Stoplight reset states. What's the deal?

This is something that has bugged me ever since I got my first car in the Chicago area (about 4 years ago). I grew up in an area without stoplights, and then didn’t have a car in college, so before then it was a non-issue.

Why is it, when the power goes out to a stoplight, and later comes back on, the default state is to have both sides flashing red? One of the most annoying things is to be stuck in traffic creeping along because a stoplight has decided to become a four way divided highway with left turn lane normal stop. Not to mention the human general confusion factor making things even worse. (Granted, some lights actually work better when implemented as four-way stops, but that’s beside the point).

I had some experience working with microcontrollers in college. It seems it wouldn’t be that difficult for them to have some EPROM hooked up to whatever controller they use, and when the power goes out, have the controller reset and reload the control program from the EPROM. The way I understand it’s currently done is they actually pay someone to go back out and reprogram the lights. This seems to be a waste of money and a cause of needless annoyance (not to mention the hard-to-measure factors associated with bumper-to-bumper stop-and-go traffic) as it can take up to 24 hours for them to do so.

Is there some element in the process I’m missing, or is it just a matter of the inefficiency of bureucracy?

Would you prefer that, when the power kicked back on, the lights shone green in all directions?

Traffic engineers – and no, IANATE – tend to lean toward the safe side when designing things like computerized traffic control systems, including light-controlled intersections. There are good reasons for this tendency, and I, for one, am thankful things are done this way. Sorry about your inconvenience, but the “4-way stop” sequence is the safest way of re-introducing signal control after a power outage.

Dude, you gotta move to a town where they pay the light bill. :smiley: I can’t recall ever having seen the phenomonon you describe, and I’ve been driving a LOT more than four years. In other words, it may have happened, but not often enough to stand out in my memory.

That, I think, is the answer to your question. Your experience notwithstanding, this isn’t a common enough problem to warrant the high-end engineering solution you suggest.

Actually I think that depends on where you live. Where I am I see traffic lights out at least once a month. I think it might have something to do with the amount of lightning we were gettingin the spring/summer.

How would what he suggested lead to that? The traffic lights have a default program: flashing red. What he’s suggesting is to change that default to a normal light pattern.

You must not live in an area where it storms. This is what causes the outages, and it can be pretty common, especially in the gulf coast.

One reason they might not want to do what you suggested, Hoopy, is because in areas where the lights are timed, the lights might not be sufficiently networked to re-time themselves, and must be re-timed manually. With short blocks, traffic can get pretty backed up when the lights aren’t synched. Having them flash red keeps traffic flowing (believe it or not) so that everyone eventually will get where they need to go.

But the most likely reason is cost and inefficiency. Why “upgrade” lights when they, for all intents and purposes, already work.

Fair enough. But I’ve lived in lots of different places. More-than-a-year residences in more than a dozen widely-dispersed cities, and mamy more shorter ones, albeit all (except a couple of the shorter ones) in urban or suburban areas. Not enough to consitute statistical proof, of course, but to me suggestive.

In case not clear, I was replying to Alien540.

I may be off base here, but I think the OP is wondering why the lights can’t just reload the original lighting program once power is restored. As if it can be stored in the ROM, or something.

I think a major reason why this isn’t possible is because most traffic signal systems aren’t that high-tech. They’re older model & aren’t sophisticated enough to contain memory chips with the signalling program on them. It’s much easier & basic for them to default to the flashing-red lights that you find so annoying.

I can understand the timing perspective, and the City of Chicago itself does time it’s lights so that you can go long periods without hitting a red light under normal traffic conditions (I think the speed is 27 mph).

But out here in the suburbs, they don’t bother. Everything operates off of sensors and/or independent timing mechanisms. I’ve yet to encounter a major suburb that seems to actually coordinate the timing of its lights.

Does the sequence revert to normal after some duration of 4-way flashing red? (I would assume it does).

It seems entirely sensible to do it that way to me; reverting straight back to normal could result in traffic streams getting a ‘green’ while individual vehicles from opposing streams were still attempting to cross (having already crossed the line) and committed themselves to traversing the junction.

Red signal in all directions is a good way of making sure that any traffic in already in transit through the junction has a chance to clear before the normal patter is resumed. Flashing red, I would assume is better because it grabs the attention of drivers and signifies that something unusual has happened - most drivers will instinctively slow down and pay more attention in response.

Tbone has it about right, though I don’t think the only alternatives are flashing red and all green. I can see it creating alot of problems if all of a sudden one direction gets a green light, other people may be in the intersection or something. Yes, it is probably overkill, but think how pissed you would be if there was an accident right in the middle of the intersection, just as the power came back on.

The sequence doesn’t revert to normal without someone coming out and physically resetting the box.

And as far as other being in the intersection when the lights would come back on, how is that a problem? If you know how to handle a four-way stop, it’s obvious who has the right-of-way. Those already in the intersection could easily clear out, since everyone should be starting out from a stationery position. Additionally, a green light does not give you the right to go. Illinois (and probably just about every other state) actually has written in the traffic laws that you are permitted to go on a green only after it is safe to do. In other words, if you proceed through an intersection when the light goes green, and someone decides at that moment to run the red and hits you, even though they will get the ticket, you technically could get a ticket as well, because you did not check to make sure it was safe to proceed.