An interesting traffic light concept...

[thenetwork]

Saw this link on Facebook...Interesting concept, but I doubt it would ever fly.

http://www.yankodesign.com/2010/11/18/sands-of-traffic-times/

[codyg1985]

How would one address protected left turns with this? What about color-blind people?

Neat concept, though.

[algorerhythms]

Here in São Carlos, Brazil, there are some traffic lights that display how much time remains in the cycle with a second green or red light that starts at the top of the signal and moves downward as the time runs out.

Aside from the colorblindness issue that codyg1985 pointed out, another flaw in the design in the link is that the yellow light cycle they suggest is ambiguous. The way they suggest doing the yellow light cycle, it's not possible to know whether the light is going from green to red or red to green.

[Alps]

Main problem is the reason the MUTCD bans countdowns on traffic signals - people racing to make the light vs. people trying to jump the light.

[Dr Frankenstein]

Quebec has countdowns on ped traffic lights, and I use them to get a good (or perfect in many cases) estimate on how much time is remaining on the main traffic light.

[mightyace]

^^^

Downtown Nashville has a few of those as well.

I also can "time" the light if I can see the light on the opposite direction.

[Bickendan]

Portland has countdown peds as well, but not all are tied directly to the mainline green phase.

[Quillz]

All the traffic lights near me now have pedestrian crossing countdowns. But since they're generally tied to the light itself, one can use it to time the length of a green light, too.

[iwishiwascanadian]

It's noticeable in DC, it's quite helpful. 

[Bryant5493]

I'd like to the see the red-yellow (amber) combo used here in the U.S., in anticipation of a green light.


Be well,

Bryant

[Icodec]

It's a good idea, I think. These are already in place on many pedestrian traffic signals, as in my town and many other places. I first noticed them when I went to DC 3 years ago.

[roadfro]

There are two inherent problems with this concept.

(1) The MUTCD currently bans countdown displays for vehicular traffic, as they can encourage drivers to speed up to pass the signal when they know the light is about to change.

(2) The way most traffic signal controllers in the U.S. are designed and operated, the length of the red or green phase is never constant. The phase length varies with a number of variables that can include vehicle actuation, passage gap timer (aka green extension), and also emergency vehicle/train/light rail preemption. With all these factors, a countdown can't be reliably estimated unless the signal is running in a pure fixed time mode...a practice that is somewhat discouraged except in evenly-spaced, synchronized downtown grids.


The use of countdown signals for pedestrian displays in the U.S. differs from the concept of a vehicular countdown display in that the pedestrian clearance interval (flashing don't walk - FDW) is always the same length--the FDW duration is derived by dividing the length of the crossing by an assumed walking speed (formerly 4 ft/s, now 3.5 ft/s in the MUTCD). A pedestrian countdown signal can be used by drivers to estimate when the adjacent green will change, but this is not always reliable as the vehicle green can often be extended beyond the end of the FDW.

[vdeane]

(2) The way most traffic signal controllers in the U.S. are designed and operated, the length of the red or green phase is never constant. The phase length varies with a number of variables that can include vehicle actuation, passage gap timer (aka green extension), and also emergency vehicle/train/light rail preemption. With all these factors, a countdown can't be reliably estimated unless the signal is running in a pure fixed time mode...a practice that is somewhat discouraged except in evenly-spaced, synchronized downtown grids.

Tell that to NY.  All of our signals are on timers during the day, and a good chunk of them remain on timers at night.  We don't even have emergency vehicle preemptions... we just let them run the red light.

[froggie]

A pedestrian countdown signal can be used by drivers to estimate when the adjacent green will change, but this is not always reliable as the vehicle green can often be extended beyond the end of the FDW.

There are also cases where the vehicle signal will turn red BEFORE the pedestrian signal counts down to zero.

[roadfro]

A pedestrian countdown signal can be used by drivers to estimate when the adjacent green will change, but this is not always reliable as the vehicle green can often be extended beyond the end of the FDW.

There are also cases where the vehicle signal will turn red BEFORE the pedestrian signal counts down to zero.

I believe there was previously an option to allow the FDW/countdown period to extend into the yellow and all-red period. This is no longer the case in the current MUTCD--the FDW must end before the red comes on (and it is preferred that the FDW end at the start of yellow). This allows pedestrians the same "all red" interval for clearing as vehicles.

[Sykotyk]

The problem with the current use of the yellow light is that it doesn't give truly adequate time to either clear the intersection or stop entirely before the light for larger vehicles at the posted speed. The only way to guarantee you'll stop in time is to stop for every green light and wait for the yellow-red-green sequence. If the yellow phase truly was a warning, the yellow phase would be 5-6 seconds long, rather than the 1-2 seconds I've seen in many places.


The problem with the argument that the countdown would cause people to race the light is that the yellow light does that already. It's sudden. And in that moment you have to decide if you can make it or if you must stop. Sometimes, you're stuck in the middle. Perfect speed not to make it, but too fast to stop without serious braking. If you gave a steady green/flashing yellow about 5 seconds before the steady yellow phase, you would allow people, especially larger vehicles, towing vehicles, etc. to know that the light is about to change. The light is still green when this decision is made. Rather than yellow when there is no knowing exactly how long that yellow light will last.

[agentsteel53]

There are also cases where the vehicle signal will turn red BEFORE the pedestrian signal counts down to zero.

I have never seen this happen.  does this involve an all-pedestrians phase?

[mightyace]

^^^

At least it used to, I remember some traffic lights in downtown Williamsport, PA used to go all red with four way walk lights.  They even had diagonal cross walks.  Now, this was back in the 70s or 80s, so there were no countdowns on the flashing don't walk lights.  Just proof that the all red for pedestrian crossing has been used.

I also have seen some traffic lights that solely control a cross walk.

[froggie]

There are also cases where the vehicle signal will turn red BEFORE the pedestrian signal counts down to zero.

I have never seen this happen.  does this involve an all-pedestrians phase?

No...just normal intersection phasing.  There's a few of these in DC.

[agentsteel53]

No...just normal intersection phasing.  There's a few of these in DC.

I've never noticed that.  that's good to know because I tend to use the white pedestrian signal with the counting down as an indicator that all is well for me too.

DC just has some really baffling traffic light arrangements.  It makes sense, I suppose, if you remember that it is a 1790s city layout, but even then, there seem to be some intersections that could stand to be re-timed.

[Mr_Northside]

At least it used to, I remember some traffic lights in downtown Williamsport, PA used to go all red with four way walk lights.

I also have seen some traffic lights that solely control a cross walk.

The intersection just down the street from me (Brighton Rd & Woods Run Ave.) had the pedestrian signals put in just a couple of years ago.  When actuated, they operate with an All Red phase for vehicles (and all the ped signals operate together, regardless of direction).  Despite the fact they're fairly new, they aren't "Countdown" signals.

Also in the city, Rt. 28 has a signal just for pedestrians (I think it's at a bus stop near the St. Nicholas Church).  This, of course, will be torn out soon for the Rt. 28 upgrade.  (And good riddance).

[roadfro]

The problem with the current use of the yellow light is that it doesn't give truly adequate time to either clear the intersection or stop entirely before the light for larger vehicles at the posted speed. The only way to guarantee you'll stop in time is to stop for every green light and wait for the yellow-red-green sequence. If the yellow phase truly was a warning, the yellow phase would be 5-6 seconds long, rather than the 1-2 seconds I've seen in many places.

The problem with the argument that the countdown would cause people to race the light is that the yellow light does that already. It's sudden. And in that moment you have to decide if you can make it or if you must stop. Sometimes, you're stuck in the middle. Perfect speed not to make it, but too fast to stop without serious braking. If you gave a steady green/flashing yellow about 5 seconds before the steady yellow phase, you would allow people, especially larger vehicles, towing vehicles, etc. to know that the light is about to change. The light is still green when this decision is made. Rather than yellow when there is no knowing exactly how long that yellow light will last.

A properly designed signal should not have a yellow phase duration of 1-2 seconds at all. Typical ranges for this are 3-6 seconds, based on an a formula from ITE that considers speed, reaction time and an assumed deceleration speed. These are also the bounds suggested (but not required) in the MUTCD.

What you're describing in that second paragraph is known in traffic engineering as the "dilemma zone". There is a distance from an intersection that, given a travel speed and reaction time, one can safely proceed through the intersection upon the onset of yellow. There is another distance at which under the same conditions that a driver can determine will have them stop at the stop line when the signal turns red. The area in between is the dilemma zone.

Adding any kind of blinking indication to a green light just before the the signal were to turn yellow would be implementing the same type of problem that any vehicle countdown display would...an advance notice of the yellow phase. This could lead to extending the dilemma zone even further, as that advance notice will be reacted to differently by different drivers. The potential for a bigger dilemma zone leads itself to higher numbers of accidents due to even more random nature of driver reaction to the signal.

[mhallack]

If I remember right in Tijuana, BC they had countdown signals at intersections, at least in the tourist areas (Avenida Revolucion) But it's been a while since I was last there.

Anyone dare go back to Tijuana to check this out? 

[Alps]

If I remember right in Tijuana, BC they had countdown signals at intersections, at least in the tourist areas (Avenida Revolucion) But it's been a while since I was last there.

Anyone dare go back to Tijuana to check this out? 

Our own agentsteel went down there not too long ago, and I believe he did verify their existence through photography.

[algorerhythms]

Here's a photo (not taken by me) of one of the countdown signals that I saw while in Recife.