Does flashing your headlights at traffic lights really change them?

Question

if traffic lights are light sensitive then why dont they go go heywire during daylight hours or during a lightning storm. I always thought they worked from microwaves which detected a moving solid object.

Answer 1

No, flashing your headlights has absolutely no effect. There are several methods that cause the traffic signal to change (flashing your light is not among them).

1. The most commonly used method is an inductive loop of wire buried in the lane of traffic behind the "stop line". Basically, it's a metal detector. When a car pulls up on this loop it causes a change in inductance which causes a relay to close and signalling the timer that there is a vehicle on that approach that will need a green light.

2. Quickly replacing inductive loops are video cameras mounted on the signal poles. These cameras are pointed toward each approach to the intersection and programmed with zones in each field of view. When a vehicle enters this zone the camera signals the timer that a vehicle is awaiting a green light.

3. Microwave detectors are useful but not as adaptable or versatile in their use. When a vehicle enters the area covered by the microwave beam it acts in much the same manner as #1 and #2.

4. Magnetometers are rapidly falling out of use. They were a large coil of wire (called a torpedo) inserted in a conduit under the lane of traffic. When a car pulled up to the intersection and was over the "torpedo" it caused a change in the magnetic field and (as with the others) signalled the timer. Magnetometers were never that reliable as they had to be "retuned" much too often and didn't detect all cars awaiting a green light.

5. Pressure switches are all but discontinued. These were a treadle placed in a large metal box at or near the "stop line" when a car pulled across the treadle it signaled the timer there was a car waiting for a green light. The switches often broke, and the treadles only covered an area about 2' x 8' in a lane of traffic. While they did work, they did not work very well.

I have 25 years experience with traffic signals.

Hope I helped answer your question.

Answer 2

Flashing Lights At Traffic Lights

Answer 3

This is an emergency services trick. If you do it early enough, the bright lights can trigger the system before it would detect the rest of your vehicle. It only works on a particular type of sequencer, though - you have to know which ones. This is why you see a lot of people flashing away with no effect. Pedestrian crossing ones are the best example of this. It will not work here. It also will not work if the sequence has already been affected by the arrival of other vehicles at other lights in the set. Basically, if you're just randomly flashing traffic lights, you've got maybe a one in ten chance of it having any affect. If you know the system, it's about one in four.

Answer 4

No. Traffic lights don't work like that.
Have you ever wondered why there appear to be random 'lines' of bitumen on the road surface before a traffic light? Those are the traffic sensors. They work a bit like a metal detector - they're buried in the road, and can tell whenever an object with a high metal content is sitting in the road (ie. a motor vehicle). This tells the lights where traffic is waiting, and where the road is clear.

Answer 5

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How do you know they are radar units and not just cheaper and simpler optical sensors? When have the government ever spent money on the most expensive and unreliable method of doing anything? Oh hang on they do it every time don't they! Train signalling, channel tunnel, motorways, airport runways and of course their salaries point taken. But I did think that permanent signals used induction loops under the road and temp ones used optical sensors to reduce waiting times at night and programmable timers during the day. If I am wrong then OK but why does it "work" quicker if you flash the sensor directly than when you don't? Have you ever tried sneaking up on one without your lights on to prove it? The USA might have radar units but have you checked to find out if ours do? As a minor point radio and light are the same thing just different wavelengths so radar does have something to do with light

Answer 6

It only works with lights on side roads that have sensors on top.

Flashing your headlights fools the sensor into believing that numerous vehicles are waiting at the lights and so they change.

you don't see them on main roads as the volume of traffic passing would be picked up by the sensor and the lights would never change.

Not a good idea when statistics show that you already spend at least 5yrs of your life sitting at traffic lights!!!

Answer 7

In the Netherlands, early in the morning when I pass the traffic lights and they are red, I flash my headlights and they always turn green, I never have an exception, even when at the other side cars are waiting. So, my answer would be yes: definitely

Answer 8

No. Traffic lights in London and other UK cities are on computer-programmed time switches, which can be overridden from HQ in case of emergency.

Flashing your lights is like pressing the lift button twice. It may express your impatience but it won't speed things up.

Answer 9

Some work on sensors, but I don't think flashing your lights at the majority of lights would make a difference. Plus, it could be quite dangerous!

Answer 10

Nope, that makes no difference. Traffic lights are set on timers, or motion sensors/cameras that detect the presence of cars. Anything else is just a myth.