A question when traffic lights switch to flashing red/flashing yellow mode

[MisterSG1]

This is something I've sort of wondered, around here in the GTA (and possibly all of Ontario), our traffic lights operate 24 hours a day, but I know of places that switch their traffic lights to yellow flash or red flash in the middle of the night.

The question I'm wondering is ambiguity, if we cannot see the cross traffic lights (which happens in many places which use four sided signals) how do we know what the right of way situation is after hours. If you don't follow what I mean, a flashing red of course tells the driver to stop, but on its own, it doesn't acknowledge who has right of way in the intersection.

Is there a specific law that when lights switch to red flash or yellow flash, that one side always has to have a yellow flash, or are there situations in the middle of the night where an intersection has all 4 directions face a red flash?

I wonder how many problems this causes, I mean do a quick Google search on the meaning of a flashing red on the internet, and there will be many sources that will say that a flashing red, in a single beacon flashing, or in a traffic light, means the same thing as a four way stop, this is definitely not always the case.

[doorknob60]

I was wondering the exact same thing earlier today, as I was thinking about an intersection in Nampa that is currently a 4 way stop, that there is talks about maybe making a signal. My argument against that is that for a lot of the day, it functions great as a 4 way stop. There aren't usually more than a few cars there at a time. But there's a few hours each day where a signal would be beneficial. I was pondering the possibility of it being a standard signal during peak hours, and a 4 way flashing stop at other times. Signals don't do that around here, but it was interesting for me to think about.

[peterj920]

In Appleton, WI all of the traffic signals along College Ave have flashing reds in the Downtown area.  The street is popular for teens to cruise, and there are a lot of pedestrians.  I think the reason why there aren't many all way flashing reds at night is because traffic engineers probably find it more beneficial to keep a signal operational if traffic is pretty equal coming from all parts of an intersection.  With the flashing yellow, the logic is that traffic shouldn't have to stop for few cars on side roads, and traffic has calmed down so a lone car can turn safely after stopping. 

[Jet380]

You're lucky you have traffic lights that go into flash mode at all... here in Australia all lights must operate 24/7 no matter what  . They are trialling a configuration where after around 10PM the intersection defaults to solid red on all approaches, only turning green after a car has arrived and come to a complete stop, the idea being to reduce travel speed and so enhance safety.

I guess if you can't see the other signal it's safest to assume the cross traffic isn't going to stop, which probably isn't such a bad idea in any case given you're more likely to be dealing with drunk or tired drivers during the small hours.

[mrsman]

In Appleton, WI all of the traffic signals along College Ave have flashing reds in the Downtown area.  The street is popular for teens to cruise, and there are a lot of pedestrians.  I think the reason why there aren't many all way flashing reds at night is because traffic engineers probably find it more beneficial to keep a signal operational if traffic is pretty equal coming from all parts of an intersection.  With the flashing yellow, the logic is that traffic shouldn't have to stop for few cars on side roads, and traffic has calmed down so a lone car can turn safely after stopping.

I agree.  That is my experience as well.  The only times I can recall that a signal is set to go to flashing mode is a flashing mode to red/yellow for the reason you describe above.  Prevent main street from having to stop at all and to give it absolute priority.  When two equivalent streets meet, there is usually enough traffic to justify a signal 24/7.

However, I have seen many signals malfunction.  Sometimes after a power outage a signal goes to flash mode before repairs can be made to get the signal fully functioning.  I recall seeing this in LA where there are very few signals that regularly go into flash, but every signal has a flash mode for malfunctions.  Where two main streets meet - all red flash. 

Here in suburban MD, most signals do flash from 1 am to 5:30 am.  I don't recall any signal flashing all-red.

[cbeach40]

This is something I've sort of wondered, around here in the GTA (and possibly all of Ontario), our traffic lights operate 24 hours a day, but I know of places that switch their traffic lights to yellow flash or red flash in the middle of the night.

The convention for Ontario is to run 24/7 and to go into all red flash if there is a fault.

The question I'm wondering is ambiguity, if we cannot see the cross traffic lights (which happens in many places which use four sided signals) how do we know what the right of way situation is after hours. If you don't follow what I mean, a flashing red of course tells the driver to stop, but on its own, it doesn't acknowledge who has right of way in the intersection.

Is there a specific law that when lights switch to red flash or yellow flash, that one side always has to have a yellow flash, or are there situations in the middle of the night where an intersection has all 4 directions face a red flash?

I wonder how many problems this causes, I mean do a quick Google search on the meaning of a flashing red on the internet, and there will be many sources that will say that a flashing red, in a single beacon flashing, or in a traffic light, means the same thing as a four way stop, this is definitely not always the case.

Which is why the convention here is what it is. Driver expectancy around here is that a flashing red is an all way stop, so flashing amber is definitely frowned upon.
Not to say it doesn't happen in some municipalities, but it is definitely not a good idea.

But as inferred in the OP, standard practice is to cycle 24 hours a day. Considering that a properly designed actuated signal should cycle to the side street almost instantly, that small delay is considered to be worth the clarity.

[1995hoo]

We used to have some lights in Fairfax City that went to a flashing cycle at night. They all served shopping centers. The thru street got flashing yellow and the shopping centers got flashing red. I thought that was pretty reasonable since there might have been at most maybe one business open 24 hours (a 7-11) in those shopping centers. They were gone at least by 2001 in favor of 24/7 signals.

[jeffandnicole]

I've noticed a few times at intersections where signals should be running 24/7, but are in flash mode due to a power outage or other issue: People have seemed to forget that the flashing yellow has the right of way.  I've seen where people will stop and treat it as a 4-way stop.  That's nice...but that's not the way it is supposed to be done!

[kphoger]

I've thought of this every so often. Some towns switch to red/yellow, others red/red, still others offer a mixed bag. If you can't see the cross-traffic signals, then there's no foolproof way knowing. As much as I dislike stoplights, I'd rather signals operate 24/7 than not know whether I can safely go or not.

[slorydn1]

Until about 15 years ago, all of the stoplights on US-17 (now US-17 Business) from River Bend all the way to downtown New Bern (except for the intersection at Broad St and Queen St) flashed yellow for mainline traffic and red for cross traffic from midnight until 6am. Now only a couple do, mostly in downtown New Bern. All of the rest are 24/7 stoplights.

I'm with kphoger, both on the dislike of, and feeling the need for normal operation 24/7.

Interestingly enough, however, we have more wrecks now from people a)slamming on brakes because the light went yellow and b) from people speeding up trying to beat the light than we ever did because of cross traffic running their flashing red at o-dark 30 #gofigure.

[mrsman]

Until about 15 years ago, all of the stoplights on US-17 (now US-17 Business) from River Bend all the way to downtown New Bern (except for the intersection at Broad St and Queen St) flashed yellow for mainline traffic and red for cross traffic from midnight until 6am. Now only a couple do, mostly in downtown New Bern. All of the rest are 24/7 stoplights.

I'm with kphoger, both on the dislike of, and feeling the need for normal operation 24/7.

Interestingly enough, however, we have more wrecks now from people a)slamming on brakes because the light went yellow and b) from people speeding up trying to beat the light than we ever did because of cross traffic running their flashing red at o-dark 30 #gofigure.

What you describe is not surprising.  People are used to driving down US 17 without stopping.  When the signals flashed, that would be the case - even with cross traffic present. Side traffic would simply have to yield. But now, people drive fast through green lights and don't expect any of them to turn yellow.  The disruption leads to more accidents.

[MisterSG1]

While brainstorming after reading a few posts, I think I know a solution that could possibly work to eliminate the ambiguity, unfortunately it would require a slight tweak of the rules.

Flashing Yellow - Proceed with caution (no change in meaning)
Flashing Red - Stop, this intersection is a FOUR WAY or ALL WAY stop
Flashing Red + Yellow - Stop, and proceed only if safe to do so, cross traffic has right of way

Of course for this to work, every solo red beacon out there across both Rural America and Canada would have to be tweaked to this new format, so it would be expensive, the phasing of the new definition would have to be implemented everywhere on the same date as to eliminate the ambiguity entirely (where some have the old definition of flashing red and some have the new definition of flashing red). Personally I see this as a possible solution to this issue and can keep overall traffic flow in better shape.

[cbeach40]

While brainstorming after reading a few posts, I think I know a solution that could possibly work to eliminate the ambiguity, unfortunately it would require a slight tweak of the rules.

Flashing Yellow - Proceed with caution (no change in meaning)
Flashing Red - Stop, this intersection is a FOUR WAY or ALL WAY stop
Flashing Red + Yellow - Stop, and proceed only if safe to do so, cross traffic has right of way

Of course for this to work, every solo red beacon out there across both Rural America and Canada would have to be tweaked to this new format, so it would be expensive, the phasing of the new definition would have to be implemented everywhere on the same date as to eliminate the ambiguity entirely (where some have the old definition of flashing red and some have the new definition of flashing red). Personally I see this as a possible solution to this issue and can keep overall traffic flow in better shape.

And a tweak to all of the existing signal controllers too. So, you're talking billions of dollars and countless working hours. And the transition period will undoubtedly create more collisions, and ensuing lawsuits, tying up even more resources and dollars.

All to do what? Save a handful of people a few seconds in the middle of the night?   

[kphoger]

Every solo red beacon out there across both Rural America and Canada would have to be tweaked to this new format, so it would be expensive, the phasing of the new definition would have to be implemented everywhere on the same date as to eliminate the ambiguity entirely (where some have the old definition of flashing red and some have the new definition of flashing red).

And a tweak to all of the existing signal controllers too. So, you're talking billions of dollars and countless working hours. And the transition period will undoubtedly create more collisions, and ensuing lawsuits, tying up even more resources and dollars.

All to do what? Save a handful of people a few seconds in the middle of the night?   

Well, sure, when you say it like that...  But, come on now, be realistic, those few seconds are pretty annoying!

[cbeach40]

Well, sure, when you say it like that...  But, come on now, be realistic, those few seconds are pretty annoying!

That's what a right turn followed by a U-turn are for! 

[kphoger]

Well, sure, when you say it like that...  But, come on now, be realistic, those few seconds are pretty annoying!

That's what a right turn followed by a U-turn are for! 

Except that, in at least some places, U-turns are not allowed intersections with no traffic control devices.  Which means you could get stuck at the exact same situation the next light down.

[cbeach40]

Well, sure, when you say it like that...  But, come on now, be realistic, those few seconds are pretty annoying!

That's what a right turn followed by a U-turn are for! 

Except that, in at least some places, U-turns are not allowed intersections with no traffic control devices.  Which means you could get stuck at the exact same situation the next light down.

My bad, I was meaning mid-block.

[kphoger]

Well, sure, when you say it like that...  But, come on now, be realistic, those few seconds are pretty annoying!

That's what a right turn followed by a U-turn are for! 

Except that, in at least some places, U-turns are not allowed intersections with no traffic control devices.  Which means you could get stuck at the exact same situation the next light down.

My bad, I was meaning mid-block.

Right, mid-block U-turns are the kind of thing that will get you a ticket around here.

[vdeane]

Why would someone thing flashing red meant "all-way stop" instead of simply "stop"?  Around here, they're almost always on rural roads, often with the other road having flashing yellow.

[cbeach40]

Why would someone thing flashing red meant "all-way stop" instead of simply "stop"?

Driver expectancy. Per:

Around here, they're almost always on rural roads, often with the other road having flashing yellow.

Whereas urban intersections will have an all-read flash sequence, converting it to an AWS in emergency. Therefore the situation is being applied inconsistently. And inconsistency is the worst situation possible when it comes to human factors in traffic engineering.

Right, mid-block U-turns are the kind of thing that will get you a ticket around here.

Well, changing one piece of ill-conceived legislation is far easier than changing signals across the board.   

[UCFKnights]

Why would someone thing flashing red meant "all-way stop" instead of simply "stop"?

Driver expectancy. Per:

Around here, they're almost always on rural roads, often with the other road having flashing yellow.

Whereas urban intersections will have an all-read flash sequence, converting it to an AWS in emergency. Therefore the situation is being applied inconsistently. And inconsistency is the worst situation possible when it comes to human factors in traffic engineering.

Right, mid-block U-turns are the kind of thing that will get you a ticket around here.

Well, changing one piece of ill-conceived legislation is far easier than changing signals across the board.   

Around here urban intersections still have one direction flashing yellow and one red. Seems like the easier solution would be to switch all intersections to have one direction to flashing yellow, as flashing red in all directions will cause delays, waste gas, and is all around less efficient.

[MisterSG1]

Why would someone thing flashing red meant "all-way stop" instead of simply "stop"?

Driver expectancy. Per:

Around here, they're almost always on rural roads, often with the other road having flashing yellow.

Whereas urban intersections will have an all-read flash sequence, converting it to an AWS in emergency. Therefore the situation is being applied inconsistently. And inconsistency is the worst situation possible when it comes to human factors in traffic engineering.

Right, mid-block U-turns are the kind of thing that will get you a ticket around here.

Well, changing one piece of ill-conceived legislation is far easier than changing signals across the board.   

Around here urban intersections still have one direction flashing yellow and one red. Seems like the easier solution would be to switch all intersections to have one direction to flashing yellow, as flashing red in all directions will cause delays, waste gas, and is all around less efficient.

I understand what you are getting at, one direction, suppose N/S is the "major street" and suppose E/W is the "minor street", this sounds good in theory, but what about when you get to situations where you have two streets that are equally "major". Think about when the two main perpendicular streets in such a town meet, who gets the flashing yellow and who gets the flashing red. Hence this is why some intersections in places that switch to flashing yellow/flashing red mode have intersections with all flashing reds.

Generally, in the GTA, the light on the major street will remain green indefinitely as long as no one waits for the light on the minor street. This does suck when you are on the minor street and have to wait for the light to cycle entirely through, unlike what cbeach40 says, you have to wait usually at least 30 seconds for the light to change, as the ped signals will have to display 15-30 hand flashes before the street turns yellow (depending on how big the intersection is).

Why would someone thing flashing red meant "all-way stop" instead of simply "stop"?  Around here, they're almost always on rural roads, often with the other road having flashing yellow.

There are a fair amount of the solo flashing beacons even in downtown Toronto, and there are ones where my brain wants to think that it means it's an all way stop, but it is not.....nearly made a mistake because of this. The flashing beacon on Richmond St (a one way that heads west, or in this case traffic moves to the right) is yellow, while the flashing beacon on Simcoe is red.

https://www.google.ca/maps/@43.6501412,-79.3872045,3a,15.7y,164.24h,87.3t/data=!3m6!1e1!3m4!1s3kY1dOPxT3PHwFmo14fUNQ!2e0!7i13312!8i6656?hl=en

A street I used to travel a lot when I went to go to Bolton, Healey Road, has a situation where you face two red flash beacons:

https://www.google.ca/maps/@43.8195639,-79.7751852,3a,62.3y,45.22h,90.16t/data=!3m6!1e1!3m4!1sMcVk0v9NMOAfZBQmFaaz2g!2e0!7i13312!8i6656?hl=en

This one at the intersection with Innis Lake Road (the northern continuation of Goreway Drive in Brampton) is an all way stop, so all four sides face the red flash.....but just 2 more intersections down you see this:

https://www.google.ca/maps/@43.8394778,-79.7552649,3a,15y,40.21h,89.37t/data=!3m6!1e1!3m4!1sbPwN73SPArlvF61vtxBMxg!2e0!7i13312!8i6656?hl=en

This intersection with The Gore Road is just a stop sign, with a red flash....thus the beacon on The Gore Road is a yellow flash, it's my humble opinion that the flashing lights seem to stand out more than the stop signs, and my brain processes them before the stop signs. Despite the flashing red on its own not showing who has right of way.

[roadfro]

I understand what you are getting at, one direction, suppose N/S is the "major street" and suppose E/W is the "minor street", this sounds good in theory, but what about when you get to situations where you have two streets that are equally "major". Think about when the two main perpendicular streets in such a town meet, who gets the flashing yellow and who gets the flashing red. Hence this is why some intersections in places that switch to flashing yellow/flashing red mode have intersections with all flashing reds.

Generally, in the GTA, the light on the major street will remain green indefinitely as long as no one waits for the light on the minor street. This does suck when you are on the minor street and have to wait for the light to cycle entirely through, unlike what cbeach40 says, you have to wait usually at least 30 seconds for the light to change, as the ped signals will have to display 15-30 hand flashes before the street turns yellow (depending on how big the intersection is).

To the first question, I would pick whichever "main" street happens to carry the most through traffic or the one that is a main, signed highway. In this kind of situation though, perhaps not converting to flash mode is better (depending on traffic levels and location).

To the second statement: If an intersection has ped buttons on all sides and detection on all approaches, the signal could run in "free" mode with default green to the main street. In the free mode, the signal is not dependent upon the typical cycle length as it's operating on demand (basically, first come first served). The ped signals wouldn't rest in walk but could change to walk immediately on activation (allow walk to start mid-green), and side street can also be served immdiately when cars/peds arrive (both assuming no conflicting movements detected). I don't know how often signals are operated in such a manner, but I believe most modern controllers have the necessary settings to make this work.

[UCFKnights]

Why would someone thing flashing red meant "all-way stop" instead of simply "stop"?

Driver expectancy. Per:

Around here, they're almost always on rural roads, often with the other road having flashing yellow.

Whereas urban intersections will have an all-read flash sequence, converting it to an AWS in emergency. Therefore the situation is being applied inconsistently. And inconsistency is the worst situation possible when it comes to human factors in traffic engineering.

Right, mid-block U-turns are the kind of thing that will get you a ticket around here.

Well, changing one piece of ill-conceived legislation is far easier than changing signals across the board.   

Around here urban intersections still have one direction flashing yellow and one red. Seems like the easier solution would be to switch all intersections to have one direction to flashing yellow, as flashing red in all directions will cause delays, waste gas, and is all around less efficient.

I understand what you are getting at, one direction, suppose N/S is the "major street" and suppose E/W is the "minor street", this sounds good in theory, but what about when you get to situations where you have two streets that are equally "major". Think about when the two main perpendicular streets in such a town meet, who gets the flashing yellow and who gets the flashing red. Hence this is why some intersections in places that switch to flashing yellow/flashing red mode have intersections with all flashing reds.

If traffic counts are equal, choose one direction at random. Its still better for traffic then the 4 way stop and eliminates the confusion.

[cbeach40]

Generally, in the GTA, the light on the major street will remain green indefinitely as long as no one waits for the light on the minor street. This does suck when you are on the minor street and have to wait for the light to cycle entirely through, unlike what cbeach40 says, you have to wait usually at least 30 seconds for the light to change, as the ped signals will have to display 15-30 hand flashes before the street turns yellow (depending on how big the intersection is).

So... 20-30 seconds (based on those hand flashes)? Cool.

And again, I did qualify that by saying properly actuated. Resting in walk is not doing it right.


[EDIT] - Thinking further on the numbers provided, if it takes 30 seconds to get a green, then that would mean that the *side road* is a good 25-36 m wide. Or to put it another way, 8-10 lanes wide.
Yeah, if that's the kind of cross section you're dealing with, then putting it under red flash is an astoundingly bad idea.

If traffic counts are equal, choose one direction at random. Its still better for traffic then the 4 way stop and eliminates the confusion.

If counts are equal, then properly actuated cycling won't be a significant problem in terms of delay. And making a call like that "at random" ?  Ummmmmmmm