5 ms·

I think cars should “tug” on each other (communicating to eachother over RF somehow) and also act as a cushion (braking). When an intersection light turns gree

I think cars should “tug” on each other (communicating to eachother over RF somehow) and also act as a cushion (braking). When an intersection light turns green - all cars should begin rolling together. Waiting for cars in front of you in succession is burning time.

VierScar 8y ago
Waiting for cars in front of you is for safety and would be the case even with fully automated nationally adopted self driving electric cars. When you're stopped you don't need a buffer so much for when things go wrong, but at higher speeds you need a bigger buffer, and having space helps avoid mass catastrophes when some freak storm knocks a tree branch onto the road or a car malfunctions or mechanical failure/wear and tear.
adrianmonk 8y ago
I've pondered a similar question: is pulling up right behind the car in front of you the optimal behavior for a red light? What if you could get everyone to leave a large gap (on the order of several car lengths)? Could you increase the number of cars that make it through a light while it's green? Or would it not matter? Human nature is to pull as far forward as you can, within certain limits at least. But is that actually optimal? If not, with self-driving cars or some other technological assistance, maybe we could increase the efficiency of intersections that use signals.
- WrtCdEvrydy 8y ago
  Self Driving Cars have two advantages: Data Transfer allows for instant start/stop so the car can actually stop before the light turns, allowing the cars on the other side to go quicker and go immediately. In the future, we may not even see self driving cars stopping at red lights (think of all intersections as four way roads)
- cgriswald 8y ago
  Sure, you can probably optimize for that, but understand that you’re preventing people from turning on red or getting into the left turn lane in time for the signal to appear this cycle and you’re also trapping people going straight on the other side of the previous intersection. I suspect it might be good for getting through that intersection faster, but in general I think it’s probably best for all traffic if stopped traffic takes up as little room as possible.
  - adrianmonk 8y ago
    Yeah, if the effect even matters, it wouldn't work well for short blocks. Even for long blocks, you'd want to figure out that the light will be green for X seconds, which allows Y cars to get through, so only Y cars (and no more) would line up with the required spacing between them, and the ones behind that would pack in more tightly to save space. Then while the light is right, the next Y cars could get themselves into the correct configuration.
  - kosievdmerwe 8y ago
    Given that there's more distance to traverse if you leave gaps, it might turn out that it takes the same amount of time. I haven't done the maths, but it wouldn't surprise me if they're about the same.
- amenghra 8y ago
  https://youtu.be/HO2zVYB1TMc https://youtu.be/HO2zVYB1TMc is some fun research, simulating an intersection where autonomous vehicles self-synchronize their paths.
yason 8y ago
When an intersection light turns green - all cars should begin rolling together Will not work. The safe distance between cars is negligible in traffic lights but a lot more in moving traffic. At least two seconds is considered reasonable although in reality much lower distances are seen. The "rolling together" would only work if the queue to the traffic light would copy the distance needed by moving cars. That is, the cars would be spaced 10-40 meters apart while waiting for green. Only then all cars could floor it and accelerate together without having to wait for the first units to run away first.
- executesorder66 8y ago
  I disagree. Let's say we are in an area with a 60km/h speed limit. Going 60 km/h you do need a wide gape between cars. But once you stop at a traffic light you should leave enough of a gap to see where the types car in front of you touch the road. That way you are not too close to get around the car if it gets stuck. When the light goes green, lets say the first car accelerates slowly and only reaches 30km/h by the time they cross the traffic light. If every car behind waited until there was 1.5 car length gap, then only half the cars would get through compared to if they all accelerated at the same speed at the same time, maintaining a smaller gap until they cross the traffic light. You only need the large gap once you've accelerated up to a much higher speed.
  - Drew_ 8y ago
    Any extra space you leave between you and the car in front of you is artificial traffic you're creating. That's space that could be used by more cars. Ideally, at a traffic stop every car would sit literally bumper-to-bumper to maximize throughput but that's obviously not reasonable. You can see clearly from the simulation that having the opportunity to move around an obstruction doesn't stop the ensuing slow down from occurring because you have to slow down and reduce the bandwidth of the road to move around the obstruction.
  - yason 8y ago
    You only need the large gap once you've accelerated up to a much higher speed. Going from small gap while standing in lights to large gap at a higher speed cannot be reached in unison. The later cars must inevitably accelerate slower or the first cars must accelerate faster in order for the larger gaps to appear. So even if all cars did in fact start rolling at the exact same time when the light turns green the acceleration of any tailing car is bounded by some safety margin as a function of speed.
mariefred 8y ago
Scania, and probably others, are working on platooning trucks. From what I know it is not trivial, for example most of communication methods we have have too long round trip delays and are not 100% reliable so a backup is needed maybe in the form of autonomous breaking system. https://www.scania.com/group/en/platooning-automated-driving-for-fuel-savings/ https://www.scania.com/group/en/platooning-automated-driving... https://platooningensemble.eu/news/using-its-g5-for-efficient-truck-platooning5c1a203e7a226 https://platooningensemble.eu/news/using-its-g5-for-efficien...
- z3t4 8y ago
  Could probably be solved with a direct connection, like antennas touching each other.
  - nightfly 8y ago
    Just replace cars with giant ants.
  - mariefred 8y ago
    touching ? those are fast moving vehicles that can be a few meters to many meters from each other, and possibly have some other vehicle in between
    - z3t4 8y ago
      If they are too far away they will not get the lower fuel consumption (due to air resitence), and they wouldn't need micro-second latency response times. So they could use the current radio technology if the antennas are too far away to touch. There could also be sensors in the antennas to feel if the vehicles are out of sync. And alert the driver when they are disconnected.
deleted 8y ago
[deleted]
executesorder66 8y ago
> When an intersection light turns green - all cars should begin rolling together. Agreed. I've always suspected/known this. Just play with the acceleration settings in the simulation for proof. I hate when the light goes green and people wait for a gap before driving. Just go, you are barely going 20km/h at this stage. If everyone accelerated quickly until they were on the other side of the traffic light, you could get double the amount of cars through. No need to break the speed limit.
- michaelt 8y ago
  I stopped doing that after I bumped into the guy ahead, who didn't notice the light had gone green.
  - executesorder66 8y ago
    You didn't do that then. If you had been accelerating at the same speed as the person in front of you, and started at the exact same time as them, you would never have bumped into them. If they didn't move, then obviously it's retarded to jsut start driving. My point is when the car in front of you _does_ start moving, you need to move too, at the same speed/acceleration. Not wait.

VierScar 8y ago

Waiting for cars in front of you is for safety and would be the case even with fully automated nationally adopted self driving electric cars. When you're stopped you don't need a buffer so much for when things go wrong, but at higher speeds you need a bigger buffer, and having space helps avoid mass catastrophes when some freak storm knocks a tree branch onto the road or a car malfunctions or mechanical failure/wear and tear.

adrianmonk 8y ago

I've pondered a similar question: is pulling up right behind the car in front of you the optimal behavior for a red light? What if you could get everyone to leave a large gap (on the order of several car lengths)? Could you increase the number of cars that make it through a light while it's green? Or would it not matter? Human nature is to pull as far forward as you can, within certain limits at least. But is that actually optimal? If not, with self-driving cars or some other technological assistance, maybe we could increase the efficiency of intersections that use signals.

WrtCdEvrydy 8y ago
Self Driving Cars have two advantages: Data Transfer allows for instant start/stop so the car can actually stop before the light turns, allowing the cars on the other side to go quicker and go immediately. In the future, we may not even see self driving cars stopping at red lights (think of all intersections as four way roads)
cgriswald 8y ago
Sure, you can probably optimize for that, but understand that you’re preventing people from turning on red or getting into the left turn lane in time for the signal to appear this cycle and you’re also trapping people going straight on the other side of the previous intersection. I suspect it might be good for getting through that intersection faster, but in general I think it’s probably best for all traffic if stopped traffic takes up as little room as possible.
- adrianmonk 8y ago
  Yeah, if the effect even matters, it wouldn't work well for short blocks. Even for long blocks, you'd want to figure out that the light will be green for X seconds, which allows Y cars to get through, so only Y cars (and no more) would line up with the required spacing between them, and the ones behind that would pack in more tightly to save space. Then while the light is right, the next Y cars could get themselves into the correct configuration.
- kosievdmerwe 8y ago
  Given that there's more distance to traverse if you leave gaps, it might turn out that it takes the same amount of time. I haven't done the maths, but it wouldn't surprise me if they're about the same.
amenghra 8y ago
https://youtu.be/HO2zVYB1TMc https://youtu.be/HO2zVYB1TMc is some fun research, simulating an intersection where autonomous vehicles self-synchronize their paths.

yason 8y ago

When an intersection light turns green - all cars should begin rolling together Will not work. The safe distance between cars is negligible in traffic lights but a lot more in moving traffic. At least two seconds is considered reasonable although in reality much lower distances are seen. The "rolling together" would only work if the queue to the traffic light would copy the distance needed by moving cars. That is, the cars would be spaced 10-40 meters apart while waiting for green. Only then all cars could floor it and accelerate together without having to wait for the first units to run away first.

executesorder66 8y ago
I disagree. Let's say we are in an area with a 60km/h speed limit. Going 60 km/h you do need a wide gape between cars. But once you stop at a traffic light you should leave enough of a gap to see where the types car in front of you touch the road. That way you are not too close to get around the car if it gets stuck. When the light goes green, lets say the first car accelerates slowly and only reaches 30km/h by the time they cross the traffic light. If every car behind waited until there was 1.5 car length gap, then only half the cars would get through compared to if they all accelerated at the same speed at the same time, maintaining a smaller gap until they cross the traffic light. You only need the large gap once you've accelerated up to a much higher speed.
- Drew_ 8y ago
  Any extra space you leave between you and the car in front of you is artificial traffic you're creating. That's space that could be used by more cars. Ideally, at a traffic stop every car would sit literally bumper-to-bumper to maximize throughput but that's obviously not reasonable. You can see clearly from the simulation that having the opportunity to move around an obstruction doesn't stop the ensuing slow down from occurring because you have to slow down and reduce the bandwidth of the road to move around the obstruction.
- yason 8y ago
  You only need the large gap once you've accelerated up to a much higher speed. Going from small gap while standing in lights to large gap at a higher speed cannot be reached in unison. The later cars must inevitably accelerate slower or the first cars must accelerate faster in order for the larger gaps to appear. So even if all cars did in fact start rolling at the exact same time when the light turns green the acceleration of any tailing car is bounded by some safety margin as a function of speed.

mariefred 8y ago

Scania, and probably others, are working on platooning trucks. From what I know it is not trivial, for example most of communication methods we have have too long round trip delays and are not 100% reliable so a backup is needed maybe in the form of autonomous breaking system. https://www.scania.com/group/en/platooning-automated-driving-for-fuel-savings/ https://www.scania.com/group/en/platooning-automated-driving... https://platooningensemble.eu/news/using-its-g5-for-efficient-truck-platooning5c1a203e7a226 https://platooningensemble.eu/news/using-its-g5-for-efficien...

z3t4 8y ago
Could probably be solved with a direct connection, like antennas touching each other.
- nightfly 8y ago
  Just replace cars with giant ants.
- mariefred 8y ago
  touching ? those are fast moving vehicles that can be a few meters to many meters from each other, and possibly have some other vehicle in between
  - z3t4 8y ago
    If they are too far away they will not get the lower fuel consumption (due to air resitence), and they wouldn't need micro-second latency response times. So they could use the current radio technology if the antennas are too far away to touch. There could also be sensors in the antennas to feel if the vehicles are out of sync. And alert the driver when they are disconnected.

deleted 8y ago

[deleted]

executesorder66 8y ago

> When an intersection light turns green - all cars should begin rolling together. Agreed. I've always suspected/known this. Just play with the acceleration settings in the simulation for proof. I hate when the light goes green and people wait for a gap before driving. Just go, you are barely going 20km/h at this stage. If everyone accelerated quickly until they were on the other side of the traffic light, you could get double the amount of cars through. No need to break the speed limit.

michaelt 8y ago
I stopped doing that after I bumped into the guy ahead, who didn't notice the light had gone green.
- executesorder66 8y ago
  You didn't do that then. If you had been accelerating at the same speed as the person in front of you, and started at the exact same time as them, you would never have bumped into them. If they didn't move, then obviously it's retarded to jsut start driving. My point is when the car in front of you _does_ start moving, you need to move too, at the same speed/acceleration. Not wait.