Can L Reduce Freeway Traffic Slowdowns?
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Thread: Can L Reduce Freeway Traffic Slowdowns?

  1. #1
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    Default Can L Reduce Freeway Traffic Slowdowns?

    A recent article in MIT's Technology Review magazine finds that spontaneous traffic jams - slowdowns in heavy traffic that happen without an obvious obstacle - could be reduced if vehicles maintained equal distance between a slowing car ahead and the one right behind.

    This would prevent what normally happens when one car brakes sharply: the slowdown propagates back with increasing amplitude.

    The researcher hopes to avoid this through future widespread use of adaptive cruise control and front and rear facing cameras.

    But it's pretty close to the way I drive my Volt now on freeways. It's always in L, so as soon as I see the car ahead slow down I back off the accelerator, checking the rear view mirror to calibrate how rapidly it's safe to slow down. This absorbs much of the braking car's speed change, reducing the propagation of the slowdown.

    Yet another way that Volts make the world better.

  2. #2
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    I don't think driving in L is essential to the solution and in fact might make it worse for those behind you. The problem is basically from drivers not maintaining a constant speed and reasonable distance between cars. People slow down because of tunnels, bridges, jersey barriers, inattention. Others cut people off and weave in and out of traffic like it's a race course, etc.

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    Good catch TW. I've noticed this very same phenomenon and wondered the same thing. Beyond the "stopping" half of the equation, I think the smooth finely controlled starts of an EV also contributes here - smooth up, smooth down. There is always a ripple effect to a degree I suppose (i.e. time it takes each person to react, etc.) but the whole process would seem to be a smoother curve with EVs.
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  6. #4
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    Quote Originally Posted by cab View Post
    Good catch TW. I've noticed this very same phenomenon and wondered the same thing. Beyond the "stopping" half of the equation, I think the smooth finely controlled starts of an EV also contributes here - smooth up, smooth down. There is always a ripple effect to a degree I suppose (i.e. time it takes each person to react, etc.) but the whole process would seem to be a smoother curve with EVs.
    We call that "the accordion effect". An EV's instant torque and aggressive regenerative breaking would definitely help.

    As for me personally, driving in L on the freeway or in the city definitely helps keep me from riding the a$$ of the guy in front of me and makes me a little more patient in heavy traffic....
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  7. #5
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    Quote Originally Posted by Toolworker View Post
    A recent article in MIT's Technology Review magazine finds that spontaneous traffic jams - slowdowns in heavy traffic that happen without an obvious obstacle - could be reduced if vehicles maintained equal distance between a slowing car ahead and the one right behind.

    This would prevent what normally happens when one car brakes sharply: the slowdown propagates back with increasing amplitude.

    The researcher hopes to avoid this through future widespread use of adaptive cruise control and front and rear facing cameras.

    But it's pretty close to the way I drive my Volt now on freeways. It's always in L, so as soon as I see the car ahead slow down I back off the accelerator, checking the rear view mirror to calibrate how rapidly it's safe to slow down. This absorbs much of the braking car's speed change, reducing the propagation of the slowdown.

    Yet another way that Volts make the world better.
    +10! This has been my theory for decades.
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    Different people react differenly to the same traffic scenario. I think if you remove the human from the control (well maybe not completely) and if the cars are connected, things would move along smoothly.

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    Quote Originally Posted by 1ev View Post
    Different people react differenly to the same traffic scenario. I think if you remove the human from the control (well maybe not completely) and if the cars are connected, things would move along smoothly.
    Maybe. Or maybe the human would be dragged helplessly into a crash they could see coming but couldn't do anything about, because the computers fouled up somehow. In theory and with all the hardware working correctly, it will be a better system.

    This kind of problem is all about reaction time. Most people on busy freeways these days follow too closely for their reaction time, so by the time they register that the car in front of them is slowing down, they've already gotten into a dangerous situation where they have to slow down faster to prevent a collision - and then the guy behind them who's also inside his reaction time has to slam on the brakes.

    There are only two solutions for this without slowing down: Either the distance between cars has to increase so you have time to react appropriately, or your reaction time has to improve.

    The first seems unlikely - we are an ever more insane impatient society, and there are enough idiots that will jump in to that necessary reaction distance if you leave it open.

    The second is biologically improbable - but electronics have remarkably fast reactions, if somewhat poor judgement sometimes. So automated cars could potentially help the situation. My suggestion for how to do that is an improved HOV lane: Put an automated express lane on the inside of heavily travelled routes, and only allow cars equipped to negotiate into it. In theory, they should be able to maintain a much higher traffic volume in the same lane space, and keep everyone rolling.

    For the OP's discussion, I don't see that L makes a difference in and of itself. The difference is in your decision to slow down as soon as you see the backup, which does indeed help with the congestion. I suppose L may aid somewhat if your habit is to take your foot off of the gas immediately and wait to see if you need the brake pedal - because it is slowing your car more than you otherwise would.
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  10. #8
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    I don't see what 'L' specifically has to do with it...

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    Quote Originally Posted by saghost View Post
    For the OP's discussion, I don't see that L makes a difference in and of itself. The difference is in your decision to slow down as soon as you see the backup, which does indeed help with the congestion.
    That's basically correct. But I believe that people with that mindset will find L is the best match for their driving style.

    That style is what I consider an EV way of driving, which is to go into coast/regenerate at the moment you realize you need to slow down.

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  13. #10
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    OK, I'll say it.

    There'll be much less accordion effect if the people can see brake lights as you slow.
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