Why traffic lights don't flash in the wee hours.

September 5, 2005 7:10 AM

Traffic lights no longer flash in the wee hours. Why?

I don't know about your area, but in and around Cincinnati, the traffic lights used to flash red or yellow in the low-volume traffic hours of, say, midnight till 4AM. This is no longer the case. I work early in the morning and get so frustrated when I have to stop at a damn red light when there isn't a soul around for miles. Any explanations or can anyone comment on this observation?

posted by cincidog to travel & transportation (23 comments total)

Call Roy Jones at 352-3737. He is the city engineer in charge of traffic signal timing and interconnection. If he doesn't know, no one on Earth knows.
posted by pracowity at 7:30 AM on September 5, 2005

Local Municipalities choose their own times for setting flashing hours.

I suspect that they changed based on the amounts of drunks, accidents, or traffic volumne.
posted by filmgeek at 7:33 AM on September 5, 2005

and when you do call him, please post back here, because I'm interested.

What does it mean when they flash? Is it that they're not in use, and traffic should behave as if there's no light there?
posted by bonaldi at 7:36 AM on September 5, 2005

It tends to mean (at least in the UK and Spain) that you must be aware and, generally, give priority to the right, but you don't have to stop - ie: treat them as if they're not there and drive as you would to a normal same-priority junction. They flash rather than turn them off so you don't think they're broken...
posted by benzo8 at 7:38 AM on September 5, 2005

I always thought you would treat them like you would a stop sign when they're flashing.
posted by monkey!knife!fight! at 7:39 AM on September 5, 2005

Normally, the busier route will flash yellow, meaning proceed with caution, and the less busy throughfare will flash red, meaning stop, THEN proceed with caution, after yielding to the other traffic.
posted by cincidog at 7:42 AM on September 5, 2005

I failed to do the requisite Google search prior to my posting. Upon further research, requiring SECONDS of my valuable time, I found this link with the following quote from Houston:

A: Many other cities do exactly what you have suggested. On roads less traveled, lights are turned to flashing mode late at night, blinking yellow for the priority street and red for the cross street. I love this approach. It's no doubt annoying to sit at a red light in the middle of the night when nobody is around.

The city of Houston will not adopt such a policy, however, said Wes Johnson, public works spokesman. Johnson explained there are concerns with safety and maintenance.

"Drivers do not understand the meaning of flashing lights," he said. "Late-night drivers include persons who are more likely to be tired or inebriated. You tend to have more accidents at flashed signals."

Having bulbs flash also creates the need for more signal upkeep, he said.

Instead, the city is working to better time the lights and install detection cameras so cars are not held up at red lights.

Do I get to mark my own post as the best answer to my own question?
posted by cincidog at 7:48 AM on September 5, 2005

You know, it's ridiculous that all late-night drivers must be inconvenienced by the idiotic few who don't know the rules of the road or those who drive when tired or inebriated. Understanable, but still ridiculous. If you are a driver that doesn't know what a flashing red or flashing yellow light signifies, then you do not deserve the privilege of using the public streets.
posted by Rhomboid at 7:55 AM on September 5, 2005

cincidog writes "Normally, the busier route will flash yellow, meaning proceed with caution, and the less busy throughfare will flash red, meaning stop, THEN proceed with caution, after yielding to the other traffic."

Yeah - we only get flashing amber here in Europe - not the reds - so we always treat them as a "Give Way" ("Yield" in the US?) which means you don't have to stop.
posted by benzo8 at 7:57 AM on September 5, 2005

What does it mean when they flash? Is it that they're not in use, and traffic should behave as if there's no light there?

This is why they don't flash any more, cincidog. :)
posted by Hildago at 8:12 AM on September 5, 2005

If you are a driver that doesn't know what a flashing red or flashing yellow light signifies, then you do not deserve the privilege of using the public streets.

Given the number of drivers who don't know what a regular non-flashing yellow light means, I don't see what option they have. If they took away their driving privileges of people who didn't know what the signals meant, there would be so few drivers on the road they could just have flashing lights all the time.
posted by duck at 8:19 AM on September 5, 2005

It tends to mean (at least in the UK and Spain) that you must be aware and, generally, give priority to the right, but you don't have to stop - ie: treat them as if they're not there and drive as you would to a normal same-priority junction. They flash rather than turn them off so you don't think they're broken...

Perhaps in Spain, but not in the UK. Traffic lights don't flash in the UK other than on the very short flashing amber before going to green on certain pedestrian crossings.

Part-time traffic lights in the UK are always marked as such with a sign saying "Part-time lights" or similar.
posted by wackybrit at 8:28 AM on September 5, 2005

Around here (Ontario, Canada), flashing red means you treat it like a four-way stop sign. Flashing yellow means proceed with caution. (And when the lights are out altogether, e.g. during a power outage, you also treat it as a four-way stop)
posted by winston at 9:21 AM on September 5, 2005

The city of Houston will not adopt such a policy, however, said Wes Johnson, public works spokesman. Johnson explained there are concerns with safety and maintenance.

"Drivers do not understand the meaning of flashing lights,"

Fortunately up highway 290 in Austin we do understand the meaning of flashing lights. There are lights that are put on flash in the middle of the night. This it isn't at every light, but the ones that have very little crosstraffic. If the situation changes, they change the lights back.
posted by birdherder at 9:39 AM on September 5, 2005

Bonaldi:What does it mean when they flash? Is it that they're not in use, and traffic should behave as if there's no light there?

No. And that, question, right there, is why they don't use flashing lights in the city anymore.

A traffic signal that is flashing yellow in one direction and red in the other direction is a common sight in the country and small towns. The main road is flashing yellow, as a warning to drivers on that road that there is a cross street and there may be cross traffic, so they need to watch out, but they don't need to slow down. The cross road is flashing red, and drivers on that road come to a complete stop, wait until traffic on the main road clears, then proceed in the desired direction.
posted by jlkr at 10:16 AM on September 5, 2005

I always assumed that as technology to detect which lanes needed to proceed got better and cheaper, there was less need for flashing lights. That is to say: now, it's pretty easy and cheap to use pressure sensors in the pavement and/or cameras at the lights to detect when it's appropriate to change lights to let traffic move more freely. That, combined with the general lack of awareness about how to treat a flashing light (no excuses for that, merely pointing it out), means that it's in the best interest of a community to just rely on the sensors and keep a set of lights in service.
posted by delfuego at 11:03 AM on September 5, 2005

Up in Canada, I've seen flashing green traffic lights. What's that all about?
posted by Rash at 11:23 AM on September 5, 2005

Rash: Up in Canada, I've seen flashing green traffic lights. What's that all about?

It means your lane has the green, while opposing traffic is still read. It's the same as a left turn arrow, without the need for another bulb.
posted by Popular Ethics at 11:39 AM on September 5, 2005

read red *blush*
posted by Popular Ethics at 11:40 AM on September 5, 2005

In Ontario, anyways; in BC (or at least in Vancouver), flashing green lights mean proceed with caution, and are installed at intersections where the cross street doesn't have its own set of lights.
posted by chrominance at 12:18 PM on September 5, 2005

chrominance: thanks, I learned something new.
posted by Popular Ethics at 12:32 PM on September 5, 2005

Something I have always wondered:

When your light is flashing red, how do you know whether the other light is flashing red or yellow? Whether or not oncoming traffic is going to stop for me is something that I feel is important to know when reaching an intersection. I have seen lights that flash red all four ways and lights that flash yellow for one road.
posted by crabintheocean at 12:38 PM on September 5, 2005

crabintheocean: yeah, that always bugged me about flashing reds too, but your behaviour would be the same in both cases:
Stop. Make sure that cross traffic is either a) clear, or b) stopped, then proceed.
posted by Popular Ethics at 4:57 PM on September 5, 2005