suburbs are always in the bike lanes, frequently cutting corners through the bike lanes, or using them as long extensions of turning lanes. Gallows is particularly bad for corner-cutting: you can see several curves where the paint for the bike lane has worn down from all the car traffic that drives on it. Hilltop Rd between Old Lee Hwy and Cedar Lane recently had one travel lane replaced by a bike lane, and I routinely see cars driving through that bike lane as if the change never happened. That one in particular blows my mind.

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    Quote Originally Posted by scoot View Post
    Interesting. While I certainly do get the occasional close pass while claiming a lane, I experience far more of them when using a DZBL. Perhaps we position ourselves differently in such a lane? Do you tend to ride in the door zone, in the center of the lane, or near the left edge? I try to keep at least four feet away from any parked car, which might put me closer to the adjacent lane than other riders. (But I will make an exception to filter through a DZBL slowly to bypass congestion).

    On some streets I also might alternate between the left edge of the DZBL and claiming the adjacent lane. Basically merging left anytime I see a squeeze point ahead, and merging right to facilitate vehicles passing whenever I encounter a sufficiently long stretch where the bike lane appears safer (due either to a lack of parked cars, or at least none that are encroaching over the lines)

    As you have indicated, there is no simple approach that can optimize safety in all scenarios, because there are a multitude of factors that come into play when assessing the relative dangers from passing motorists vs. parked cars. Such as: expected parking turnover, the presence of a center line or median, vehicle speeds, how far drivers are typically going before parking or turning off the street, etc.
    My position in the bike lane will vary. Sometimes of course the parking spaces are empty, in which case I will often ride on the right edge of the bike lane. If I its a time and place where I think someone is actually going to open a door, or even begin to pull out of a space unsafely and without warning, I will ride the left edge of the bike lane. More often I ride to the left of the center of the bike lane but not right on the left edge.

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    Quote Originally Posted by dkel View Post
    I feel like drivers out in the suburbs are always in the bike lanes, frequently cutting corners through the bike lanes, or using them as long extensions of turning lanes. Gallows is particularly bad for corner-cutting: you can see several curves where the paint for the bike lane has worn down from all the car traffic that drives on it. Hilltop Rd between Old Lee Hwy and Cedar Lane recently had one travel lane replaced by a bike lane, and I routinely see cars driving through that bike lane as if the change never happened. That one in particular blows my mind.
    The lanes on Gallows are pretty bad (I note though those are not door zone bike lanes).

    I am thinking more of places like Eye Street SE-SW in DC, 4th Street SE in DC, Commonwealth in Alexandria, North Hampton in Alexandria, Cameron and Prince in Alexandria.

    There are also of course a few places (in Arlington Vietch or was it Quincy?) where there is a very wide door zone bike lane, with the striping used to encourage riders to ride away from the door zone. That seems like progress. Narrow door zone bike lanes, on streets with high parking turnover are not usually implemented any more in DC, Arlington or Alexandria, I think though I have seen some new ones like that in other regions.

    IMO the worst in our region, at least that I usually experience, is SB Crystal Drive. That is one place where I will take the lane even though there is a bike lane. The parking turnover is too high. Maybe 14th St NW in DC is as bad?

    I do not think we should wait to for someone to be killed before declaring something dangerous, of course, but I do note that I once asked Washcycle if there were any records of a dooring fatal in a bike lane in this region - he found none as far back as he had records (to 2002?) That may be because there were until recently too few bike lanes to be statistically meaningful. Or it may be because motorists who see a painted bike lane, are more conscious of checking for a passing cyclist before opening a car door. Or it may be purely a critical mass effect - DZBLs are placed in places where more people ride, or attract riders. I don't know. I don't think the possibility that the painted bike lane changes driver door opening behavior can be ruled out though. Now if you are going take the lane as an alternative, then you can avoid dooring anyway.

    But I regularly see riders riding in the door zone on streets with no infra. I have even seen that on streets with properly painted (IE in the center of the lane) sharrows. Its not impossible that for those riders, DZBLs actually reduce dooring danger - because they would ride in the door zone anyway, and drivers would be less likely to expect bikes absent a door zone bike lane. Note I am not suggesting implementation of door zone bike lanes on quiet streets where removal of a center stripe is a viable option. But given all kinds of bad infra in the region - from PBLs with issues (like L and M) to sharrows painted in the door zone or in the parking lane (Valley Drive in Alexandria) to high speed arterials with no infra, I can't get as excited about the evils of DZBLs as some do. I am very reluctant to push for their removal in favor of no infra anywhere (as opposed to pushing to replace them with PBLs) and I don't want to remove them from the set of options for traffic calming.

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