3 ms·

And then you get roundabouts with traffic lights like in the UK. I'm sure there are good reasons for that, but, as someone that hardly drives in the UK, I was v

And then you get roundabouts with traffic lights like in the UK. I'm sure there are good reasons for that, but, as someone that hardly drives in the UK, I was very very surprised the first time I encountered them.

anyonecancode 4y ago
Oh, that's nothing. Here in New Jersey, we have what my wife refers to as a "traffic theta". Here's an example: https://www.google.com/maps/@40.7957351,-74.3405952,17z https://www.google.com/maps/@40.7957351,-74.3405952,17z It's a circle, with traffic light, but also still an intersection. Fun!
d1sxeyes 4y ago
You generally get these when the roundabout has one or more clear 'through traffic' routes, to the point that you're always 'giving way to the right' and not able to enter the roundabout. If you imagine traffic on a motorway going North/South and an A-road running East-West, at busy times, the traffic going from East to West and West to East will be significant enough that traffic coming off the motorway is not able to find enough space to enter the roundabout (or, not enough to meet the demand). Without traffic lights, traffic will soon back up down the slip road onto the motorway, or worse, will try to force its way onto the roundabout instead of giving way to the right. Traffic lights make this much safer.
- alistairSH 4y ago
  Or some arrangement of flyovers, ramps, etc (double diamond interchange being the current flavor of the month here in the US mid-Atlantic). Obviously, only makes sense for actual motorways, not going to get one in mid-town London, hopefully.
  - avianlyric 4y ago
    Land is expensive enough, and built up enough, in the UK that flyovers are pretty much not an option near any major road anymore. In general the UK has very few flyovers. I sometimes suspect the SF Bay Area has more flyovers than the entire of the UK.
cameronh90 4y ago
In addition, in areas with very high traffic, like London, area-coordinated adaptive traffic light systems (see SCOOT/SCATS) are used to keep traffic flowing smoothly, stop congestion from blocking junctions, prioritise emergency services and more. These systems are very good at what they do. Traffic lights are also used to give priority to pedestrians and cyclists on junctions where it would be unsafe to rely on zebra crossings or pedestrian priority - think sharp and low visibility corners. As far as roundabouts go, the UK has been replacing big multi-lane roundabouts in areas with lots of pedestrians and cyclists with two-way-traffic horse shoes (e.g. Old Street and E&C, plus others outside of London). This allows the centre of the roundabout to be used as public space, and has been found to be safer for vulnerable road users. I'm all for light-free junctions where possible, and light-free roundabouts work REALLY well in low/medium traffic. But you can't just abolish traffic lights - unless we also abolish cars at the same time.
- wizofaus 4y ago
  Do you have a link to one of these "two-way horse shoes" on Google maps or similar? I'm curious how they solve the problem of needing to taking the 3rd exit on a multi-lane roundabout while on a bicycle.
  - avianlyric 4y ago
    Pretty simple. The section of road between 3rd exit and the 4th (which is also where you enter) is completely removed. So taking the 3rd exit on a bike either means following the road all the way around, or just going directly from the entrance to the 3rd exit, as cycle lane is usually preserved where the road used to be.
    - wizofaus 4y ago
      I looked at that E&C "horseshoe" - it still looks hairy if you're riding north on the A3 and want to turn right into the A201, given the number of crossings of busy roads with no traffic signals. But better than some of the busy 3-lane roundabouts I've had to navigate here with no provision for bicycles (or pedestrians really) at all.

anyonecancode 4y ago

Oh, that's nothing. Here in New Jersey, we have what my wife refers to as a "traffic theta". Here's an example: https://www.google.com/maps/@40.7957351,-74.3405952,17z https://www.google.com/maps/@40.7957351,-74.3405952,17z It's a circle, with traffic light, but also still an intersection. Fun!

d1sxeyes 4y ago

You generally get these when the roundabout has one or more clear 'through traffic' routes, to the point that you're always 'giving way to the right' and not able to enter the roundabout. If you imagine traffic on a motorway going North/South and an A-road running East-West, at busy times, the traffic going from East to West and West to East will be significant enough that traffic coming off the motorway is not able to find enough space to enter the roundabout (or, not enough to meet the demand). Without traffic lights, traffic will soon back up down the slip road onto the motorway, or worse, will try to force its way onto the roundabout instead of giving way to the right. Traffic lights make this much safer.

alistairSH 4y ago
Or some arrangement of flyovers, ramps, etc (double diamond interchange being the current flavor of the month here in the US mid-Atlantic). Obviously, only makes sense for actual motorways, not going to get one in mid-town London, hopefully.
- avianlyric 4y ago
  Land is expensive enough, and built up enough, in the UK that flyovers are pretty much not an option near any major road anymore. In general the UK has very few flyovers. I sometimes suspect the SF Bay Area has more flyovers than the entire of the UK.

cameronh90 4y ago

In addition, in areas with very high traffic, like London, area-coordinated adaptive traffic light systems (see SCOOT/SCATS) are used to keep traffic flowing smoothly, stop congestion from blocking junctions, prioritise emergency services and more. These systems are very good at what they do. Traffic lights are also used to give priority to pedestrians and cyclists on junctions where it would be unsafe to rely on zebra crossings or pedestrian priority - think sharp and low visibility corners. As far as roundabouts go, the UK has been replacing big multi-lane roundabouts in areas with lots of pedestrians and cyclists with two-way-traffic horse shoes (e.g. Old Street and E&C, plus others outside of London). This allows the centre of the roundabout to be used as public space, and has been found to be safer for vulnerable road users. I'm all for light-free junctions where possible, and light-free roundabouts work REALLY well in low/medium traffic. But you can't just abolish traffic lights - unless we also abolish cars at the same time.

wizofaus 4y ago
Do you have a link to one of these "two-way horse shoes" on Google maps or similar? I'm curious how they solve the problem of needing to taking the 3rd exit on a multi-lane roundabout while on a bicycle.
- avianlyric 4y ago
  Pretty simple. The section of road between 3rd exit and the 4th (which is also where you enter) is completely removed. So taking the 3rd exit on a bike either means following the road all the way around, or just going directly from the entrance to the 3rd exit, as cycle lane is usually preserved where the road used to be.
  - wizofaus 4y ago
    I looked at that E&C "horseshoe" - it still looks hairy if you're riding north on the A3 and want to turn right into the A201, given the number of crossings of busy roads with no traffic signals. But better than some of the busy 3-lane roundabouts I've had to navigate here with no provision for bicycles (or pedestrians really) at all.