Talk:Traffic signal preemption
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[edit] Merge with Opticom System and STROBECOM articles
The other two articles are stubs, and both are brand name products for this device. Neither is substantially different as to warrant its own page IMHO. In addition people visiting either page likely will have to visit the signal preemption page to understand what the device does. --MMX 04:04, 21 June 2006 (UTC)
It's been a while. Making a second call for comments on merging these three articles. --MMX 04:57, 13 July 2006 (UTC)
[edit] Is flashing your headlights really an urban legend?
The article states that flashing your brights to trigger a traffic light to turn green is an urban legend due to the requisite frequency, etc. I've personally flashed my brights on many occasions and successfully changed the light. I've only done it in the dark, and I've only tried in upstate NY and Wisconsin.
I've done this several dozen times and seen success each time. I could understand if I had only tried it once and it worked right when the light was about to change anyhow, but I'm talking about dozens of times. The odds of it just being coincidental that many times seems extremely unlikely.
I understand the argument for why it's not possible and the argument sounds great on paper. The problem is that I've done it in real life many many times with success every time. Perhaps this should not be listed as an urban legend.
- It sounds good on paper because it is true. Let me ask you this: How many times have you arrived at a red light and the light never changed to green? I suspect that unless you found a malfunctioning traffic light, the answer will be zero. Given that the vast majority (if not all) of the red lights eventually turn to green upon your approach or arrival, does the fact that you flashed your high beams mean that they caused the light to change? I suggest a controlled experiment: Spend an entire week approaching red lights and flash your high beams (both day and night) and count how many change for you, be sure to add up the seconds you sit still waiting for the light. Then spend the next week doing nothing, but adding those seconds. Please report your findings. Fjbfour 07:05, 21 April 2007 (UTC)
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- Further comments from me - remember that unless a signal is part of a synchronized sequence of signals, it will have sensing equipment to determine when a vehicle needs a green light, and unless there is active conflicting traffic it will change it just as you arrive or as soon after as possible. This would occur coincidentally and suspiciously soon after you flashed your high beams. On the other hand, traffic preemption devices have a very long range, and will trip green lights for many blocks in advance. If flashing your high beams was effective, it would cause green lights for up to or over a quarter mile directly ahead of you in the line of sight from your headlights. Fjbfour 16:53, 21 April 2007 (UTC)
- From original poster:
First, I realize that correlation does not imply causation. So yes, I know that it could be coincidental. To answer the first question, at a light that flashing my brights has worked (not all lights seem to work) I have NEVER had a failure. In other words, if I've ever succeeded at traffic light N then I have had a 100% success rate there.
Second, it cannot be due to approaching because I've had many occurrences of arriving, sitting at the light for a while, and then flashing my brights to make it change. I've done this at the same lights that I know from experience that flashing works so that it would be an experiment of sorts.
So, I know that it's not a completely controlled experiment and that there is certainly a moderate margin of experimental error, but nonetheless I've seen it work so many times (for both myself and others) that I find it very difficult to believe it to be coincidental. I understand the physics of the counter-argument. I know that a typical car headlight cannot flash a a frequency anywhere near that of an emergency vehicle, nor does it have anywhere near the same strength (or angle, for that matter). But, nonetheless, I've seen it work.
Come on out to Verona, Wisconsin (a place I know it works) and try for yourself. You'll be surprised.
- This may be an old thread but I wonder if those stoplights where you flashed your brights at have a Camera Control System. At the intersections where I come into this scenario and found out about this, they used cameras to detect cars and sometimes are stubborn at detecting cars sometimes a flashing light would make them change. I another case at the same camera controlled intersection I saw a police car waiting at the intersection preempt the light by turning on his pursuit lights, this could also explain why it did it too becasue of so called flashing lights. IMO this is a plausible scenario. Sawblade05 (talk to me | my wiki life) 10:34, 5 November 2007 (UTC)
- Generally, in emergency vehicles, all emergency lights have individual switches that are all sourced through a master switch. If you leave the individual switches on and the master off (normal configuration), you can then engage everything with just the single master switch, but the capability is still there to be selective in the odd situation that you only want certain things on. The most common traffic pre-emption application is to also wire the pre-emption emitter device through this master switch, one less thing to hunt down and turn on in an emergency. If a police car was in a moderate hurry and needed to pre-empt a light, flipping the master switch (activing all emergency lights along with the emitter) is a lot simpler than turning all of the warning devices off except the emitter, then turning on the master to to engage the emitter and pre-empt the light, followed by putting all the switches back - while being a bit of a rush. Fjbfour 14:34, 5 November 2007 (UTC)
