Can a traffic signal's YELLOW interval be less than 3 seconds?

Friend got a ticket.
He claims the YELLOW was ONE second and he had no time to stop before RED.

Can a traffic signal system’s YELLOW interval even be set to less than 3 seconds?

Thank you.

Technically, yup.
Whether state statutes mandate a minimum time and what that might be is up to each individual state. If your friend wants to contest the ticket, he/she should do some research as well as do a video that “times” the duration of the light.

Yes, the signal timing is controlled by software that can be set to whatever intervals the programmer chooses. The typical yellow interval is 3-6 seconds, but it can be set for less.

Can it?

Should it?
Obviously, no

In NJ, in the wake of the installation of Red Light Cameras by several municipalities, it came to light that some of those towns had shortened the amber light interval to less than 3 seconds. IIRC, the state ordered that those traffic signals be re-set for a 3 second interval, and the folks who had gotten tickets at those particular intersections had to have their fines refunded to them.

Of course, this rectification did not happen spontaneously, and was the result of a class-action suit.

Even three seconds is not adequate. Should be 5 to 6 seconds.

Absolutely. In our town the newest traffic lights that are installed get a flashing yellow for about 8-10 seconds. The red lights on top are also in pairs. I like them. On the other side of town…the yellow lights last for about 3-4 seconds with a single red light.

Did they get a ticket from a red light camera?
If so, then the yellow light’s timing was probably changed to increase revenue from unsuspecting motorists.

Case in point. The yellow light time was reduced in order to ticket unsuspecting motorists:

There should be a Nationwide standard for length of yellow lights. Could be 3, could be 6, see yellow, slam on the brakes and risk getting rear ended just in case? Rather get a red light ticket than an accident, though around me it seems as long as it turns red you still have 3 seconds to run the light.

Did they get a ticket from a red light camera?
Police officer waiting for violators caught him. In court he claimed it was one second. They, and I, do not believe it. My recall is that they cannot even be set to less than 3 seconds.

They allow you to start coasting/braking when you know that you will not make the green signal.

In my wife’s hometown in China, they have count-down signals.
Example: GREEN numbers indicating GREEN phase in seconds appear: 40, 39, 38…3, 2, 1,
Then RED 30, 29, 28…3, 2, 1,

Here’s some interesting advice from the article I posted above:


10 News cannot provide legal advice, but you may have grounds to appeal an automated citation for a variety of reasons. If you believe you were ticketed because of a short yellow light, you may want to:

Go online to review your ticket and record the video with a cell phone or other recording device.
Going frame-by-frame, detemine if the yellow light failed to last as long as mandated by the TEM chart posted above. Also note how long the light was red before you entered the intersection.
You may be able to appeal if you can prove the yellow light was too short and you would have normally made it through a normal yellow light.
Even if the length of the yellow light meets the minimum, you may still be able to appeal if the yellow intervals are too short for drivers’ actual average approach speed. The national suggestions posted above indicate safe stopping speed should be considered when planning RLC placements and yellow light times.

I seem to recall there was a traffic light somewhere that had a shorter time interval than normal yellow apparently. Someone got a ticket and contested it in court using a video camera, proving that the yellow was of shorter duration than the state’s traffic code permits. The judge made a visit to the intersection and verified the timing himself, then dismissed the ticket and ordered red light violation tickets written at that intersection within the past year dismissed and any fines paid refunded.

“There should be a Nationwide standard for length of yellow lights”

Under the principle of separation of powers, things like traffic regulations are w/in the purview of each state. Hence, the differences in traffic laws from one state to another.

Here’s another interesting website on the subject:

Apparently short yellow lights are a common problem.

In case it hadn’t been mentioned, the length of a yellow light should coincide with the speed limit. One second for every ten miles an hour for example. So a yellow light should be longer in a 45 then a 25. I have been on 55 mph roads with lights. 5 seconds would be an absolutle minimum IMo there.

@dagosa, see the above link for the formula that traffic engineers use to calculate timing.

According to that formula, at 55 mph the yellow interval should be around 3.5 seconds, but the National Motorists Association is recommending 6 seconds at 55 mph, which sounds much more reasonable.

Correction: Oops, 55 mph is 80 ft/sec, in which case the formula gives a yellow interval of 5 seconds, not 3.5. That sounds better.

Thanks ! Your post wasn’t up when I typed mine out from memory. It certainly sounds reasonable. We know how time distance and speed are related so using speed to determine the time seems very apropo.

It does seem strange that yellow lights aren’t longer. There’s no reason I can think of to make them so short. Longer (within reason) is always going to make an intersection safer, I would expect.

Longer yellow lights mean that more people will try to get through the intersection before the light turns red, increasing the safety hazard. Around here, far too many people run “pink” lights now. Encouraging them to continue moving ahead after the light turns yellow is dangerous.

I guess there is some happy medium to be achieved.