Talk:Traffic signal preemption

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)

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)


 * 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)

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.
 * From original poster:

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 undefined 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)


 * Original research isn't allowed on Wikipedia anyway. Find a source confirming your findings & modify the article with citations.  You are right though that is is perhaps not an urban legend.  It would better be described as a common misconception arising from coincidence. Djcable1 (talk) 02:10, 20 December 2014 (UTC)

I'm just a random passer-by, but I wanted to add that most dynamic traffic signals that I've seen are triggered by a loop of wire embedded in the tarmac that detects electrical activity (and not weight). If you're not directly on top of the loop (which you can clearly see), or if the sensor is defective, it won't trigger it, but flashing your headlights can increase the electrical activity variance enough that it trips the sensor. I'm not suggesting that my so-called "original research" should be included in the article, but put this here as it may answer the OP's situation. 70.75.132.111 (talk) 14:56, 16 June 2016 (UTC)

Commercial Pitch
I've toned down the following obvious commercial pitch: 'However the Eliminator“TM” by Collision Control Communications, Inc. does not have these limitations, and also gives advance warnings of collisions with similarly equipped emergency vehicles; find out more here:Eliminator for Collision Avoidance and Traffic Signal Preemption.' However, the article still seems to contain bias toward the Eliminator product. Wikipedia articles are supposed to be impartial, and the article should be further rewritten so that it doesn't come across quite so circumspect. —Preceding unsigned comment added by 24.114.236.17 (talk) 21:06, 14 March 2009 (UTC)

Commercial Pitch, Part 2 (edit war)
Anonymous user at 71.127.121.231, do not restore the heavily biased section regarding the 'Eliminator' product again without first reading and understanding Wikipedia's policy on Neutrality. Discussion of what the Eliminator does, how it differs from other products, etc, is not strictly prohibited, but must be presented without the commercially-slanted description that was just removed (again). Wikipedia is not an advertising or promotional platform. Continued ignorance/defiance of Wikipedia policy can and will lead to you being blocked from editing. Thanks. Fjbfour (talk) 18:14, 11 June 2009 (UTC)

Anonymous User 71.127.121.231
Please limit the ability of edits that can be made by this user, 71.127.121.231. He has removed links which were deemed informative and non-promotional, to replace with a link simply bringing whoever clicks it collisioncontrol.net, the home page of 'The Eliminator' product. There is nothing on that page that could be used to answer the question 'What Is Traffic Signal Preemption', which the link had been disguised as.

Global Positioning System section overly criticle and contains outdated information
There is no requirement for a "central application to activate the desired traffic lights". The EMTRAC system (which I'm affiliated with) works autonomously via hardware in the vehicles which communicate via radio to hardware in the traffic cabinets. A central application is not required, but can be used for real time monitoring and logging.

Urban GPS environments are difficult, but it is unneeded to paint the situation so negatively. The concept of GPS being plagued with single point of failure problems seems excessive. In my experience atmospheric conditions and heavy cloud cover are very rarely an issue. Today's GPS modules are quire good.

Urban areas do have GPS difficulties from reflection. It might be interesting to mention the urban canyon effect in relation to this. All these poor GPS quality situations can be augmented with dead reckoning techniques; the combining of GPS data with sensors and mathematically intensive calculations to retain reasonable position accuracy. Some sensors might include wheel ticks, gyroscopes, and accelerometers. This type of augmented GPS system is commercially available and preforms well.

The gloom-n-doom representation of the future of GPS health is not recent nor realistic. The citation #5, 'GPS satellite system 'close to breakdown' and could fail by 2010', was published on 9th May 2009. the current GPS timeline shows that there has been 2 GPS satellites deployed since that pessimistic article was publish. I think governments and private companies have ongoing incentive to maintain a well working network of GPS satellites for quite some time, making such statements seem biased. — Preceding unsigned comment added by 76.11.241.96 (talk) 18:01, 7 November 2011 (UTC)


 * I edited parts of this section to correct some errors (triangulation vs trilateration), some inconsistencies (three vs four satellites required) but left much of the negativity as I don't have any experience with GPS in this use case. I did remove the doom and gloom about the health of the constellation. Cothrun (talk) 04:32, 21 August 2014 (UTC)

Preempt
the preempt link in this article links to a bridge article (the card game bridge). pretty sure that should be changed. — Preceding unsigned comment added by 76.19.102.88 (talk) 22:14, 12 January 2012 (UTC)

I was just going to make the same comment. Hgesser (talk) 19:53, 9 April 2012 (UTC)

External links modified
Hello fellow Wikipedians,

I have just added archive links to 1 one external link on Traffic signal preemption. Please take a moment to review my edit. If necessary, add after the link to keep me from modifying it. Alternatively, you can add to keep me off the page altogether. I made the following changes:
 * Added archive https://web.archive.org/20061003123315/http://www.i2i.org/main/article.php?article_id=1106 to http://www.i2i.org/main/article.php?article_id=1106

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Cheers.—cyberbot II  Talk to my owner :Online 16:05, 15 January 2016 (UTC)

Proposed merge with Bus priority
Content of this page is not worthy for its own page as it looks completely like OR. Merge content instead to a broader topic. « « «  SOME GADGET GEEK  » » » (talk) 14:43, 18 April 2017 (UTC)
 * Oppose; The article is not bus-specific. -User:DanTD (talk) 11:55, 5 August 2017 (UTC)
 * Oppose; This has nothing to do with buses. This is generally for emergency vehicles, not for buses. LionWaffles (talk) 01:43, 13 September 2017 (UTC)