5 ms·

I'm having trouble understanding this article. If the count down timers show pedestrians the amount of time they have to cross the road (as they do here in Lond

by datr 12y ago

I'm having trouble understanding this article. If the count down timers show pedestrians the amount of time they have to cross the road (as they do here in London) why would the driver be watching this and think they only have a few seconds until the light goes red and they can't get through the intersection. Surely, the opposite is the case? I can see that you could potentially form a similar explanation around that scenario too but it doesn't seem as convincing.

ealexhudson 12y ago
I'm assuming this has something to do with being able to turn through a red light, which is illegal in London. But yeah. I had trouble understanding the issue at all, as you note London has them, I've never noticed any issue at all - if anything, it gets the peds out of the road more timely...
- joncrocks 12y ago
  Indeed, in England pedestrians never cross when a vehicle has a green light over the path they are going to cross. I.e. completely separate pedestrian phases. In the US, the walk lights go 'green' at the same time as traffic parallel to the crosswalk gets a green light, in a shared phase. So if the timer is getting close to zero, it means the vehicles are about to go to a red light, and the opposite direction is about to get the green light.
  - vidarh 12y ago
    I'm a bit unsure exactly what it is you are describing. Pretty much all the crossings I use regularly in London follows an at least very similar pattern to what I'm used to seeing in the US when visiting, with traffic parallel to the crossing getting green at the same time as the pedestrian crossing in question In fact, here's a discussion in the UK Parliament in 2004 where it was proposed to restrict the use of all-red phases in low traffic junctions, and where the person proposing the change saw it as necessary to describe why this was even an issue: http://www.publications.parliament.uk/pa/cm200304/cmstand/a/st040210/pm/40210s05.htm http://www.publications.parliament.uk/pa/cm200304/cmstand/a/... "Mr. Redwood: Until a few years ago, no one would have understood why new clause 5 would be necessary. All traffic lights that motorists or cyclists encountered on our highways had a simple form of operation which meant that there was always one free route across the junction showing green. In the normal four-way junction where two roads intersected, one road had priority for one phase and the other road had the alternate priority. There could be more complicated variations at larger junctions, but there was always a green phase for vehicles on one part of the junction" [The proposed clause 5: 'No authority shall be entitled to install or operate traffic signals with all red phases at road junctions where there is no hazard other than traffic.'] You may be right that no vehicles will have green light to cross the pedestrian crossing while pedestrians have a green light, though I'm not 100% sure that's true either - I seem to remember crossings in London at least where turning traffic will have green at the same time as pedestrians, but I don't drive so maybe that's just me as an impatient pedestrian misremembering, as I'll regularly cross on red.
    - ealexhudson 12y ago
      I've never seen or heard of that in the UK: if the green man shows, no vehicle can cross the path. It's quite common for traffic to be moving while some part of the crossing is green, but they wouldn't be allowed to use that lane. Indeed, pedestrians will regularly cross at red man - that's allowed, and people know they need to look out in all directions. All-red phases are a slightly different issue, and indeed, not all crossings have them
    - ascorbic 12y ago
      I think the confusion here is that in the UK there is a separate phase for drivers turning left into the junction, whereas in the U.S. drivers can turn right across the path of crossing pedestrians. Obviously the UK system is a lot safer.
    - joncrocks 12y ago
      As ealexhudson says here: https://news.ycombinator.com/item?id=7975422 https://news.ycombinator.com/item?id=7975422 , the difference is that in the UK, when you have a 'green man', there is a guarantee that traffic are not permitted to use any piece of road you are crossing. I was describing the crossroads situation where all vehicles are allowed to travel in any direction when they have a green light (no filter light/lanes), as this is the most commonly occurring situation in towns in the US I think. Not including states where there is a propensity for 'no left turn' intersections. In the US, this would mean two phases, with each one being a shared pedestrian and vehicle phase, pedestrians crossing in parallel to traffic. In the UK this would be three phases, two traffic and one dedicated pedestrian phase. I personally prefer the UK system, as in the US as a pedestrian you are at the whim of drivers paying attention to pedestrian traffic, and even if they don't hit you they may well start turning the corner to pressure you to hurry up.
walexander 12y ago
A crosswalk that is parallel to you (i.e., pedestrians traveling in the same direction across the intersection as the drivers) will have a "walk" signal that is synched with the traffic light. In this case, a green light would be analogous to "walk" and a yellow light would be analogous to "3..2..1..". It is likely that once the cross walk reaches zero, a yellow light will appear on the traffic signal. Anyone reading the walk signal in front of them will have an early warning about the traffic light and may try to speed up to get through. If you're a block away from the light and you see a "4", what do you do?
- jonemo 12y ago
  The essential piece of information missing from the article, because it's common in the US, is that pedestrians usually get green at the same time as traffic in parallel with them. In Europe it's a more common pattern that all pedestrians walk at an interval when all traffic is stopped and this cheat would indeed not work there.
  - morsch 12y ago
    Not once have I seen this anywhere in Europe. I'm sure you're talking from experience and it's a thing, but it seems to vary from place to place. It sounds a bit inefficient.
    - judk 12y ago
      Indeed, it is less efficient when cars have to stop for pedestrians and not drive through them.
    - vidarh 12y ago
      I don't think it's that common - I've only seen it a couple of places, but it happens. Most places in Europe I've been, there's car traffic going in parallel with the pedestrians. The most "famous" example in Europe of all traffic being stopped at once, I suspect is Oxford Circus in London, where they changed to start doing this a few years ago. The reason to do it there, though, was to allow pedestrians to walk in any direction (diagonally as well) across one of the busiest crossings in the country. This BBC article refers to it as a "Japanese-styled system": http://news.bbc.co.uk/1/hi/england/london/7997569.stm http://news.bbc.co.uk/1/hi/england/london/7997569.stm
zaphoyd 12y ago
Normally after the pedestrian countdown is finished the light turns yellow, then red for traffic moving in the same direction. Traffic in the perpendicular direction then gets a green light making it unsafe for pedestrians to cross. The issue is that vehicles moving in the same direction as the pedestrians can also see the pedestrian countdown and can use that information to determine approximately how much longer their own vehicle light will remain green. The article suggests that that different drivers interpret the countdown information differently than the green/yellow/red lights and more specifically, and unlike the colored lights, different drivers interpret the countdown timer differently (some see 3 seconds and speed up, others see 3 seconds and slow down).
mturmon 12y ago
The article is correct, and it is a real phenomenon in LA where I live. To address your question, which I (humorously) don't really get -- the pedestrians who have the countdown and the cars are moving parallel to each other. The drivers and the peds are both looking in the same direction at the countdown timer.
threedaymonk 12y ago
Pedestrian crossings in the UK are rather unusual compared to most other countries in the world, in my experience. In most places, crossings work on a parallel/perpendicular system: parallel roads and pedestrian crossings are red or green[1] at the same time. This means that cars turning across a pedestrian crossing must give way (yield) to pedestrians. The UK system, by contrast, isolates the pedestrian phase from traffic phases: when the green man (the WALK indicator) is displayed, no vehicles will approach the pedestrian crossing from any direction. The time between pedestrian crossing opportunities is longer, but there is no contention for the crossing from cars turning into the road. The article describes the parallel/perpendicular system. In this scenario, a driver will see a parallel WALK light and a (vehicular) green light at the same time. As the pedestrian crossing typically goes red earlier (because people take longer to cross the road than cars take to cross the intersection), a car driver who watches the pedestrian crossing light or countdown timer gains advanced knowledge of the parallel traffic signal. 1. Or white in some places in the US!
- deleted 12y ago
  [deleted]
- Rapzid 12y ago
  New Zealand has a mix. All stop, all direction crossings are usually reserved for downtown high pedestrian flow intersections. There is also a distinction between green and green arrow turns. Green arrow indicates safe turns and green means yield to traffic/pedestrians.

by datr 12y ago

ealexhudson 12y ago

I'm assuming this has something to do with being able to turn through a red light, which is illegal in London. But yeah. I had trouble understanding the issue at all, as you note London has them, I've never noticed any issue at all - if anything, it gets the peds out of the road more timely...

joncrocks 12y ago
Indeed, in England pedestrians never cross when a vehicle has a green light over the path they are going to cross. I.e. completely separate pedestrian phases. In the US, the walk lights go 'green' at the same time as traffic parallel to the crosswalk gets a green light, in a shared phase. So if the timer is getting close to zero, it means the vehicles are about to go to a red light, and the opposite direction is about to get the green light.
- vidarh 12y ago
  I'm a bit unsure exactly what it is you are describing. Pretty much all the crossings I use regularly in London follows an at least very similar pattern to what I'm used to seeing in the US when visiting, with traffic parallel to the crossing getting green at the same time as the pedestrian crossing in question In fact, here's a discussion in the UK Parliament in 2004 where it was proposed to restrict the use of all-red phases in low traffic junctions, and where the person proposing the change saw it as necessary to describe why this was even an issue: http://www.publications.parliament.uk/pa/cm200304/cmstand/a/st040210/pm/40210s05.htm http://www.publications.parliament.uk/pa/cm200304/cmstand/a/... "Mr. Redwood: Until a few years ago, no one would have understood why new clause 5 would be necessary. All traffic lights that motorists or cyclists encountered on our highways had a simple form of operation which meant that there was always one free route across the junction showing green. In the normal four-way junction where two roads intersected, one road had priority for one phase and the other road had the alternate priority. There could be more complicated variations at larger junctions, but there was always a green phase for vehicles on one part of the junction" [The proposed clause 5: 'No authority shall be entitled to install or operate traffic signals with all red phases at road junctions where there is no hazard other than traffic.'] You may be right that no vehicles will have green light to cross the pedestrian crossing while pedestrians have a green light, though I'm not 100% sure that's true either - I seem to remember crossings in London at least where turning traffic will have green at the same time as pedestrians, but I don't drive so maybe that's just me as an impatient pedestrian misremembering, as I'll regularly cross on red.
  - ealexhudson 12y ago
    I've never seen or heard of that in the UK: if the green man shows, no vehicle can cross the path. It's quite common for traffic to be moving while some part of the crossing is green, but they wouldn't be allowed to use that lane. Indeed, pedestrians will regularly cross at red man - that's allowed, and people know they need to look out in all directions. All-red phases are a slightly different issue, and indeed, not all crossings have them
  - ascorbic 12y ago
    I think the confusion here is that in the UK there is a separate phase for drivers turning left into the junction, whereas in the U.S. drivers can turn right across the path of crossing pedestrians. Obviously the UK system is a lot safer.
  - joncrocks 12y ago
    As ealexhudson says here: https://news.ycombinator.com/item?id=7975422 https://news.ycombinator.com/item?id=7975422 , the difference is that in the UK, when you have a 'green man', there is a guarantee that traffic are not permitted to use any piece of road you are crossing. I was describing the crossroads situation where all vehicles are allowed to travel in any direction when they have a green light (no filter light/lanes), as this is the most commonly occurring situation in towns in the US I think. Not including states where there is a propensity for 'no left turn' intersections. In the US, this would mean two phases, with each one being a shared pedestrian and vehicle phase, pedestrians crossing in parallel to traffic. In the UK this would be three phases, two traffic and one dedicated pedestrian phase. I personally prefer the UK system, as in the US as a pedestrian you are at the whim of drivers paying attention to pedestrian traffic, and even if they don't hit you they may well start turning the corner to pressure you to hurry up.

walexander 12y ago

A crosswalk that is parallel to you (i.e., pedestrians traveling in the same direction across the intersection as the drivers) will have a "walk" signal that is synched with the traffic light. In this case, a green light would be analogous to "walk" and a yellow light would be analogous to "3..2..1..". It is likely that once the cross walk reaches zero, a yellow light will appear on the traffic signal. Anyone reading the walk signal in front of them will have an early warning about the traffic light and may try to speed up to get through. If you're a block away from the light and you see a "4", what do you do?

jonemo 12y ago
The essential piece of information missing from the article, because it's common in the US, is that pedestrians usually get green at the same time as traffic in parallel with them. In Europe it's a more common pattern that all pedestrians walk at an interval when all traffic is stopped and this cheat would indeed not work there.
- morsch 12y ago
  Not once have I seen this anywhere in Europe. I'm sure you're talking from experience and it's a thing, but it seems to vary from place to place. It sounds a bit inefficient.
  - judk 12y ago
    Indeed, it is less efficient when cars have to stop for pedestrians and not drive through them.
  - vidarh 12y ago
    I don't think it's that common - I've only seen it a couple of places, but it happens. Most places in Europe I've been, there's car traffic going in parallel with the pedestrians. The most "famous" example in Europe of all traffic being stopped at once, I suspect is Oxford Circus in London, where they changed to start doing this a few years ago. The reason to do it there, though, was to allow pedestrians to walk in any direction (diagonally as well) across one of the busiest crossings in the country. This BBC article refers to it as a "Japanese-styled system": http://news.bbc.co.uk/1/hi/england/london/7997569.stm http://news.bbc.co.uk/1/hi/england/london/7997569.stm

zaphoyd 12y ago

Normally after the pedestrian countdown is finished the light turns yellow, then red for traffic moving in the same direction. Traffic in the perpendicular direction then gets a green light making it unsafe for pedestrians to cross. The issue is that vehicles moving in the same direction as the pedestrians can also see the pedestrian countdown and can use that information to determine approximately how much longer their own vehicle light will remain green. The article suggests that that different drivers interpret the countdown information differently than the green/yellow/red lights and more specifically, and unlike the colored lights, different drivers interpret the countdown timer differently (some see 3 seconds and speed up, others see 3 seconds and slow down).

mturmon 12y ago

The article is correct, and it is a real phenomenon in LA where I live. To address your question, which I (humorously) don't really get -- the pedestrians who have the countdown and the cars are moving parallel to each other. The drivers and the peds are both looking in the same direction at the countdown timer.

threedaymonk 12y ago

Pedestrian crossings in the UK are rather unusual compared to most other countries in the world, in my experience. In most places, crossings work on a parallel/perpendicular system: parallel roads and pedestrian crossings are red or green[1] at the same time. This means that cars turning across a pedestrian crossing must give way (yield) to pedestrians. The UK system, by contrast, isolates the pedestrian phase from traffic phases: when the green man (the WALK indicator) is displayed, no vehicles will approach the pedestrian crossing from any direction. The time between pedestrian crossing opportunities is longer, but there is no contention for the crossing from cars turning into the road. The article describes the parallel/perpendicular system. In this scenario, a driver will see a parallel WALK light and a (vehicular) green light at the same time. As the pedestrian crossing typically goes red earlier (because people take longer to cross the road than cars take to cross the intersection), a car driver who watches the pedestrian crossing light or countdown timer gains advanced knowledge of the parallel traffic signal. 1. Or white in some places in the US!

deleted 12y ago
[deleted]
Rapzid 12y ago
New Zealand has a mix. All stop, all direction crossings are usually reserved for downtown high pedestrian flow intersections. There is also a distinction between green and green arrow turns. Green arrow indicates safe turns and green means yield to traffic/pedestrians.