Now this has been a few years back so my memory isn’t perfect. Don’t ask for a cite cause I can’t give one. Anyway, imagine a very large public housing development where the main entrance/exit is controlled by a red light. Imagine a police sergeant who has a device that controls said red light. Imagine him keeping the light red while he calls in license plate number after license plate number, arresting those drivers who have warrants out for unpaid traffic violations. Imagine said sergeant creating huge traffic jams and when someone finally figured out what was happening stating that he didn’t care about the traffic jams, he was enforcing the law. When interviewed by the newspaper reporter who broke the story, the sergeant described what he was doing and was quoted as saying “If the plate is clean, the light goes green.” Happened in Tampa a few years back.
yabob’s link in post#3 is real informative. It’s also about 6 years old. So the things it’s talking about happening soon probably happened a couple years ago.
The device used by emergency vehicles to change the traffic lights is called the Opticom.
The link has pictures of the receiver you’ll see on traffic lights. The Opticom’s we have on our ambulances are about a 3 inch square box mounted just in front of the light bar. The newest ones work by infrared. All of ours are coded, meaning there’s a specific pattern to the flashes that triggers a light change.
St. Urho
Paramedic
Or this.
The linked newspaper article details two fire trucks, en route to an emergency, approaching the same intersection at 90 degrees to each other. Though the article claims one of the trucks ran a red light to cause the accident, I’ve always wondered whether the at-fault truck initially had a green light, and the second truck Opticommed the light to give it the green instead. I’ve never heard whether this particular Opticom system had safeguards to lock out subsequent attempts to change the light and would love to know the full story. Or whether the first truck had a normal green and got the light switched on it with too little time to stop for the intersection.
(The end result was that the red-light-running fire truck t-boned the other fire truck, sending the entire mess to roll over the hapless bicyclist mentioned in the article. Unfortunately, she died. The emergency necessitating the fire trucks’ mad dash was another set of city workers using smoke to test sewer line integrity. Someone saw the smoke billowing from the pipes, called 911, 911 didn’t realize/get the word there was a test, and you know the rest. Just a sad story all around.)
Many many years ago, before they switched to infared systems, you could switch the light by hitting your high beams on and off in quick succession. I never learned the trick myself, but my ex always made *very *good travel times.
No he didn’t. Unless he can somehow flash his brights between 600 and 900 times a minute.
From my earlier link
St Urho, you might note that WhyNot said “many years ago”. Almost certainly before Opticom’s system existed. Early systems used uncoded visible strobes that flashed at a much slower rate that Opticom’s. So it was possible to flash your brights fast enough to trigger them. Or you could just mount a strobe on your car to do it. Doing either was illegal, of course.
The flashing your lights trick can supposedly work if you pull up to an intersection with an optical car sensor that isn’t detecting you due to poor visibility or because you didn’t pull up far enough. I think a lot of the people who swear up and down that it works may have got in a situation like this-- you sit and sit at a light, which doesn’t change because it doesn’t know you’re there, but it switches almost instantly after flashing your lights.
Most of the traffic signals in Los Angeles are connected to a central control room which can re-program the red/green sequence at will – mostly to control rush hour traffic, but presumably it can also be used for catastrophic emergencies or presidential motorcades. (Source: an episode of History’s Modern Marvels, IIRC.)
Opticom has been around for 35 years. Coded systems are newer, but the flash rate has always ben similar AFAIK.