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Thread: Emergency Vehicle Traffic Preemption Systems

  1. #1
    Flashaholic*
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    Default Emergency Vehicle Traffic Preemption Systems

    First off, I don't know if this is the correct sub-forum for this. Moderators, I apologize in advance and please move it to the correct sub-forum, if necessary. Okay where is the best place to get up to speed on traffic preemption systems? For example, the specific frequencies used, pulse width, etc. I am finding quite a bit, but still looking for more.




    https://en.wikipedia.org/wiki/Traffic_signal_preemption

    https://ops.fhwa.dot.gov/publication...4/chapter9.htm

  2. #2

    Default Re: Emergency Vehicle Traffic Preemption Systems

    Planning on a DIY build project...?

  3. #3
    Flashaholic*
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    Default Emergency Vehicle Traffic Preemption Systems

    Quote Originally Posted by -Virgil- View Post
    Planning on a DIY build project...?
    Not hardly. My wife sent me a text this morning and she had the semaphores change due to an Opticom. She didn't see any emergency vehicles, but it could have been an unmarked vehicle.

    I found the high priority, low priority, and "audit" rates. I didn't even realize that there is an audit!

  4. #4

    Default Re: Emergency Vehicle Traffic Preemption Systems

    It can be a real rabbit hole deal, chasing after all the scarcely-documented features and modes on stuff like this. They understandably try to keep it out of the public eye. (No, I am not holding out on you; at this point you know more about it than I do.)

  5. #5
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    Default Emergency Vehicle Traffic Preemption Systems

    A good friend of mine formerly did emergency vehicle equipment installations. He knew about the high priority and low priority, but the "audit" rate was new to him.

    I definitely learned some things from this, too. I simply thought that they were designed for emergency vehicles, so when I read that they were originally designed for mass transit, it was something of an "a ha" moment, so to speak.

  6. #6
    Moderator Alaric Darconville's Avatar
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    Default Re: Emergency Vehicle Traffic Preemption Systems

    Quote Originally Posted by JAS View Post
    A good friend of mine formerly did emergency vehicle equipment installations. He knew about the high priority and low priority, but the "audit" rate was new to him.
    The audit rate may be useful to find the most common routes of emergency vehicles, or for an individual vehicle to add timestamp information to intersection crossings while following another vehicle, or any other number of things where you want to log that you went through the intersection but didn't preŽmpt the signal.

    I'd recommend that each preŽmption device also send a serial number so it's easier to tell who is using it. Of course, there may be someone trying to make their own device, but instead of rejecting them, logging the non-serialized preŽmption and activating a camera (for example, the red light camera) may help track down who is doing this unlawfully. Rejecting non-serialized/unknown serial units could cause more of a problem than it solves.

  7. #7
    Flashaholic ak645's Avatar
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    Default Re: Emergency Vehicle Traffic Preemption Systems

    Here in Broward county we use gps for mobile systems and hardwired for firehouse/railroad.Even though the vast majority of our signals are equipped for preempt only a few fire departments have trucks fitted with transceivers.PD and mass transit are not.Emergency vehicles approaching an intersection are not always in the lane for which they wish to proceed.For example sometimes a fire truck will be approaching in the right turn lane because it's clear then make a left at the intersection.So sometime the preempt doesn't work as intended.

    As for specific frequencies I highly doubt that information would be online.

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