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The only case where bike paths do generate congestion is when you add them to roundabouts. This is done atrociously in Denmark, effectively negating all benefit

by slau 2y ago

The only case where bike paths do generate congestion is when you add them to roundabouts. This is done atrociously in Denmark, effectively negating all benefits of roundabouts—-most likely the reason there are barely any roundabouts in agglomerations. There is one example in particular (the one between Ørestads Boulevard and Grønjordsvej for any locals reading this). Cycles have right of way, which prevents cars from exiting the roundabout smoothly. At rush hour, this very quickly generates massive queues (in comparison with the amount of traffic), and can sometimes get completely gridlocked.

DemocracyFTW2 2y ago
Granting anyone—busses, streetcars, pedestrians, bicycles—priority over CARS is verboten right, because that 'blocks traffic'.
- DiggyJohnson 2y ago
  You are being snarky. GPs point is literally that the main benefits of a traffic circle - safety and uninterrupted flow - are negatives by how the roundabout is shared with bikes… thus it could have been a different style of intersection if the plan was to share with bikes.
  - DemocracyFTW2 2y ago
    I'm being snarky because I believe that giving traffic other than cars priority at crossings and in roundabouts is the way to go. I live on a busy city street; traffic has become worse and worse and it has become ever more difficult to cross the street. This has in recent years been alleviated by two means: some unmarked crossings with a traffic island between the lanes, meaning now you have a relatively safe spot that allows you to cross while paying attention to one direction at a time. The other is a zebra crossing where cars have to stop for crossing pedestrians. The latter works very well and I much prefer it to the traffic islands and to the traffic lights that are further down the street. And yes the cars (and cyclists) have to stop for pedestrians, but that is intentional: yield to the weaker one. Besides traffic has become so congested overall that it's not like there's any measurable time lost for the car driver, and who ever accounted for the endless waiting times that pedestrians have to endure at traffic light crossings when walking the city? In any event the daily traffic jam is definitely not caused by bicycles or pedestrians, with or without priority given to them—it is 100% caused by cars.
    - Spivak 2y ago
      Hard disagree, even as a pedestrian it doesn't make sense to have right-of-way over cars. They de facto have it anyway since I'm not suicidal. It's annoying as hell when cars stop for me, like no just go you'll be past me by the time I take one step you're wasting your own time by stopping. And when there's a continuous stream of cars and no window to cross batching everyone at signaled intersections is more efficient and safer for everyone. Everyone stops at reds and you can physically see them stopped. A zebra crossing on a busy street just takes one person not seeing you.
      - DemocracyFTW2 2y ago
        When you go to Poland they have zebra crossings all over the place, they favor them over pedestrian traffic lights. The entire country disagrees with you. But I agree that you have to exert some care and judgement when using a zebra crossing. You must look and be prepared for the (in my experience, in Germany) occasional driver who speeds instead of stopping. I cannot entirely share your warm affections for traffic lights, for that I've had too many perilous events where entitled reckless drivers think they can drive like assholes with impunity. At least where I live pedestrians at intersections share their green phase with the cars in the same direction and the cars turning right and left, meaning you potentially have a green light but a steady stream of cars coming from left behind you (they mostly are slow having stopped anyway, but the do crawl up from behind) and left front of you (those in some intersection tend to come with a certain speed they picked up when crossing). At least in areas where people live pedestrians must always have, in principle, right of way. As my driving teacher told me, you as a driver have to look both ways and prepared; yes, a pedestrian is not allowed to cross here, but then you as a driver are not allow to run over the guy either.
- slau 2y ago
  Interesting point of view, but very far from what I said. I think blocking any traffic, be it pedestrian, cyclist or cars is bad. I would also wager that forcing cycles to cross over car roads is terrible from a safety perspective, exactly because both are going at speed, and both are in each other’s “dead angle”. In this article[1], they claim 70% of accidents in roundabouts are due to cars not seeing cycles. I do believe that drivers in Copenhagen are by-and-large more acquainted with cyclists popping up, but still. The same article documents an experiment in France where cyclists are invited to occupy the middle lane of the roundabout, and just behave as a car would. It makes them more visible (both by cars in the roundabout and those trying to enter), and removes the number of “exceptions”. It would most likely slow down car traffic, but that’s fine. The important thing is to not come to an absolute stop. There’s also a study by CEREMA on how to enable cyclists to utilise and be safer in roundabouts: https://www.cerema.fr/fr/system/files?file=documents/2017/12/CEREMA_Etude_Positionnement-cycliste-giratoire_cle1a154e.pdf https://www.cerema.fr/fr/system/files?file=documents/2017/12... [1]: https://13commeune.fr/actualite/ronds-points-quand-les-velos-circulent-au-milieu-cest-mieux/ https://13commeune.fr/actualite/ronds-points-quand-les-velos...
ano-ther 2y ago
> Cycles have right of way, which prevents cars from exiting the roundabout smoothly. At rush hour, this very quickly generates massive queues Isn’t that more a result of the roundabout being overloaded? That particular one can be quite full even in non-bike weather.
- slau 2y ago
  I’m not sure it is. 90% of the time it congests on a specific exit—the one going south, and this is entirely due to all the cycles coming from indreby that need to go to the residential area east of that roundabout. Having grown up in France, I know the insane capacity that roundabouts can have, and I don’t think CPH traffic is anywhere near that. It’s just poor design in some places.
  - ano-ther 2y ago
    I see what you mean. The continuous stream of bikes in the (outer) bike lane trapping the cars that want to exit. How do they do that in France? My only solution would be to merge bikes and cars ahead of the roundabout which requires some caution especially from the car drivers.
    - slau 2y ago
      I've been wondering the same. To be fair, there were barely any bike lanes in the area I grew up, but roundabouts were legion. I did explain one technique, where you basically have bikes enter the roundabout and "block" the inner lane as if they were a car, see here: https://news.ycombinator.com/item?id=41924222 https://news.ycombinator.com/item?id=41924222. I don't know if it's safer or not, but it is one technique that is legal in France since 2015, and an official recommendation to city planners. Having a cursory look at Google Maps, I see four techniques: move the bike path completely away from the car road, force cyclists to dismount and behave like pedestrians (and use the zebras around the roundabout), allow cyclists to behave like cars and occupy the center lane(s), and the "bike path around the roundabout" technique. I think both bike-path-around-the-roundabout and forcing cyclists to become pedestrians are equally terrible solutions. Moving the cycle paths away from roads is situational and doesn't really address the crux of the issue. I'll have to try and find more data/experience about the roundabouts that let bikes behave like cars and see how it is. Depending on the roundabout, that must be a harrowing experience. I think building a pedestrian/cyclist bridge or tunnel could be a solid answer. Or maybe the other way around, because it's still mechanically easier for cars to go up an incline than for cyclists/pedestrians, at the cost of much, much more maintenance.

by slau 2y ago

DemocracyFTW2 2y ago

Granting anyone—busses, streetcars, pedestrians, bicycles—priority over CARS is verboten right, because that 'blocks traffic'.

DiggyJohnson 2y ago
You are being snarky. GPs point is literally that the main benefits of a traffic circle - safety and uninterrupted flow - are negatives by how the roundabout is shared with bikes… thus it could have been a different style of intersection if the plan was to share with bikes.
- DemocracyFTW2 2y ago
  I'm being snarky because I believe that giving traffic other than cars priority at crossings and in roundabouts is the way to go. I live on a busy city street; traffic has become worse and worse and it has become ever more difficult to cross the street. This has in recent years been alleviated by two means: some unmarked crossings with a traffic island between the lanes, meaning now you have a relatively safe spot that allows you to cross while paying attention to one direction at a time. The other is a zebra crossing where cars have to stop for crossing pedestrians. The latter works very well and I much prefer it to the traffic islands and to the traffic lights that are further down the street. And yes the cars (and cyclists) have to stop for pedestrians, but that is intentional: yield to the weaker one. Besides traffic has become so congested overall that it's not like there's any measurable time lost for the car driver, and who ever accounted for the endless waiting times that pedestrians have to endure at traffic light crossings when walking the city? In any event the daily traffic jam is definitely not caused by bicycles or pedestrians, with or without priority given to them—it is 100% caused by cars.
  - Spivak 2y ago
    Hard disagree, even as a pedestrian it doesn't make sense to have right-of-way over cars. They de facto have it anyway since I'm not suicidal. It's annoying as hell when cars stop for me, like no just go you'll be past me by the time I take one step you're wasting your own time by stopping. And when there's a continuous stream of cars and no window to cross batching everyone at signaled intersections is more efficient and safer for everyone. Everyone stops at reds and you can physically see them stopped. A zebra crossing on a busy street just takes one person not seeing you.
    - DemocracyFTW2 2y ago
      When you go to Poland they have zebra crossings all over the place, they favor them over pedestrian traffic lights. The entire country disagrees with you. But I agree that you have to exert some care and judgement when using a zebra crossing. You must look and be prepared for the (in my experience, in Germany) occasional driver who speeds instead of stopping. I cannot entirely share your warm affections for traffic lights, for that I've had too many perilous events where entitled reckless drivers think they can drive like assholes with impunity. At least where I live pedestrians at intersections share their green phase with the cars in the same direction and the cars turning right and left, meaning you potentially have a green light but a steady stream of cars coming from left behind you (they mostly are slow having stopped anyway, but the do crawl up from behind) and left front of you (those in some intersection tend to come with a certain speed they picked up when crossing). At least in areas where people live pedestrians must always have, in principle, right of way. As my driving teacher told me, you as a driver have to look both ways and prepared; yes, a pedestrian is not allowed to cross here, but then you as a driver are not allow to run over the guy either.
slau 2y ago
Interesting point of view, but very far from what I said. I think blocking any traffic, be it pedestrian, cyclist or cars is bad. I would also wager that forcing cycles to cross over car roads is terrible from a safety perspective, exactly because both are going at speed, and both are in each other’s “dead angle”. In this article[1], they claim 70% of accidents in roundabouts are due to cars not seeing cycles. I do believe that drivers in Copenhagen are by-and-large more acquainted with cyclists popping up, but still. The same article documents an experiment in France where cyclists are invited to occupy the middle lane of the roundabout, and just behave as a car would. It makes them more visible (both by cars in the roundabout and those trying to enter), and removes the number of “exceptions”. It would most likely slow down car traffic, but that’s fine. The important thing is to not come to an absolute stop. There’s also a study by CEREMA on how to enable cyclists to utilise and be safer in roundabouts: https://www.cerema.fr/fr/system/files?file=documents/2017/12/CEREMA_Etude_Positionnement-cycliste-giratoire_cle1a154e.pdf https://www.cerema.fr/fr/system/files?file=documents/2017/12... [1]: https://13commeune.fr/actualite/ronds-points-quand-les-velos-circulent-au-milieu-cest-mieux/ https://13commeune.fr/actualite/ronds-points-quand-les-velos...

ano-ther 2y ago

> Cycles have right of way, which prevents cars from exiting the roundabout smoothly. At rush hour, this very quickly generates massive queues Isn’t that more a result of the roundabout being overloaded? That particular one can be quite full even in non-bike weather.

slau 2y ago
I’m not sure it is. 90% of the time it congests on a specific exit—the one going south, and this is entirely due to all the cycles coming from indreby that need to go to the residential area east of that roundabout. Having grown up in France, I know the insane capacity that roundabouts can have, and I don’t think CPH traffic is anywhere near that. It’s just poor design in some places.
- ano-ther 2y ago
  I see what you mean. The continuous stream of bikes in the (outer) bike lane trapping the cars that want to exit. How do they do that in France? My only solution would be to merge bikes and cars ahead of the roundabout which requires some caution especially from the car drivers.
  - slau 2y ago
    I've been wondering the same. To be fair, there were barely any bike lanes in the area I grew up, but roundabouts were legion. I did explain one technique, where you basically have bikes enter the roundabout and "block" the inner lane as if they were a car, see here: https://news.ycombinator.com/item?id=41924222 https://news.ycombinator.com/item?id=41924222. I don't know if it's safer or not, but it is one technique that is legal in France since 2015, and an official recommendation to city planners. Having a cursory look at Google Maps, I see four techniques: move the bike path completely away from the car road, force cyclists to dismount and behave like pedestrians (and use the zebras around the roundabout), allow cyclists to behave like cars and occupy the center lane(s), and the "bike path around the roundabout" technique. I think both bike-path-around-the-roundabout and forcing cyclists to become pedestrians are equally terrible solutions. Moving the cycle paths away from roads is situational and doesn't really address the crux of the issue. I'll have to try and find more data/experience about the roundabouts that let bikes behave like cars and see how it is. Depending on the roundabout, that must be a harrowing experience. I think building a pedestrian/cyclist bridge or tunnel could be a solid answer. Or maybe the other way around, because it's still mechanically easier for cars to go up an incline than for cyclists/pedestrians, at the cost of much, much more maintenance.