5 ms·

The idea is cool, but if you are in a US context, outside of a core city, please understand that your being delayed is actually part of the feature set of a sto

The idea is cool, but if you are in a US context, outside of a core city, please understand that your being delayed is actually part of the feature set of a stop light. Delaying you and other drivers allows gaps in traffic that let people enter relatively high-speed, unlimited-access roads that cover the US. It takes a lot of open space to safely enter a fast road. The alternative would be to narrow roads and lower speed limits as traffic intensifies, mitigating the need for stop lights. Unfortunately, design speed is the priority: we do whatever it takes to make sure that cars, when they are not stopped by lights or other traffic, can safely(ish) travel at the design speed.

cvoss 2y ago
This is very true. I routinely depend on stop lights to govern intersections other than the intersection the light is posted at. And when I'm sitting at a red light with a bunch of other people, complaining to myself about how inefficient it seems because there is currently no cross traffic, I have to remind myself we are helping people downstream from the intersection to enter the road.
- cowsaymoo 2y ago
  cognitive behavioral therapy enjoyer:
smilekzs 2y ago
The goal you described matches more of an on-ramp meter instead of surface street lights? Unless of course we're talking about an intersection leading to the on-ramp, but now we're into back-off effects as well, which arguably could use more smartness in their schedule.
- QuarterReptile 2y ago
  It's sort of the reverse, in a sense. If drivers adhered strictly to yield signs, those getting onto the highway would wait until there was a space in traffic. There would be times when you could not get on to the highway at all, when traffic was heavy but not so heavy that it slowed. To solve this (again, with strictly following RoW), you would have to either slow speeds on the highway or put stop lights on the highway to let mergers enter the roadway. This doesn't happen because everyone understands that those merging onto the highway are moving fast and running out of space, and prudence dictates that you slow down to make space, rather than finding out if you're driving next to someone who will crash into you. At the far end of the spectrum from that situation, you have people waiting forever to cross, in a marked crossing where they have right of way, because they're stopped (the status quo supports them not going) and they stand to die if the driver doesn't yield properly. Fast unlimited-access roads are somewhere in the middle: the mergers don't have the initiative, but the suffering is more evenly distributed in the case of a crash, so the passing drivers are perhaps more prepared to slam on brakes. The on-ramp meters provide the service of prioritizing drivers from distant suburbs or out of town at the expense of those who dwell in nearer suburbs. To put a different spin on it, they slightly disincentivize short trips on highways.
  - seadan83 2y ago
    I have trouble agreeing. > There would be times when you could not get on to the highway at all, when traffic was heavy but not so heavy that it slowed. The flowing traffic makes space for the merging traffic, which also takes up any existing gaps. The merging traffic ideally zipper merges at traffic speed. Traffic speed is correlated to gaps between cars. If merging gets tight, gap size is small, traffic is therefore going slower. If merging is impossible, then gap size is tiny, traffic speed is approaching zero, and both the onramp and highway are a traffic jam. It is the accumulation of new traffic that slows traffic speed. I think you are implying traffic speed remains a fixed constant and merging traffic just waits. Instead there is an interplay. Which comes to onramp lights. That is just a rate limiter to avoid the highway from going into an extreme bottleneck. The highway capacity is the bottleneck, so adding more traffic to it freely makes it exponentially worse. It is not at all about incentives but preservation of traffic flow. The idea of prioritizing distant suburbs falls a bit flat when considering the evening counter commute. The idea does hold somewhat for morning rush hour as on ramp meters do prioritize the speed of existing traffic. Regardless, the rate limiting is the purpose. Though, why are we talking about on ramp meters when the article is not about on ramp meters? > This doesn't happen because everyone understands that those merging onto the highway are moving fast and running out of space, and prudence dictates that you slow down to make space Merging traffic should be matching, not exceeding traffic speed. Existing traffic should _speed up_ to facilitate merging. The merging cars merge behind, not in front when cars are side by side. If a merging car does not get space, then they either slow, stop, or shoulder drive. A person might slow to facilitate a merging car that is well ahead of them. Generally that right hand lane should start opening gaps between every car to facilitate a zipper merge. If side by side, the traffic that has space, the existing traffic, should speed up to make space behind and to maintain traffic speeds. If they can't speed up, then there is overall congestion, gap size shrinks and traffic speed slows..
- calfuris 2y ago
  Metering traffic turns clumped up platoons into evenly spaced vehicles, which is exactly what you don't want to see as a driver trying to turn onto a major road. Broadly spaced platoons are much better because the space between platoons is much more likely to be large enough to allow you to safely maneuver onto or across the road.
015a 2y ago
You'll notice this quickly in cities with large numbers of roundabouts. Overall and on average traffic is absolutely faster, flows better, and is safer; but in times of high volume you can find yourself in situations where you're sitting at a left turn onto the stretch of road between two roundabouts totally unable to enter traffic because its flowing so smoothly and evenly. Phrased another way, and leaning on some intuition rather than hard data: large deployments of roundabouts seem to very well optimize travel times and safety for 95% of cars, but make the situation much worse for the remaining 5% (not to mention for pedestrians; my intuition as a pedestrian & cyclist in one of these cities is that I'd much, much rather cross signaled intersections when on foot; roundabouts are hyper-optimized for cars and hell for those not in one).
- RaftPeople 2y ago
  I was in London a looong time ago and for some high volume roundabouts (I think they were a little outside of the city) they had stop lights in conjunction with the roundabout to solve this exact problem.
- judge2020 2y ago
  Carmel, Indiana is nearly _all_ roundabouts, and pedestrians/cyclists do well relative to other US cities because the crossing distances are short and cars speeds are slower. https://www.carmel.in.gov/government/departments-services/engineering/roundabouts https://www.carmel.in.gov/government/departments-services/en... https://www.iihs.org/topics/roundabouts https://www.iihs.org/topics/roundabouts (ctrl f pedestrian)
- bugbuddy 2y ago
  Whatabout roundabouts with pedestrianlights?
  - xeromal 2y ago
    I've never seen those before. Does that mean the roundabout has redlights at every entrance
    - 2y ago
bitshiftfaced 2y ago
I imagine there's room for optimization within the constraints of needing spaces in traffic.
- QuarterReptile 2y ago
  I would expect so. My intention was to remind or inform that delays are part of the goal. In other words, we may get some time back, but plan on it being less than you would like.
SoftTalker 2y ago
Some cities also do it deliberately, as they want to make driving a car as undesireable as possible, and they hope you'll start using one of the bike lanes that they spent a lot of money building but that nobody uses.
nadermx 2y ago
Book called Killed by a Traffic Engineer talks about this

cvoss 2y ago

This is very true. I routinely depend on stop lights to govern intersections other than the intersection the light is posted at. And when I'm sitting at a red light with a bunch of other people, complaining to myself about how inefficient it seems because there is currently no cross traffic, I have to remind myself we are helping people downstream from the intersection to enter the road.

cowsaymoo 2y ago
cognitive behavioral therapy enjoyer:

smilekzs 2y ago

The goal you described matches more of an on-ramp meter instead of surface street lights? Unless of course we're talking about an intersection leading to the on-ramp, but now we're into back-off effects as well, which arguably could use more smartness in their schedule.

QuarterReptile 2y ago
It's sort of the reverse, in a sense. If drivers adhered strictly to yield signs, those getting onto the highway would wait until there was a space in traffic. There would be times when you could not get on to the highway at all, when traffic was heavy but not so heavy that it slowed. To solve this (again, with strictly following RoW), you would have to either slow speeds on the highway or put stop lights on the highway to let mergers enter the roadway. This doesn't happen because everyone understands that those merging onto the highway are moving fast and running out of space, and prudence dictates that you slow down to make space, rather than finding out if you're driving next to someone who will crash into you. At the far end of the spectrum from that situation, you have people waiting forever to cross, in a marked crossing where they have right of way, because they're stopped (the status quo supports them not going) and they stand to die if the driver doesn't yield properly. Fast unlimited-access roads are somewhere in the middle: the mergers don't have the initiative, but the suffering is more evenly distributed in the case of a crash, so the passing drivers are perhaps more prepared to slam on brakes. The on-ramp meters provide the service of prioritizing drivers from distant suburbs or out of town at the expense of those who dwell in nearer suburbs. To put a different spin on it, they slightly disincentivize short trips on highways.
- seadan83 2y ago
  I have trouble agreeing. > There would be times when you could not get on to the highway at all, when traffic was heavy but not so heavy that it slowed. The flowing traffic makes space for the merging traffic, which also takes up any existing gaps. The merging traffic ideally zipper merges at traffic speed. Traffic speed is correlated to gaps between cars. If merging gets tight, gap size is small, traffic is therefore going slower. If merging is impossible, then gap size is tiny, traffic speed is approaching zero, and both the onramp and highway are a traffic jam. It is the accumulation of new traffic that slows traffic speed. I think you are implying traffic speed remains a fixed constant and merging traffic just waits. Instead there is an interplay. Which comes to onramp lights. That is just a rate limiter to avoid the highway from going into an extreme bottleneck. The highway capacity is the bottleneck, so adding more traffic to it freely makes it exponentially worse. It is not at all about incentives but preservation of traffic flow. The idea of prioritizing distant suburbs falls a bit flat when considering the evening counter commute. The idea does hold somewhat for morning rush hour as on ramp meters do prioritize the speed of existing traffic. Regardless, the rate limiting is the purpose. Though, why are we talking about on ramp meters when the article is not about on ramp meters? > This doesn't happen because everyone understands that those merging onto the highway are moving fast and running out of space, and prudence dictates that you slow down to make space Merging traffic should be matching, not exceeding traffic speed. Existing traffic should _speed up_ to facilitate merging. The merging cars merge behind, not in front when cars are side by side. If a merging car does not get space, then they either slow, stop, or shoulder drive. A person might slow to facilitate a merging car that is well ahead of them. Generally that right hand lane should start opening gaps between every car to facilitate a zipper merge. If side by side, the traffic that has space, the existing traffic, should speed up to make space behind and to maintain traffic speeds. If they can't speed up, then there is overall congestion, gap size shrinks and traffic speed slows..
calfuris 2y ago
Metering traffic turns clumped up platoons into evenly spaced vehicles, which is exactly what you don't want to see as a driver trying to turn onto a major road. Broadly spaced platoons are much better because the space between platoons is much more likely to be large enough to allow you to safely maneuver onto or across the road.

015a 2y ago

You'll notice this quickly in cities with large numbers of roundabouts. Overall and on average traffic is absolutely faster, flows better, and is safer; but in times of high volume you can find yourself in situations where you're sitting at a left turn onto the stretch of road between two roundabouts totally unable to enter traffic because its flowing so smoothly and evenly. Phrased another way, and leaning on some intuition rather than hard data: large deployments of roundabouts seem to very well optimize travel times and safety for 95% of cars, but make the situation much worse for the remaining 5% (not to mention for pedestrians; my intuition as a pedestrian & cyclist in one of these cities is that I'd much, much rather cross signaled intersections when on foot; roundabouts are hyper-optimized for cars and hell for those not in one).

RaftPeople 2y ago
I was in London a looong time ago and for some high volume roundabouts (I think they were a little outside of the city) they had stop lights in conjunction with the roundabout to solve this exact problem.
judge2020 2y ago
Carmel, Indiana is nearly _all_ roundabouts, and pedestrians/cyclists do well relative to other US cities because the crossing distances are short and cars speeds are slower. https://www.carmel.in.gov/government/departments-services/engineering/roundabouts https://www.carmel.in.gov/government/departments-services/en... https://www.iihs.org/topics/roundabouts https://www.iihs.org/topics/roundabouts (ctrl f pedestrian)
bugbuddy 2y ago
Whatabout roundabouts with pedestrianlights?
- xeromal 2y ago
  I've never seen those before. Does that mean the roundabout has redlights at every entrance
  - 2y ago

bitshiftfaced 2y ago

I imagine there's room for optimization within the constraints of needing spaces in traffic.

QuarterReptile 2y ago
I would expect so. My intention was to remind or inform that delays are part of the goal. In other words, we may get some time back, but plan on it being less than you would like.

SoftTalker 2y ago

Some cities also do it deliberately, as they want to make driving a car as undesireable as possible, and they hope you'll start using one of the bike lanes that they spent a lot of money building but that nobody uses.

nadermx 2y ago

Book called Killed by a Traffic Engineer talks about this