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Some intersections have a sensor under the asphalt to detect a vehicle and sequence a light transition, and its not a new technology

by rdn 2y ago

jamiesonbecker 2y ago
That's not what the article is talking about.
mrandish 2y ago
Yes, this intersection has that. The problem is the sensor starts a timer that's set to 2 or 3 minutes for most of the day. This becomes a minimum wait time even when there are no oncoming cars for the entire wait period. At this intersection, the wastefully pointless "idle there for 3 minutes with no other cars anywhere in sight" scenario happens quite often. There's also an even more perverse failure mode: we often end up waiting for 2.5 minutes with no other cars anywhere in sight, then when a lone car is randomly approaching the light that's been green for no cars (going its way) for 2.5 minutes, that one car gets stopped and waits as we finally get our turn arrow after 3 minutes. If the light was the least bit "smart", it would have changed for us right when we pulled up and no other cars were in sight. The turn arrow is only 10 seconds, so we would have been long gone and the intersection back to green by the time that other car was approaching - no car would have needed to wait and everyone would have been better served.
- hanszarkov 2y ago
  I have experienced the same thing 100 plus times
- Filligree 2y ago
  There's a few intersections like that here in Dublin. But they aren't marked. So what sometimes happens is I cruise up on a bike, in the middle of the road because none of those have bike lanes.. and the bike, naturally, never triggers the lights. Neither does the car behind me.
  - doubled112 2y ago
    I used to make note of these and run up to push the pedestrian crossing button if there was one. It is the only way the system will realize you are waiting.
  - mrandish 2y ago
    Sorry to hear it's not only a problem here in the U.S. Ideally, our intersection wouldn't have dedicated left turn arrows at all, since it doesn't need them most of the day. The problem arises only about four hours a day. At those times the otherwise empty thoroughfare turns into a wave of cars making it impossible to enter or leave our neighborhood street by turning left because there's rarely a large enough gap in the fast-flowing traffic. Traffic engineers probably have a term for this kind of bi-polar intersection. A solution would be some kind of "conditional left arrow" but there's no such thing (at least here in the U.S.) If there's a dedicated green arrow for left turn, then there's a modal left-turn red arrow along with it. It should be possible to improve all scenarios by standardizing something like a flashing yellow arrow to mean "okay to cross if no oncoming traffic" since this already works as the default behavior at intersections with no lights or lights with no left turn arrows.
    - Filligree 2y ago
      There's no left arrow? The sole traffic lights just never turn green.
    - rootusrootus 2y ago
      > flashing yellow arrow to mean "okay to cross if no oncoming traffic" That's already a thing, unless I'm misunderstanding you. We've had flashing yellow left turn arrows for years. I'm in the PNW, but I've seen it in other places in the US, we're definitely not unique.
- xattt 2y ago
  My local municipality decided that it would be more appropriate for lights to flash yellow and/or red on a couple of low-traffic intersections along major routes between 11 PM and 6 AM.
  - mrandish 2y ago
    I've seen that some places as well but I haven't seen it done in the daytime for some reason.
    - PaulHoule 2y ago
      https://usa.streetsblog.org/2018/10/30/for-a-more-walkable-city-replace-signals-with-all-way-stops https://usa.streetsblog.org/2018/10/30/for-a-more-walkable-c...
  - ghaff 2y ago
    I have a few intersections near me that desperately needed to have the lights added but only for busy times of day. At night it can take 5 minutes to get through a battery of lights even with virtually no traffic. I suspect choosing not to flash them at night is some combination of people not really familiar with that system getting potentially confused and (these are somewhat complex intersections) others just getting careless rather than carefully checking, at night, all the directions that traffic could be coming from.
    - prmoustache 2y ago
      That is the beauty of roundabouts, they work regardless of the time of day, and on some where there is a need for more regulation you can still add lights before the roundabout.
      - ghaff 2y ago
        The lights near me were to tame chaos at an existing intersection. A big roundabout I use semi-regularly does indeed handle 4 busy roads coming together well at night even if it’s a nightmare at rush hour.
- WalterBright 2y ago
  > the wastefully pointless "idle there for 3 minutes with no other cars anywhere in sight" scenario happens quite often. The climate activists should be focused on solving that problem.
  - mrandish 2y ago
    While the potential of super-smart AI to improve transport efficiency, costs and environmental impact with self-driving is obvious, it's also expensive and still many years from being ready for broad deployment. It's puzzling that low-hanging fruit like an AI-assisted "Slightly Smarter" traffic light is ignored. It could deliver meaningful improvement today with cheap, easy to retrofit, Raspberry Pi-level tech which already works well enough for a simple, limited use case like reducing unnecessary idling at traffic lights.
    - jerezzprime 2y ago
      For this situation, and similar ones, there are simple solutions. For example, in this situation, the timer should always be running (and resets when the light changes). When a car triggers the sensor, the light should change if the timer is > N. If the timer is not there yet, wait until timer is N. No AI required, just basic thoughtfulness and requirements gathering.
      - WalterBright 2y ago
        The trouble with the street sensors is that your car has to come to a stop before it is detected. Stopping and starting cars consumes a great deal of gasoline. Contrast it with the flow achieved when there's a traffic cop managing an intersection. It's an enormous improvement.
    - deleted 2y ago
      [deleted]
  - darby_eight 2y ago
    ? Is this a joke
quickthrowman 2y ago
https://en.m.wikipedia.org/wiki/Induction_loop https://en.m.wikipedia.org/wiki/Induction_loop

Some intersections have a sensor under the asphalt to detect a vehicle and sequence a light transition, and its not a new technology

by rdn 2y ago

Some intersections have a sensor under the asphalt to detect a vehicle and sequence a light transition, and its not a new technology

jamiesonbecker 2y ago

That's not what the article is talking about.

mrandish 2y ago

Yes, this intersection has that. The problem is the sensor starts a timer that's set to 2 or 3 minutes for most of the day. This becomes a minimum wait time even when there are no oncoming cars for the entire wait period. At this intersection, the wastefully pointless "idle there for 3 minutes with no other cars anywhere in sight" scenario happens quite often. There's also an even more perverse failure mode: we often end up waiting for 2.5 minutes with no other cars anywhere in sight, then when a lone car is randomly approaching the light that's been green for no cars (going its way) for 2.5 minutes, that one car gets stopped and waits as we finally get our turn arrow after 3 minutes. If the light was the least bit "smart", it would have changed for us right when we pulled up and no other cars were in sight. The turn arrow is only 10 seconds, so we would have been long gone and the intersection back to green by the time that other car was approaching - no car would have needed to wait and everyone would have been better served.

hanszarkov 2y ago
I have experienced the same thing 100 plus times
Filligree 2y ago
There's a few intersections like that here in Dublin. But they aren't marked. So what sometimes happens is I cruise up on a bike, in the middle of the road because none of those have bike lanes.. and the bike, naturally, never triggers the lights. Neither does the car behind me.
- doubled112 2y ago
  I used to make note of these and run up to push the pedestrian crossing button if there was one. It is the only way the system will realize you are waiting.
- mrandish 2y ago
  Sorry to hear it's not only a problem here in the U.S. Ideally, our intersection wouldn't have dedicated left turn arrows at all, since it doesn't need them most of the day. The problem arises only about four hours a day. At those times the otherwise empty thoroughfare turns into a wave of cars making it impossible to enter or leave our neighborhood street by turning left because there's rarely a large enough gap in the fast-flowing traffic. Traffic engineers probably have a term for this kind of bi-polar intersection. A solution would be some kind of "conditional left arrow" but there's no such thing (at least here in the U.S.) If there's a dedicated green arrow for left turn, then there's a modal left-turn red arrow along with it. It should be possible to improve all scenarios by standardizing something like a flashing yellow arrow to mean "okay to cross if no oncoming traffic" since this already works as the default behavior at intersections with no lights or lights with no left turn arrows.
  - Filligree 2y ago
    There's no left arrow? The sole traffic lights just never turn green.
  - rootusrootus 2y ago
    > flashing yellow arrow to mean "okay to cross if no oncoming traffic" That's already a thing, unless I'm misunderstanding you. We've had flashing yellow left turn arrows for years. I'm in the PNW, but I've seen it in other places in the US, we're definitely not unique.
xattt 2y ago
My local municipality decided that it would be more appropriate for lights to flash yellow and/or red on a couple of low-traffic intersections along major routes between 11 PM and 6 AM.
- mrandish 2y ago
  I've seen that some places as well but I haven't seen it done in the daytime for some reason.
  - PaulHoule 2y ago
    https://usa.streetsblog.org/2018/10/30/for-a-more-walkable-city-replace-signals-with-all-way-stops https://usa.streetsblog.org/2018/10/30/for-a-more-walkable-c...
- ghaff 2y ago
  I have a few intersections near me that desperately needed to have the lights added but only for busy times of day. At night it can take 5 minutes to get through a battery of lights even with virtually no traffic. I suspect choosing not to flash them at night is some combination of people not really familiar with that system getting potentially confused and (these are somewhat complex intersections) others just getting careless rather than carefully checking, at night, all the directions that traffic could be coming from.
  - prmoustache 2y ago
    That is the beauty of roundabouts, they work regardless of the time of day, and on some where there is a need for more regulation you can still add lights before the roundabout.
    - ghaff 2y ago
      The lights near me were to tame chaos at an existing intersection. A big roundabout I use semi-regularly does indeed handle 4 busy roads coming together well at night even if it’s a nightmare at rush hour.
WalterBright 2y ago
> the wastefully pointless "idle there for 3 minutes with no other cars anywhere in sight" scenario happens quite often. The climate activists should be focused on solving that problem.
- mrandish 2y ago
  While the potential of super-smart AI to improve transport efficiency, costs and environmental impact with self-driving is obvious, it's also expensive and still many years from being ready for broad deployment. It's puzzling that low-hanging fruit like an AI-assisted "Slightly Smarter" traffic light is ignored. It could deliver meaningful improvement today with cheap, easy to retrofit, Raspberry Pi-level tech which already works well enough for a simple, limited use case like reducing unnecessary idling at traffic lights.
  - jerezzprime 2y ago
    For this situation, and similar ones, there are simple solutions. For example, in this situation, the timer should always be running (and resets when the light changes). When a car triggers the sensor, the light should change if the timer is > N. If the timer is not there yet, wait until timer is N. No AI required, just basic thoughtfulness and requirements gathering.
    - WalterBright 2y ago
      The trouble with the street sensors is that your car has to come to a stop before it is detected. Stopping and starting cars consumes a great deal of gasoline. Contrast it with the flow achieved when there's a traffic cop managing an intersection. It's an enormous improvement.
  - deleted 2y ago
    [deleted]
- darby_eight 2y ago
  ? Is this a joke

quickthrowman 2y ago

https://en.m.wikipedia.org/wiki/Induction_loop https://en.m.wikipedia.org/wiki/Induction_loop