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Thread: Interesting Piece About Infrastructure and Pass Distances

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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.
    One option is to put in flexposts right where the corner cutting is most a problem - there is something like that in the new bike lane (not door zone) on SB 7th St SW near the Wharf. You would do that in a place where for some reason you cannot flexpost protect the entire bike lane.

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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. 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.
    I'm the opposite and avoid door zone bike lanes as much as possible. I'd rather ride in traffic and force cars to go around then try to look into every parked car to be sure no one is going to door me.

    I get the traffic calming reasons, but there's got to be a better use of the space than a narrow, unsafe bike lane. East Glebe is one of the worst bike lanes I've seen built recently and should never been built with the idea of it being a bike lane. It would be better to use the space to expand the sidewalks, maybe even to the point they would be wide enough (8-10') to be shared-use paths that lower speed cyclists could safely use.

  3. #13
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    Quote Originally Posted by zsionakides View Post
    I'm the opposite and avoid door zone bike lanes as much as possible. I'd rather ride in traffic and force cars to go around then try to look into every parked car to be sure no one is going to door me.

    I get the traffic calming reasons, but there's got to be a better use of the space than a narrow, unsafe bike lane. East Glebe is one of the worst bike lanes I've seen built recently and should never been built with the idea of it being a bike lane. It would be better to use the space to expand the sidewalks, maybe even to the point they would be wide enough (8-10') to be shared-use paths that lower speed cyclists could safely use.

    Expanding the sidewalks is expensive, especially as it typically involves rebuilding the drainage.

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    I did some quick googling and found a guy opposing current standards that allow too narrow DZBLs, talking about lack of good reporting of dooring incidents, etc. Definitely an anti-DZBL guy.

    And this is what he found in SUPPORT of sharrows instead.

    In the most successful case, 85 percent of bicyclists were riding within the door zone before SLM installation, and only 45 percent after.


    AFTER putting in sharrows, 45% of riders were STILL riding in the door zone. Even I did not think it was that high.

    People on forums like this, who both know a lot about dooring and VC, are more comfortable in traffic, and are faster (which makes taking the lane more comfortable (and I think safer, but I don't think everyone agrees)) and makes door zone riding more dangerous (yes I know there are dooring risks at any speed) are going to take the lane even without sharrows, and tend to think sharrows will eliminate door zone riding. I don't think that is the reality for newbie/occasional riders/interested but concerned.
    Last edited by lordofthemark; 04-12-2019 at 09:24 AM.

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    Here is a street view of a decent implementation in Rockville, MD of a 2-Way Cycletrack with parked cars that's more comfortable than DZBL. Cars are parked the "opposite way" of a normal bike lane, so it's easier to watch for opening doors, and less injury when colliding. Now if one-way PBL go the opposite way, we get the same thing, but requires design changes at intersections, to make sure that cyclists follow the proper direction.
    Last edited by n18; 04-12-2019 at 11:15 AM.

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    Quote Originally Posted by lordofthemark View Post
    I did some quick googling and found a guy opposing current standards that allow too narrow DZBLs, talking about lack of good reporting of dooring incidents, etc. Definitely an anti-DZBL guy.
    By googling your quote, I assume that you found this article.

    Quote Originally Posted by lordofthemark View Post
    In the most successful case, 85 percent of bicyclists were riding within the door zone before SLM installation, and only 45 percent after.
    AFTER putting in sharrows, 45% of riders were STILL riding in the door zone. Even I did not think it was that high.
    It seems plausible to me. I have taken numerous rides with less experienced cyclists and have observed many of them riding in door zones, even on low-speed streets with properly located sharrows or without markings at all.

    On one hand, a drop from 85% to 45% sounds like an enormous improvement. It suggests that just a little bit of paint could sharply cut doorings on those streets. But it also sounds like that one data point was his "best" out of four separate studies, so should be consumed along with a huge grain of salt. The article itself is behind the Elsevier paywall.

    Quote Originally Posted by lordofthemark View Post
    People on forums like this, who both know a lot about dooring and VC, ... tend to think sharrows will eliminate door zone riding.
    I can't imagine anyone believing that sharrows could ever eliminate door zone riding.

    I do believe that properly located sharrows can help reduce door-zone riding and by extension dooring incidents. I also believe that riders who feel safer in a travel lane than a door zone are likely to experience more motorist harassment where DZBLs are painted than they would if sharrows were painted instead. (I have no data to support the latter hypothesis, just my perception of anecdotes from my own experience.)
    Last edited by scoot; 04-12-2019 at 01:28 PM.

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    "I have taken numerous rides with less experienced cyclists and have observed many of them riding in door zones"

    I sometimes do a weekend ride with a well-known local shop. Road cyclists, some of whom race. I see some of them riding in the door zone fairly consistently through Alexandria and Arlington streets without bike lanes.

    People, even those with experience, sometimes just aren't very good at assessing the accretion of risk. (I suppose I'm not either or I'd commute some other way.)

  8. #18
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    Quote Originally Posted by scoot View Post
    By googling your quote, I assume that you found this article.



    It seems plausible to me. I have taken numerous rides with less experienced cyclists and have observed many of them riding in door zones, even on low-speed streets with properly located sharrows or without markings at all.

    On one hand, a drop from 85% to 45% sounds like an enormous improvement. It suggests that just a little bit of paint could sharply cut doorings on those streets. But it also sounds like that one data point was his "best" out of four separate studies, so should be consumed along with a huge grain of salt. The article itself is behind the Elsevier paywall.



    I can't imagine anyone believing that sharrows could ever eliminate door zone riding.

    I do believe that properly located sharrows can help reduce door-zone riding and by extension dooring incidents. I also believe that riders who feel safer in a travel lane than a door zone are likely to experience more motorist harassment where DZBLs are painted than they would if sharrows were painted instead. (I have no data to support the latter hypothesis, just my perception of anecdotes from my own experience.)

    To clarify, I agree that 85% to 45% is a net benefit. In places where there is no segregated infra possible, I do support correctly placed sharrows. I also support them in those places where the contraindications for DZBLs are strongest (and a PBL is not possible). IF a painted DZBL impacts driver door opening behavior (I have no data for that (beyond the absence of fatalities which is not strong evidence) either, but seems intuitively likely to me) it MAY offset the benefit of sharrows reducing door zone riding - and again, the presence of DZBLs may have other benefits in terms of reduced rear end collisions (not zero) traffic calming, etc.
    Last edited by lordofthemark; 04-12-2019 at 01:49 PM.

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    Quote Originally Posted by scoot View Post
    I can't imagine anyone believing that sharrows could ever eliminate door zone riding.

    I do believe that properly located sharrows can help reduce door-zone riding and by extension dooring incidents. I also believe that riders who feel safer in a travel lane than a door zone are likely to experience more motorist harassment where DZBLs are painted than they would if sharrows were painted instead. (I have no data to support the latter hypothesis, just my perception of anecdotes from my own experience.)
    This is why I would prefer sharrows be painted instead of DZBLs if we're not going to install PBLs or cycle tracks. There are some examples of painted bike lanes overseas where the driving area is narrowed to provide wide enough painted bike lanes, but that's not what's been installed here. Sharrows, while not good on higher speed roads, are better than narrow DZBLs and guide cyclists where to appropriately position themselves in the lane for safety.

  10. #20
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    Another issue with sharrows and the VC approach generally, is scaleability. Sharrows "work" today, because there are not that many people on bikes and those who pick a route without seg infra are more likely to be faster riders. Imagine that instead of 2% mode share (5% in the District I guess) we had 10 to 20% mode share - but still lots of motor vehicle traffic. And that a large proportion of that 20% were children, elderly, people pulling trailers, etc. The conflicts with motor vehicle traffic would create issues - in some places worse than the conflicts created by seg infra.

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