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Correct. Anyone that says roundabouts are less safe doesn't have science backing their claim. While, they do not reduce the number of accidents and in some case

by Clent 3y ago

Correct. Anyone that says roundabouts are less safe doesn't have science backing their claim. While, they do not reduce the number of accidents and in some cases can increase accidents, but they consistently reduce the severity of the accidents. A three lane roundabout may be annoying when encounter as a tourist but the majority of locals going about their daily commutes quickly master them. For a three lane roundabout the inner lane is left turn only. The inner lane is left turn or straight and the right lane is right turns only. The ones in my area have ample signage indicating which lane allows for each type of turn.

mikepurvis 3y ago
I would argue that the safety stats for them are still excessively car-centric. That is to say, roundabout collisions have better outcomes for car occupants specifically because they turn crashes into the kinds of crashes that cars handle best, which is low speed rear-endings, with the crumple zones doing all the heavy lifting to protect occupants. I’m much more skeptical about how roundabout users fare when they are people walking or riding bicycles. At least in my city, we've had roundabouts for years, and the yield rate for pedestrians is ghastly— like, sub-50% of drivers stopping for someone waiting to cross and remaining fully stopped until the person is completely off the roadway. In theory this is a fine of hundreds of dollars ("failure to yield to crosswalk"), but it appears to receive basically zero enforcement in practice. As a result, the fancy multi use paths that accompanied our roundabout installations get little use, since it's obvious to anyone who tries them how dangerous and unprotected they are.
- pmontra 3y ago
  I'm both a car driver and a cyclist. There are a zillion roundabouts in the country I'm living in. This is my experience and I'd like to hear a traffic designer about it. Roundabouts feel safer than a 4 way intersecting when I'm in a car even if it's annoying to have to slow down and accelerate again when there is very little or no traffic, which is normal in the countryside. It also consumes more fuel, wears the car, adds to pollution. It's different when I'm riding my bicycle. Roundabouts put me closer to cars, especially if there are traffic dividers that force cars closer to the side of the road. Then cars are usually slower than a bicycle in a small or medium sized roundabout (think of race bicycles with drop bars,) which adds up to chances of being packed between two cars. My feeling is that what's good for cars is bad for bicycles. As a cyclist I can see what's around me much better than when I'm in my car. Intersections don't feel like a problem because of the extra visibility. When I'm riding I long for old times straight roads, with a line on the side and half a meter of asphalt on the other side to ride on. No roundabouts, no speed bumps especially the 3M style plastic ones, which I can jump but they are annoying. All those safety devices, including roundabouts, increase fatigue and danger. They are also the main reason for crashes in bicycle races but that's not an issue for normal people. Finally, as I both drive and ride I know how to behave not to put in danger the cyclist. When I drive I don't overtake bicycles before a roundabout because they'll be at least as fast as me. I don't overtake when there is a short traffic divider which narrows the road. A long one, oh well, I have to. Same thing when I approach an intersection where I have to yield or stop. Bicycles will be definitely faster there because they can look around better than me and decide what to do quickly. When I ride and I'm approaching a roundabout or entering a short narrowing of the road I look behind me and if it's safe I lean a little to the center of the road to prevent cars to overtake when they'll be forced to come close to me.
  - axiolite 3y ago
    Your observations are quite apt. "Researchers in Belgium found that single lane roundabouts without a protected bike lane increased crashes by 93%, while Danish researchers said roundabouts that did have separated lanes saw an 84% reduction in crashes." CNBC: Roundabouts Are Safer. So Why Does The U.S. Have So Few Of Them? https://www.youtube.com/watch?v=atORPw-w83I https://www.youtube.com/watch?v=atORPw-w83I
  - usrusr 3y ago
    Ah, those traffic dividers, clearly designed by people assuming that all roads should be limited access... "All those safety devices, including roundabouts, increase fatigue and danger." They literally distract from the traffic when you aren't in a little isolated house on wheels where people are prone to forget that traffic even exists. All those things designed to help getting a driver's eyes off WhatsApp require cyclists to get their eyes away from traffic. On the topic of roundabouts, one thing I rarely see discussed (never?) is that traffic lights conveniently compress the vehicle stream into packets of high and low intensity, greatly helping smaller intersections downstream. Roundabouts on the other hand flatten the vehicle frequency and of there's a difficult place to enter or cross the stream, even a modest amount of traffic can be too much. In the end everything that isn't a roundabout can only be navigated by relying on someone in the dominant stream showing off compassion with those waiting. This makes everything go even slower and you quickly end up with even dominant streams going less than walking speeds. I have a hypothesis that roundabout-dominated road graphs are particularly prone to effective throughput dropping once a certain threshold of throughput demand is reached. Traffic light dominated graphs are immune to this if drivers are just a little careful to not enter an intersection before they can assume that they will be able to leave before the lights change.

by Clent 3y ago

mikepurvis 3y ago

I would argue that the safety stats for them are still excessively car-centric. That is to say, roundabout collisions have better outcomes for car occupants specifically because they turn crashes into the kinds of crashes that cars handle best, which is low speed rear-endings, with the crumple zones doing all the heavy lifting to protect occupants. I’m much more skeptical about how roundabout users fare when they are people walking or riding bicycles. At least in my city, we've had roundabouts for years, and the yield rate for pedestrians is ghastly— like, sub-50% of drivers stopping for someone waiting to cross and remaining fully stopped until the person is completely off the roadway. In theory this is a fine of hundreds of dollars ("failure to yield to crosswalk"), but it appears to receive basically zero enforcement in practice. As a result, the fancy multi use paths that accompanied our roundabout installations get little use, since it's obvious to anyone who tries them how dangerous and unprotected they are.

pmontra 3y ago
I'm both a car driver and a cyclist. There are a zillion roundabouts in the country I'm living in. This is my experience and I'd like to hear a traffic designer about it. Roundabouts feel safer than a 4 way intersecting when I'm in a car even if it's annoying to have to slow down and accelerate again when there is very little or no traffic, which is normal in the countryside. It also consumes more fuel, wears the car, adds to pollution. It's different when I'm riding my bicycle. Roundabouts put me closer to cars, especially if there are traffic dividers that force cars closer to the side of the road. Then cars are usually slower than a bicycle in a small or medium sized roundabout (think of race bicycles with drop bars,) which adds up to chances of being packed between two cars. My feeling is that what's good for cars is bad for bicycles. As a cyclist I can see what's around me much better than when I'm in my car. Intersections don't feel like a problem because of the extra visibility. When I'm riding I long for old times straight roads, with a line on the side and half a meter of asphalt on the other side to ride on. No roundabouts, no speed bumps especially the 3M style plastic ones, which I can jump but they are annoying. All those safety devices, including roundabouts, increase fatigue and danger. They are also the main reason for crashes in bicycle races but that's not an issue for normal people. Finally, as I both drive and ride I know how to behave not to put in danger the cyclist. When I drive I don't overtake bicycles before a roundabout because they'll be at least as fast as me. I don't overtake when there is a short traffic divider which narrows the road. A long one, oh well, I have to. Same thing when I approach an intersection where I have to yield or stop. Bicycles will be definitely faster there because they can look around better than me and decide what to do quickly. When I ride and I'm approaching a roundabout or entering a short narrowing of the road I look behind me and if it's safe I lean a little to the center of the road to prevent cars to overtake when they'll be forced to come close to me.
- axiolite 3y ago
  Your observations are quite apt. "Researchers in Belgium found that single lane roundabouts without a protected bike lane increased crashes by 93%, while Danish researchers said roundabouts that did have separated lanes saw an 84% reduction in crashes." CNBC: Roundabouts Are Safer. So Why Does The U.S. Have So Few Of Them? https://www.youtube.com/watch?v=atORPw-w83I https://www.youtube.com/watch?v=atORPw-w83I
- usrusr 3y ago
  Ah, those traffic dividers, clearly designed by people assuming that all roads should be limited access... "All those safety devices, including roundabouts, increase fatigue and danger." They literally distract from the traffic when you aren't in a little isolated house on wheels where people are prone to forget that traffic even exists. All those things designed to help getting a driver's eyes off WhatsApp require cyclists to get their eyes away from traffic. On the topic of roundabouts, one thing I rarely see discussed (never?) is that traffic lights conveniently compress the vehicle stream into packets of high and low intensity, greatly helping smaller intersections downstream. Roundabouts on the other hand flatten the vehicle frequency and of there's a difficult place to enter or cross the stream, even a modest amount of traffic can be too much. In the end everything that isn't a roundabout can only be navigated by relying on someone in the dominant stream showing off compassion with those waiting. This makes everything go even slower and you quickly end up with even dominant streams going less than walking speeds. I have a hypothesis that roundabout-dominated road graphs are particularly prone to effective throughput dropping once a certain threshold of throughput demand is reached. Traffic light dominated graphs are immune to this if drivers are just a little careful to not enter an intersection before they can assume that they will be able to leave before the lights change.