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Energy Conservation Design Flaws in Traffic Signals

Discussion in 'Gen 2 Prius Main Forum' started by NoMoShocks, Jul 11, 2007.

  1. NoMoShocks

    NoMoShocks Electrical Engineer

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    I have made these observations about traffic signals that seem like design flaws from an energy conservation perspective.

    1. Two Lane Onramp Metering Lights - When in line for a pair of metering lights on a two lane onramp, I like to match my speed to the average speed of the line so I neither brake nor accekerate. When the last car ahead of me gets the green light, continuing to creap at the same speed would put me at the light just as it turned green, and I could accelerate to freeway speed from that roll, rather than a dead stop. But there is only one pavement sensor right at the limit line, so if you are not already there when it is time, the light in the other lane lets a second car go ahead of you because it thinks if no one sprints up to the line, the lane must be empty. I guess I have no choice but to zip into that position to avoid angering the drivers behind me.

    Standard Intersection with timing adjusted by pavement sensors - Similar situation, if you don't race up to the red light, you risk loosing your turn in the cycle and having to wait for the next one. Same think if you are not riding the bumper of the car in front of you, there is a good chance it will change to yellow.

    I wish traffic engineers would work to devise a way that would encourage hyermiling style of driving, which is safer too.
     
    #1 NoMoShocks, Jul 11, 2007
  2. alexstarfire

    alexstarfire New Member

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    IDK, but I noticed that long ago, the second part at least. We don't have on-ramp lights around here, only lights to turn onto the actual ramp from the intersection. Around here though it can be very odd because it's not always the same type of timing. It varies, though I can't say if it's always because of the time of day or not, between just straight up timed and motion sensored timed. The motion sensored time is when you have to be at the red light to get it to change, or to stay green a bit longer. The regular timed is when it doesn't matter about the car because the light will change no matter what.

    I personally hate all the lights around here cause they aren't even remotely timed. I do the same run basically twice daily and I can stop at one light and hit another one down the line, and then the next day (same time) hit the same light but hit a different light down the line. It very frustrating because there is no way to time for a light that changes timing.
     
    #2 alexstarfire, Jul 12, 2007
  3. NoMoShocks

    NoMoShocks Electrical Engineer

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    I didn't describe my second situation correctly. I meant to say regular intersection lights with timing adjusted by sensors in the pavement. If I don't rush up to the green lights full speed ahead, then I run a risk of the guy coming down the side street taking my green away. I don't actually do this. I am just saying that it becomes frustrating if I am slowing down for a red light to time it so I can get the green without stopping, and then as I get close it turns green, but then imediately turns yellow again becuase someone has raced up to a sensor on the side street.
     
    #3 NoMoShocks, Jul 12, 2007
  4. Sufferin' Prius Envy

    Sufferin' Prius Envy Platinum Member

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    The major flaw with a driver trying to maintain speed and reach the intersection at the time the light turns green is the increased chance of collisions with cross traffic drivers trying to beat the red light [like we never see that happen ;) ]. Serious accidents and fatalities would skyrocket if lights were timed that way. <_<

    At least here in California, it is the responsibility of the drivers with the new green light to make sure the intersection is clear before proceeding.

    Of course, this does not hold true for Onramp Metering Lights. In that case, the saved momentum would, in most cases, make for safer merging.
     
    #4 Sufferin' Prius Envy, Jul 12, 2007
  5. captnslur

    captnslur Junior Member

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    Another "flaw" in highway design and layout is the placement of speed limit changes. Here in Mankato (southern Minnesota) on a major highway there are speed change regulations which encourage poor fuel use.

    One is an speed change from 50 mph to 65 mph going up a moderate hill. To comply with that law one has to accelerate up the hill which forces hundreds of motorists every day to consume extra fuel. Most drivers, of course, begin accelerating far before the speed change. The speed actually changes only at the sign rather than, as most drivers figure, where one can see the sign. The most fuel efficient placement of the speed limit change to the down side of the hill and let gravity assist in the speed change.

    Yet another poorly positioned speed change here is a reduction in speed from 65 mph to 50 mph going down that same hill in the other direction. The most fuel efficient place for that change would again be on the up side of the hill a half mile before the present change place, again using gravity to assist in the speed change.

    :huh:
     
    #5 captnslur, Jul 12, 2007
  6. NoMoShocks

    NoMoShocks Electrical Engineer

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    <div class='quotetop'>QUOTE(Sufferin' Prius Envy @ Jul 12 2007, 03:02 AM) [snapback]477407[/snapback]</div>
    I think I understand what you are saying. People should not try to time the light so that it turns green just as they hit the intersection and they are still going 15 MPH, and would screach to a stop it it didn't change when they expect.

    But what I am saying, is that I would like to time the light so that if it changes to green when I am say 350 feet back, I can cautiously roll through it after carefully checking both ways. As it is, if you are coasting up to a light and it changes green when you are 350 feet back going 20 MPH, chances are it will turn yellow again before I get there.

    I cannot tell you how many times I have saved my self by hesitating when I light first turns green, and letting the last car go through after their orange light has changed ot a definative bright red. I have seen busses and large delivery trucks speed through on their red. One time, some friends were riding with me when this happened, and they told me, "Thanks for paying attention, I was just about to tell you it isn't going to get any greener."
     
    #6 NoMoShocks, Jul 13, 2007
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