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Lights seem incredibly inefficient to me. How many times have I been driving towards a green at the speed limit and it turns yellow just in time to force me to

Lights seem incredibly inefficient to me. How many times have I been driving towards a green at the speed limit and it turns yellow just in time to force me to slam on the brakes or the gas pedal, all to let one waiting car go? Why not detect my coming and wait for an efficient yellow timing, thus I am not wasting gas and braking unnecessarily? This would substantially improve carbon emissions and brake dust, yet dozens of times per month, I see lights inefficiently block traffic unnecessarily.

lunias 7y ago
Agreed. The traffic light paradigm that I've seen popping up more often (which really bothers me) is the red left turn arrow. Light's green, no oncoming traffic; but can't make a very safe left because there's a red arrow staring back at me.
- C1sc0cat 7y ago
  This where you need filter signals
- dsfyu404ed 7y ago
  A red left arrow is just the state/municipality telling you you're too stupid to make the decision yourself. I'm a big fan of the "green for a few seconds then flashing yellow" arrow.
  - lunias 7y ago
    Seems like the only possible reason to me... sadly we live in a society that caters to the lowest common denominator rather than demanding and rewarding excellence. I worry for future generations. When I lived in Tucson AZ almost every light was set up for lagging left turns. Where you can go when it's safe, but in the event of heavy traffic you'd be able to count on having a green arrow to empty the left turn lane - worked great!
    - magduf 7y ago
      >sadly we live in a society that caters to the lowest common denominator rather than demanding and rewarding excellence You can't demand and reward excellence with car driving, because by assuming that people are all highly competent, you'll end up with lots of fatal crashes because of all the people who aren't competent. You can only assume car drivers are competent in societies where there's plenty of options for people who don't or can't drive, and America made the decision to not be such a society, so everyone has to be able to drive, even if they're an idiot.
      - lunias 7y ago
        I don't think that we have to assume competence when we have a system in place for issuing licenses, but you do have a point about people needing access to transportation. I do believe that any real solution would have to provide reasonable alternatives for people who do not meet the requirements. I also don't feel like the bar has to be raised much with regard to the licensing, but currently (and I believe knowledge of this to be reflected in some patterns of traffic control) the bar is clear-able by all with little to no competence check.
        magduf 7y ago
        >I do believe that any real solution would have to provide reasonable alternatives for people who do not meet the requirements. Sorry, but that's completely impossible. You simply cannot have a spread-out, car-based society with "reasonable alternatives" for people who can't drive, unless perhaps you're going to heavily subsidize Uber and Lyft. Buses and trains don't work well in suburbs; trains only make sense with enough density to have enough ridership, and buses only make sense to fill in where train lines don't exist. In the suburbs, people stuck taking the bus get penalized with ridiculously long transit times, because the bus takes a long, circuitous route, only comes once or twice an hour, etc. That isn't a "reasonable alternative" when people with a car get get there in 10 minutes or less. So you have two choices: a society like Germany's where at least in urban areas it's easy to get around without a car, and then you can have a very high competency requirement for car drivers; or a society like America's, where the whole society is designed for cars (except for a small handful of urban cores) and you have to have a car to achieve a middle-class existence, so you cannot have a high competency requirement because otherwise you are restricting peoples' right to movement and travel.
- ken 7y ago
  Explanation, for those who don’t understand the problem: in some states, like New York, a red arrow is different than a red circle in that it prohibits turn-on-red. In other states, like Washington, the red arrow is equivalent to the red circle. We even have left-turn-on-red, so (unless you’re stuck behind an out-of-towner) this tends to be much less of an issue.
  - WorldMaker 7y ago
    The variety in individual state traffic light rules is fascinating, and something that certainly doesn't help for US travelers. Some states are left-turn-on-red, others are not, telling which is which is not always obvious. (For instance, Kentucky is no left-turn-on-red [either red arrow or full red; mostly the state doesn't use red arrows because they'd be redundant in that case], but allows for left-turn-may-yield on flashing yellow/amber.)
  - andrewmunsell 7y ago
    For those Washingtonians that didn't know about left-on-red (I didn't before a couple weeks ago), you can turn left on red (or a red arrow) as long as it's from a one- or two-way street onto a one-way street (or freeway on-ramp), after a stop and if it's clear. https://devblogs.microsoft.com/oldnewthing/20181101-01/?p=100115 https://devblogs.microsoft.com/oldnewthing/20181101-01/?p=10... https://app.leg.wa.gov/rcw/default.aspx?cite=46.61.055 https://app.leg.wa.gov/rcw/default.aspx?cite=46.61.055 I've never done it myself and don't intend to start since I think it's a bit obscure and I don't want to argue with a cop about it if I get pulled over.
- fma 7y ago
  For this scenario, I've seen new lights have the left turn arrow blinks. It lets you know you can turn left if it's safe to do so. It took a while to get used to because in the past there simply just won't be any signal, to imply you can go if you want.
  - lilott8 7y ago
    I've really loathed my time driving in socal coming from the midwest. The idea that I cannot turn left on green is one of the more appalling "features" of traffic management here (the way the lights work, in general is abhorrent). But slowly, throughout socal, I've seen the flashing yellow left-turn arrow; a subtle change to the UX that I think is brilliant and should be adopted everywhere.
  - bradstewart 7y ago
    They've started putting these (blinking yellow arrows for non-protected left turns) all over Austin. Confused the heck out of me at first as well.
- CaliforniaKarl 7y ago
  If I remember correctly, in Southern California, some intersections have an additional left-turn arrow which flashes yellow, indicating that you may make the left turn if there is no oncoming traffic. It's a separate light to make the flashing-yellow to solid-yellow transition clearer.
- triceratops 7y ago
  Ontario solves that by having there be a left green arrow + regular green light. The left green arrow indicates a protected left but you are also free to make an unprotected left on the regular green light, once the left green is off.
  - toomanybeersies 7y ago
    Australia and New Zealand have the same (except on the right turn arrow because we drive on the left). I always thought this was normal. If the right turn arrow is green you have right of way, if it's red you must stop, and if it's not illuminated you give way to oncoming traffic and turn when safe.
C1sc0cat 7y ago
Amber is prepare to stop not an instruction to do a crash stop from my memoires of the UK highway code. I.e. if you at or very close to the line you prepare to stop but if your very close you proceed carefully and make the turn.
- vinay427 7y ago
  In most countries, if you cross the line or enter the intersection while the light that applies to you is red, it is a violation. This means that unless the yellow light is long enough to account for approaching drivers' reaction times/distances and braking times/distances it can result in crash stops. Many lights in every country I've driven in have an insufficient yellow-light period given these considerations.
  - jtbayly 7y ago
    And jurisdictions with auto-ticketing based on red-light cameras shorten the yellow light, driving up income by making it very hard to avoid running a (barely) red light.
    - seszett 7y ago
      That doesn't seem true, France for example has automatic cameras at traffic lights, and the yellow light has a duration fixed by law (3s on urban streets, 5s outside cities) and it has not changed since traffic light cameras were introduced. So that's one jurisdiction where your assertion is false. (Anyway, in most places the fines from the automatic cameras do not go to the same administration that decides the speed limits and places the traffic lights, so in the end the common accusation of "they only want to make money from it" doesn't make that much sense)
      - jtbayly 7y ago
        I didn't state that it was universal. It does happen to be true. You can look it up. There are even links elsewhere in this thread. Last I read about it was some time ago, but I doubt it has been fixed.
imglorp 7y ago
> Why not detect my coming This bugs me. $50 of hardware can accomplish this, today. Raspi running vehicle detection code. If something is coming and the other way is clear, why not flip the intersection before it arrives?
- lm28469 7y ago
  > $50 of hardware can accomplish this, today. Raspi running vehicle detection code. $50 * 300 000 (quick google search about the number of traffic light in the US), That's not taking into account installation and regular maintenance.
  - clairity 7y ago
    $1.5M (maybe 3X that with other costs) is literally a rounding error for the US federal budget: expenditures are $4.4T and revenue is $3.4T (that $1T/yr deficit is maddening btw).
    - mcguire 7y ago
      How long would it take you to install a traffic light camera system? Would you do that for $100?
      - imglorp 7y ago
        It's probably easier to install than the typical sensor loop under the asphalt. The camera and cpu could be on the same circuit board as one of the LED lens units, which are already sealed units heated against snow. It would need an additional comm line down to the controller from each light head, which might just be a cable pull through conduit.
        lm28469 7y ago
        Besides being weather proof it would also need to be theft proof. It would also probably have to pass some sort of certification(s) as it would control traffic lights which could be dangerous in case of malfunctions, regular tests, &c. I'm all for optimising things but sometimes it's just not worth the hassle. A well timed orange light is good enough.
Kudos 7y ago
You can't always do this with current traffic planning. In busier areas you have to consider throughput at _other_ junctions and not just the immediate one. Changing one light's timing could make zero difference to that junction, but could totally screw up traffic flow downstream of it.
- uoaei 7y ago
  Your point is valid but isn't really a counterargument to what OP said. There is a balance to be struck. Some sort of half-local/half-global optimization algorithm running in the "smart grid" would be a good idea.
  - deleted 7y ago
    [deleted]
  - TheGallopedHigh 7y ago
    Optimizing traffic flow is major area of research in academia. Dresden has a full group dedicated to it
throwaway66920 7y ago
It shouldn’t. Yellow lights are supposed to last an amount of time based on the speed limit at that section so this doesn’t happen. Traffic simulations are generally quite complex. In your proposal, if your approach is not detected correctly, you either stop traffic for a car which isn’t there, or you never stop traffic for a car which is there.
- ken 7y ago
  I would love to learn more about traffic simulations they use. I saw some software traffic simulators in college and they looked nice but in no way included real-world driving. It’s hard to imagine, given how bad traffic is, that our streets were planned by sophisticated computer simulations. There’s one place near me where it can take nearly an hour to go 3 blocks during rush hour, due to people blocking the box. Do simulations take that into account?
  - magduf 7y ago
    As I've said before, I think traffic engineering is probably the most intellectually dishonest profession there is, at least in America.
    - abduhl 7y ago
      Oh man wait until you learn about machine learning where they don’t even have a real world result to compare it to
      - throwaway66920 7y ago
        You mean... unsupervised machine learning? That doesn’t feel intellectually dishonest to me
lm28469 7y ago
> Why not detect my coming and wait for an efficient yellow timing, thus I am not wasting gas and braking unnecessarily? At that scale trying to do anything clever will cost billions. Most red lights don't even detect motorcycles standing right on top of their sensor, we're decades away from smart lights detecting your car speed/distance and computing the most optimised yellow light timing. Also, in most cases you should be able to roll off the throttle and coast to the light without having to aggressively brake. If it's not the case the yellow light is not timed well and you can contact the company handling the roadwork in your city.
garaetjjte 7y ago
Sometimes there are countdown timers displaying time to red/green change. I don't know why they aren't deployed more widely, they are very convenient.
- Y-bar 7y ago
  There have been research showing that while a majority of people who sit in an intersection with timers appreciate them… It also increases the number of accidents because people spend too much attention to the timer and fail to look at the environment whether or not it is safe to accelerate. There is also evidence that suggest that countdown timers from green to red cause more drivers to accelerate and increase the risk of accidents there as well.
bjourne 7y ago
Sorry for stating the obvious, but.. if you have to slam on the brakes when approaching an intersection, you are driving too fast. :)
- tomohawk 7y ago
  This may or may not be true. In one of the areas near us, they installed red light cameras and had short yellows. You'd be on a 55mph road and get a 2-3 second yellow. Slamming on the brakes or running the red were the 2 options. With a 4 second yellow (which is actually state law), you can come to a normal stop. You could fight your ticket in court, but you had to prove the yellow was short. The state highway department had equipment you could use to time the light to prove your case. Time consuming, but doable if you didn't have a job or were retired. If you did that, you would get off, but they would still not change the light. Pretty ridiculous.
  - Gibbon1 7y ago
    I think California changed the law, so it's legal to enter on the yellow. If it changes to red doesn't matter. However you can't block the box either. That was specifically to prevent muni's from shortening the yellow to generate revenue.
  - bjourne 7y ago
    But do you have to drive at the posted limit? Even if the yellow time was 4 seconds, 55 mph (90 kmh) gives you almost no margin of error.
    - Dylan16807 7y ago
      Suggesting that the speed limit is "driving too fast :)" in good weather is ridiculous. If there is a problem, it is completely on the yellow light.
      - bjourne 7y ago
        Then perhaps, if drivers are unwilling to consider obstacles on the road, the speed limit should be lowered.
habnds 7y ago
driving is incredibly inefficient, lights are just a small part of it
m3at 7y ago
Not for individual car owners, but in Japan some buses connect with neighboring signals which are more likely to turn green when the buses are approaching. Having buses usually quite close to schedule probably helps
r00fus 7y ago
Traffic circles / roundabouts (for smaller intersections) are better. I wonder how mass adoption might impact air quality and fuel efficiency.
deftturtle 7y ago
My solution is to have a blinking green, which indicates that it’s about to turn yellow. We might also lengthen the yellow duration, but knowing that the light will switch gives time to decide if you can speed up or decelerate safely, without wasting energy. I’d be very curious to see how a blinking green system plays out in tests. Another thought: if we manage traffic like regulating fluid flow and pressure, we could avoid situations where a single car exiting a parking lot shuts down the highway instantly. That single car should have to wait maybe 5-10 seconds before triggering the lights, and the blinking green would let highway drivers adjust. Forcing 20 cars to rapidly stop for an already stopped car makes no sense. As the single car waits, pressure “builds” so to speak, and eventually the light decides that the fluid flow should change.

lunias 7y ago

Agreed. The traffic light paradigm that I've seen popping up more often (which really bothers me) is the red left turn arrow. Light's green, no oncoming traffic; but can't make a very safe left because there's a red arrow staring back at me.

C1sc0cat 7y ago
This where you need filter signals
dsfyu404ed 7y ago
A red left arrow is just the state/municipality telling you you're too stupid to make the decision yourself. I'm a big fan of the "green for a few seconds then flashing yellow" arrow.
- lunias 7y ago
  Seems like the only possible reason to me... sadly we live in a society that caters to the lowest common denominator rather than demanding and rewarding excellence. I worry for future generations. When I lived in Tucson AZ almost every light was set up for lagging left turns. Where you can go when it's safe, but in the event of heavy traffic you'd be able to count on having a green arrow to empty the left turn lane - worked great!
  - magduf 7y ago
    >sadly we live in a society that caters to the lowest common denominator rather than demanding and rewarding excellence You can't demand and reward excellence with car driving, because by assuming that people are all highly competent, you'll end up with lots of fatal crashes because of all the people who aren't competent. You can only assume car drivers are competent in societies where there's plenty of options for people who don't or can't drive, and America made the decision to not be such a society, so everyone has to be able to drive, even if they're an idiot.
    - lunias 7y ago
      I don't think that we have to assume competence when we have a system in place for issuing licenses, but you do have a point about people needing access to transportation. I do believe that any real solution would have to provide reasonable alternatives for people who do not meet the requirements. I also don't feel like the bar has to be raised much with regard to the licensing, but currently (and I believe knowledge of this to be reflected in some patterns of traffic control) the bar is clear-able by all with little to no competence check.
      - magduf 7y ago
        >I do believe that any real solution would have to provide reasonable alternatives for people who do not meet the requirements. Sorry, but that's completely impossible. You simply cannot have a spread-out, car-based society with "reasonable alternatives" for people who can't drive, unless perhaps you're going to heavily subsidize Uber and Lyft. Buses and trains don't work well in suburbs; trains only make sense with enough density to have enough ridership, and buses only make sense to fill in where train lines don't exist. In the suburbs, people stuck taking the bus get penalized with ridiculously long transit times, because the bus takes a long, circuitous route, only comes once or twice an hour, etc. That isn't a "reasonable alternative" when people with a car get get there in 10 minutes or less. So you have two choices: a society like Germany's where at least in urban areas it's easy to get around without a car, and then you can have a very high competency requirement for car drivers; or a society like America's, where the whole society is designed for cars (except for a small handful of urban cores) and you have to have a car to achieve a middle-class existence, so you cannot have a high competency requirement because otherwise you are restricting peoples' right to movement and travel.
ken 7y ago
Explanation, for those who don’t understand the problem: in some states, like New York, a red arrow is different than a red circle in that it prohibits turn-on-red. In other states, like Washington, the red arrow is equivalent to the red circle. We even have left-turn-on-red, so (unless you’re stuck behind an out-of-towner) this tends to be much less of an issue.
- WorldMaker 7y ago
  The variety in individual state traffic light rules is fascinating, and something that certainly doesn't help for US travelers. Some states are left-turn-on-red, others are not, telling which is which is not always obvious. (For instance, Kentucky is no left-turn-on-red [either red arrow or full red; mostly the state doesn't use red arrows because they'd be redundant in that case], but allows for left-turn-may-yield on flashing yellow/amber.)
- andrewmunsell 7y ago
  For those Washingtonians that didn't know about left-on-red (I didn't before a couple weeks ago), you can turn left on red (or a red arrow) as long as it's from a one- or two-way street onto a one-way street (or freeway on-ramp), after a stop and if it's clear. https://devblogs.microsoft.com/oldnewthing/20181101-01/?p=100115 https://devblogs.microsoft.com/oldnewthing/20181101-01/?p=10... https://app.leg.wa.gov/rcw/default.aspx?cite=46.61.055 https://app.leg.wa.gov/rcw/default.aspx?cite=46.61.055 I've never done it myself and don't intend to start since I think it's a bit obscure and I don't want to argue with a cop about it if I get pulled over.
fma 7y ago
For this scenario, I've seen new lights have the left turn arrow blinks. It lets you know you can turn left if it's safe to do so. It took a while to get used to because in the past there simply just won't be any signal, to imply you can go if you want.
- lilott8 7y ago
  I've really loathed my time driving in socal coming from the midwest. The idea that I cannot turn left on green is one of the more appalling "features" of traffic management here (the way the lights work, in general is abhorrent). But slowly, throughout socal, I've seen the flashing yellow left-turn arrow; a subtle change to the UX that I think is brilliant and should be adopted everywhere.
- bradstewart 7y ago
  They've started putting these (blinking yellow arrows for non-protected left turns) all over Austin. Confused the heck out of me at first as well.
CaliforniaKarl 7y ago
If I remember correctly, in Southern California, some intersections have an additional left-turn arrow which flashes yellow, indicating that you may make the left turn if there is no oncoming traffic. It's a separate light to make the flashing-yellow to solid-yellow transition clearer.
triceratops 7y ago
Ontario solves that by having there be a left green arrow + regular green light. The left green arrow indicates a protected left but you are also free to make an unprotected left on the regular green light, once the left green is off.
- toomanybeersies 7y ago
  Australia and New Zealand have the same (except on the right turn arrow because we drive on the left). I always thought this was normal. If the right turn arrow is green you have right of way, if it's red you must stop, and if it's not illuminated you give way to oncoming traffic and turn when safe.

C1sc0cat 7y ago

Amber is prepare to stop not an instruction to do a crash stop from my memoires of the UK highway code. I.e. if you at or very close to the line you prepare to stop but if your very close you proceed carefully and make the turn.

vinay427 7y ago
In most countries, if you cross the line or enter the intersection while the light that applies to you is red, it is a violation. This means that unless the yellow light is long enough to account for approaching drivers' reaction times/distances and braking times/distances it can result in crash stops. Many lights in every country I've driven in have an insufficient yellow-light period given these considerations.
- jtbayly 7y ago
  And jurisdictions with auto-ticketing based on red-light cameras shorten the yellow light, driving up income by making it very hard to avoid running a (barely) red light.
  - seszett 7y ago
    That doesn't seem true, France for example has automatic cameras at traffic lights, and the yellow light has a duration fixed by law (3s on urban streets, 5s outside cities) and it has not changed since traffic light cameras were introduced. So that's one jurisdiction where your assertion is false. (Anyway, in most places the fines from the automatic cameras do not go to the same administration that decides the speed limits and places the traffic lights, so in the end the common accusation of "they only want to make money from it" doesn't make that much sense)
    - jtbayly 7y ago
      I didn't state that it was universal. It does happen to be true. You can look it up. There are even links elsewhere in this thread. Last I read about it was some time ago, but I doubt it has been fixed.

imglorp 7y ago

> Why not detect my coming This bugs me. $50 of hardware can accomplish this, today. Raspi running vehicle detection code. If something is coming and the other way is clear, why not flip the intersection before it arrives?

lm28469 7y ago
> $50 of hardware can accomplish this, today. Raspi running vehicle detection code. $50 * 300 000 (quick google search about the number of traffic light in the US), That's not taking into account installation and regular maintenance.
- clairity 7y ago
  $1.5M (maybe 3X that with other costs) is literally a rounding error for the US federal budget: expenditures are $4.4T and revenue is $3.4T (that $1T/yr deficit is maddening btw).
  - mcguire 7y ago
    How long would it take you to install a traffic light camera system? Would you do that for $100?
    - imglorp 7y ago
      It's probably easier to install than the typical sensor loop under the asphalt. The camera and cpu could be on the same circuit board as one of the LED lens units, which are already sealed units heated against snow. It would need an additional comm line down to the controller from each light head, which might just be a cable pull through conduit.
      - lm28469 7y ago
        Besides being weather proof it would also need to be theft proof. It would also probably have to pass some sort of certification(s) as it would control traffic lights which could be dangerous in case of malfunctions, regular tests, &c. I'm all for optimising things but sometimes it's just not worth the hassle. A well timed orange light is good enough.

Kudos 7y ago

You can't always do this with current traffic planning. In busier areas you have to consider throughput at _other_ junctions and not just the immediate one. Changing one light's timing could make zero difference to that junction, but could totally screw up traffic flow downstream of it.

uoaei 7y ago
Your point is valid but isn't really a counterargument to what OP said. There is a balance to be struck. Some sort of half-local/half-global optimization algorithm running in the "smart grid" would be a good idea.
- deleted 7y ago
  [deleted]
- TheGallopedHigh 7y ago
  Optimizing traffic flow is major area of research in academia. Dresden has a full group dedicated to it

throwaway66920 7y ago

It shouldn’t. Yellow lights are supposed to last an amount of time based on the speed limit at that section so this doesn’t happen. Traffic simulations are generally quite complex. In your proposal, if your approach is not detected correctly, you either stop traffic for a car which isn’t there, or you never stop traffic for a car which is there.

ken 7y ago
I would love to learn more about traffic simulations they use. I saw some software traffic simulators in college and they looked nice but in no way included real-world driving. It’s hard to imagine, given how bad traffic is, that our streets were planned by sophisticated computer simulations. There’s one place near me where it can take nearly an hour to go 3 blocks during rush hour, due to people blocking the box. Do simulations take that into account?
- magduf 7y ago
  As I've said before, I think traffic engineering is probably the most intellectually dishonest profession there is, at least in America.
  - abduhl 7y ago
    Oh man wait until you learn about machine learning where they don’t even have a real world result to compare it to
    - throwaway66920 7y ago
      You mean... unsupervised machine learning? That doesn’t feel intellectually dishonest to me

lm28469 7y ago

> Why not detect my coming and wait for an efficient yellow timing, thus I am not wasting gas and braking unnecessarily? At that scale trying to do anything clever will cost billions. Most red lights don't even detect motorcycles standing right on top of their sensor, we're decades away from smart lights detecting your car speed/distance and computing the most optimised yellow light timing. Also, in most cases you should be able to roll off the throttle and coast to the light without having to aggressively brake. If it's not the case the yellow light is not timed well and you can contact the company handling the roadwork in your city.

garaetjjte 7y ago

Sometimes there are countdown timers displaying time to red/green change. I don't know why they aren't deployed more widely, they are very convenient.

Y-bar 7y ago
There have been research showing that while a majority of people who sit in an intersection with timers appreciate them… It also increases the number of accidents because people spend too much attention to the timer and fail to look at the environment whether or not it is safe to accelerate. There is also evidence that suggest that countdown timers from green to red cause more drivers to accelerate and increase the risk of accidents there as well.

bjourne 7y ago

Sorry for stating the obvious, but.. if you have to slam on the brakes when approaching an intersection, you are driving too fast. :)

tomohawk 7y ago
This may or may not be true. In one of the areas near us, they installed red light cameras and had short yellows. You'd be on a 55mph road and get a 2-3 second yellow. Slamming on the brakes or running the red were the 2 options. With a 4 second yellow (which is actually state law), you can come to a normal stop. You could fight your ticket in court, but you had to prove the yellow was short. The state highway department had equipment you could use to time the light to prove your case. Time consuming, but doable if you didn't have a job or were retired. If you did that, you would get off, but they would still not change the light. Pretty ridiculous.
- Gibbon1 7y ago
  I think California changed the law, so it's legal to enter on the yellow. If it changes to red doesn't matter. However you can't block the box either. That was specifically to prevent muni's from shortening the yellow to generate revenue.
- bjourne 7y ago
  But do you have to drive at the posted limit? Even if the yellow time was 4 seconds, 55 mph (90 kmh) gives you almost no margin of error.
  - Dylan16807 7y ago
    Suggesting that the speed limit is "driving too fast :)" in good weather is ridiculous. If there is a problem, it is completely on the yellow light.
    - bjourne 7y ago
      Then perhaps, if drivers are unwilling to consider obstacles on the road, the speed limit should be lowered.

habnds 7y ago

driving is incredibly inefficient, lights are just a small part of it

m3at 7y ago

Not for individual car owners, but in Japan some buses connect with neighboring signals which are more likely to turn green when the buses are approaching. Having buses usually quite close to schedule probably helps

r00fus 7y ago

Traffic circles / roundabouts (for smaller intersections) are better. I wonder how mass adoption might impact air quality and fuel efficiency.

deftturtle 7y ago

My solution is to have a blinking green, which indicates that it’s about to turn yellow. We might also lengthen the yellow duration, but knowing that the light will switch gives time to decide if you can speed up or decelerate safely, without wasting energy. I’d be very curious to see how a blinking green system plays out in tests. Another thought: if we manage traffic like regulating fluid flow and pressure, we could avoid situations where a single car exiting a parking lot shuts down the highway instantly. That single car should have to wait maybe 5-10 seconds before triggering the lights, and the blinking green would let highway drivers adjust. Forcing 20 cars to rapidly stop for an already stopped car makes no sense. As the single car waits, pressure “builds” so to speak, and eventually the light decides that the fluid flow should change.