Night Flash

[PColumbus73]

What are your thoughts on traffic signals going on flash mode during non-peak hours, for instance, 1AM-5AM? Here in Myrtle Beach, traffic is really light between those hours and yet all the signals operate as usual. I think, at least in this area, night flash would be a good thing on roads with speed limits below 55mph. I think even intersections with dual-left turns could go on night flash as long as they aren't two arteries. Maybe keep a few signals in normal operation to keep people getting too complacent.

[Pink Jazz]

What are your thoughts on traffic signals going on flash mode during non-peak hours, for instance, 1AM-5AM? Here in Myrtle Beach, traffic is really light between those hours and yet all the signals operate as usual. I think, at least in this area, night flash would be a good thing on roads with speed limits below 55mph. I think even intersections with dual-left turns could go on night flash as long as they aren't two arteries. Maybe keep a few signals in normal operation to keep people getting too complacent.

It seems to be mostly a practice in rural areas as far as I know.  Occasionally I have seen some signals at shopping centers go into night flash mode as well.

[hotdogPi]

I have heard that it is more of a European thing.

[Pete from Boston]

It happens here and there around here.  Seems less common than it was.  Some of them still flash when it rains, though. 

[1995hoo]

Some of the lights in Fairfax City used to do it. I don't know if they still do. Made sense to me at the smaller intersections.

[cl94]

NYSDOT seems to be doing away with it as signals are replaced/retimed/adjusted. One near my parents' house flashed 11 PM - 5 AM until ~2010 (it was subsequently replaced a year or two later). Flashing makes sense for a timed installation when the side street would get a green if no cars are waiting. With the increase in actuated signal installations, there's no reason to have a flashing period because a side street will never get a green if there isn't a vehicle present and it's safer to make all vehicles wait for a green light, nor will the major road get a long green if it is vacant and several cars are waiting on the minor road. With the aggressive signal upgrades going on around here, just about every timed signal outside of an incorporated city no longer exists or operates as such.

Here, at least, night flashing is typically restricted to business parks (older installations where the light only operates on weekdays, becoming rarer) and inner-city locations where signals are timed according to pedestrian usage and traffic flow purposes. I've also seen it at schools, but these locations are switching over as well.

[UCFKnights]

They've been disappearing around here too. I miss them and think more of them should do it... drives me nuts at night when I have to stop at every light for one car on a side road, a stop sign equivalent would easily be more than adequate and makes night time travel much faster. Also there frequently is a minimum time between cycles for the side street, so one car goes, I'm not close enough to go on the same green and am stuck waiting, even though there is no traffic around at all. Infact, I personally would like the law to be changed to red light means stop and other people have right of way, but you can proceed when safe and yielding to everyone else without a green.

[1995hoo]

They've been disappearing around here too. I miss them and think more of them should do it... drives me nuts at night when I have to stop at every light for one car on a side road, a stop sign equivalent would easily be more than adequate and makes night time travel much faster. Also there frequently is a minimum time between cycles for the side street, so one car goes, I'm not close enough to go on the same green and am stuck waiting, even though there is no traffic around at all. Infact, I personally would like the law to be changed to red light means stop and other people have right of way, but you can proceed when safe and yielding to everyone else without a green.

It's probably a separate discussion, but this raises the old question of what you do when it's 2:00 AM and you're at a red light and there's no other traffic around on any of the streets.

[kkt]

Palo Alto, CA, has signals flashing at night along University Avenue.  Or at least they did, I haven't checked in the last couple of years.

[hbelkins]

It's probably a separate discussion, but this raises the old question of what you do when it's 2:00 AM and you're at a red light and there's no other traffic around on any of the streets.

Turn right and then U-turn. 

[cpzilliacus]

I have seen an interesting practice at urban intersections in the overnights in Finland - flash yellow in all four directions (in which case the "yield to the vehicle on your right" rule applies).

[cpzilliacus]

It's probably a separate discussion, but this raises the old question of what you do when it's 2:00 AM and you're at a red light and there's no other traffic around on any of the streets.

Thought about that more than once in D.C., where no flashing signals are used except in very unusual circumstances.

[Brandon]

It's probably a separate discussion, but this raises the old question of what you do when it's 2:00 AM and you're at a red light and there's no other traffic around on any of the streets.

Get stopped by a hick New Jersey cop for stepping into the intersection.  (think Harold & Kumar)

[briantroutman]

The FHWA would appear to be discouraging the use of overnight flashing modes for signals because at least one study shows a statistically significant reduction in crashes when signals remain in normal mode, even during low volume periods.

I definitely see fewer overnight flashing signals than I used to, but I always assumed that was a result of more signals being controlled by sensor loops versus timers. With sensors, I see little reason to use an overnight flashing mode.

Somewhat related question: Do you know of any signals that have (or had) a low-volume flashing period that wasn't primarily in the overnight hours? I recall a signal near an industrial building (both the building and the signal have since been removed) where the signal flashed in all four directions all of the time, except at the beginnings and ends of shifts.

[Brian556]

Operating signals in flash mode can be problematic for a few reasons.

1. Signals operation in flash mode can be confusing just for the simple reason that it is not the traffic control method drivers are used to at said intersection.

2. If only two directions have flashing red, it can be confusing.
Drivers could easily mistake it for all-way flashing red. This awkwardness is more apparent at locations where it feels like all directions should flash red because both roads feel equal, but only one street has flashing red.
There are some locations around here where the way it is set up does not feel right. Example: I-35E at Corinth Pkwy. Corinth Pkwy gets flashing yellow, but frontage roads get flashing red. To me, both are equal, and it should flash red in all directions.

3. Often, drivers stop at flashing yellows. Either they are colorblind, drunk, or ignorant of traffic laws.

4. Many intersections have restricted visibility that is not problematic when signals are operating, but is problematic in non-all-way-red flash mode situations.

I defiantly can see how flash mode could contribute to accidents.
I do think it's safer to not use flash mode, even if it increases delay. However, delay can be minimized due to modern detection methods.
Driving at night is already way more hazardous than during the daytime, and signals in flash mode just add to the danger.

I think the FHWA has the right idea on this one.

[kkt]

I do think it's safer to not use flash mode, even if it increases delay. However, delay can be minimized due to modern detection methods.

If the primary direction is flashing yellow, that traffic can just continue at a slow cruising speed.  A loop detector would require stopping and then accelerating again.  Yes, drivers at the cross street have to be clued enough to realize that the main direction doesn't stop...

[texaskdog]

Excellent idea.  I HATE waiting for stoplights that aren't needed.  Some lights are only needed at all during work hours. 

[tdindy88]

Still plenty of them around Indianapolis. Hell where I live there's three intersections within a mile of me that flash during the overnight hours from 11pm to 6am and for the most part I love it. It probably helps that two of the three intersections are 3-ways.

[theline]

Somewhat related question: Do you know of any signals that have (or had) a low-volume flashing period that wasn't primarily in the overnight hours? I recall a signal near an industrial building (both the building and the signal have since been removed) where the signal flashed in all four directions all of the time, except at the beginnings and ends of shifts.

Yes, I clearly recall signals that were in flash mode at all times, except for shift change at industrial plants, though I can't think of any that still exist. There used to be a plant along West Sample Street in South Bend that had such a signal. I can't recall the name of the factory, but it's building has been demolished and the signal is long gone.

In Muncie, Warner Gear used to have multiple flashing signals along Kilgore Ave. (SR-32). GSV shows the plant closed and lights gone.

I believe that some of these signals may have been controllable to some degree by the plant guard in the shack by the signal. He may have been able to press a button to request a signal change, much as the pavement loops do today.

[Big John]

Somewhat related question: Do you know of any signals that have (or had) a low-volume flashing period that wasn't primarily in the overnight hours? I recall a signal near an industrial building (both the building and the signal have since been removed) where the signal flashed in all four directions all of the time, except at the beginnings and ends of shifts.

In Wauatosa, WI, the signals are like that for Capitol Ave at the Harley Davidson plant.

[roadfro]

If the primary direction is flashing yellow, that traffic can just continue at a slow cruising speed.  A loop detector would require stopping and then accelerating again.

Not necessarily. It will depend on speeds and placement of the detector. A detector upstream of the signal can trip the light before the car gets to the stop line...

[roadfro]

Somewhat related question: Do you know of any signals that have (or had) a low-volume flashing period that wasn't primarily in the overnight hours?

Center St and Mill St in downtown Reno NV flashes pretty much all the time. Here, Mill is only one block on the west side of Center, and the east leg has been replaced by parking lot access to a hotel/casino, so the Mill side flashes red while Center flashes yellow. Every once and a while, they put the signal in steady stop/go mode to accommodate traffic patterns due to construction or street festival closures in downtown--but I've only seen this done less than 5 times in 13ish years.

[tradephoric]

I do think it's safer to not use flash mode, even if it increases delay. However, delay can be minimized due to modern detection methods.

It's great to imagine an adaptive signal that cycles the side-street only when a vehicle is detected.  In reality, a few detectors will fault out (and won't be addressed in a timely manner) and an adaptive signal will turn into a fixed time signal pretty fast. 

[PColumbus73]

I would prefer flash mode, because there have been a couple times when I have been the only car on the primary road and have a car on a side street trip the detector (it's worst when cars on the side street are making a right turn.) It can be obnoxious.

[renegade]

It's probably a separate discussion, but this raises the old question of what you do when it's 2:00 AM and you're at a red light and there's no other traffic around on any of the streets.

Turn right and then U-turn. 

That does NOT work if there is a sign present which says "no turn on red" or "no U-turn"