4 ms·

What if they moved the bike/pedestrian crossings to further along the lanes away from the roundabout? This would give more room for the cars to exit the roundab

What if they moved the bike/pedestrian crossings to further along the lanes away from the roundabout? This would give more room for the cars to exit the roundabout without encountering immediate cross traffic, and more "collection space" on the exit itself so if a driver does have to stop to let a pedestrian/cyclist through they don't impede the roundabout traffic.

Kim_Bruning 5y ago
Posted video link of this type of roundabout in action just above ( https://news.ycombinator.com/item?id=27415631 https://news.ycombinator.com/item?id=27415631 ) There's just sufficient space for 1 car to tuck in each time. Note that the priority here is not necessarily to maximize car throughput at all costs; but to ensure safety for all modes of traffic; and to do so inside a given amount of space and cost. Given a different set of parameters, a different intersection type might be chosen. (+) That said, note in the video that there's a significant number of people using the bicycle lane and pedestrian path; I think they're carrying more people than the car lanes here. I'm not a traffic expert, but forcing the denser traffic to take a longer route in favor of the less dense traffic does not seem like the right choice here. ;-)
- raffraffraff 5y ago
  It seems to work during that 5 minute segment, but at 1.45 it looks like this system could get gridlocked. If vehicles are blocked from exiting a roundabout for long enough, there's a risk that the whole thing will fill up. When this happens, it can only get unblocked quickly if the vehicles blocking the exits wish to leave via those exits. Edit: nope, the system can continue to move, but when more exits are blocked, the system throughput drops sharply to zero. I'd love to see this roundabout during rush hour. For cyclists safety, this system works because the cycle lane is so far outside the vehicle lane, and it is right before pedestrian crossing. Most of the roundabouts with bicycle lanes that I have encountered, they just used a different coloured tarmac at the edge to show cyclists where they should risk their lives. They're not at 90 degrees to the cars, they're literally side-by-side. In that situation, cyclists are in greater danger of getting side-swiped by a car exiting the roundabout.

Kim_Bruning 5y ago

Posted video link of this type of roundabout in action just above ( https://news.ycombinator.com/item?id=27415631 https://news.ycombinator.com/item?id=27415631 ) There's just sufficient space for 1 car to tuck in each time. Note that the priority here is not necessarily to maximize car throughput at all costs; but to ensure safety for all modes of traffic; and to do so inside a given amount of space and cost. Given a different set of parameters, a different intersection type might be chosen. (+) That said, note in the video that there's a significant number of people using the bicycle lane and pedestrian path; I think they're carrying more people than the car lanes here. I'm not a traffic expert, but forcing the denser traffic to take a longer route in favor of the less dense traffic does not seem like the right choice here. ;-)

raffraffraff 5y ago
It seems to work during that 5 minute segment, but at 1.45 it looks like this system could get gridlocked. If vehicles are blocked from exiting a roundabout for long enough, there's a risk that the whole thing will fill up. When this happens, it can only get unblocked quickly if the vehicles blocking the exits wish to leave via those exits. Edit: nope, the system can continue to move, but when more exits are blocked, the system throughput drops sharply to zero. I'd love to see this roundabout during rush hour. For cyclists safety, this system works because the cycle lane is so far outside the vehicle lane, and it is right before pedestrian crossing. Most of the roundabouts with bicycle lanes that I have encountered, they just used a different coloured tarmac at the edge to show cyclists where they should risk their lives. They're not at 90 degrees to the cars, they're literally side-by-side. In that situation, cyclists are in greater danger of getting side-swiped by a car exiting the roundabout.