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Author Topic: Traffic signal  (Read 847387 times)

Amtrakprod

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Re: Traffic signal
« Reply #4725 on: August 22, 2022, 07:37:21 AM »

So wouldn’t you argue that a FYA with ped protect to change the arrow red when the walk sign is activated by a pedestrian push button? That sounds most context appropriate for that location.

Until a pedestrian pushes the button, then just walks across on his own against the light after waiting for a few seconds and realizing there is no conflicting traffic anywhere near. Then by the time the walk signal activates and the arrow turns red, a handful of cars have arrived and now have to wait for no reason to make their left turn, which is not only annoying but also increases idling emissions.

This is a problem with HAWKs too, by the way. People push the button, get sick of waiting for the light to change, and jaywalk on their own as soon as a gap in traffic shows up. By the time the light does change, any pedestrians have long since crossed and left the scene.
We can give better pedestrian service at the signals you know. Make all the buttons “hot”, and trigger the signal right away.


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Re: Traffic signal
« Reply #4726 on: August 22, 2022, 11:05:42 AM »

I always tell them, you’re not mad at the button, you’re mad at the signal timing.

When a traffic signal is running under a coordinated plan, sometimes funny things can happen if splits don't cover any Ped phases fully (W+FDW+Y+AR), at least for an exclusive pedestrian phase and also if the force-off (Veh and PedApply) calculations are off. It's also dependent on what controller is on the field, as their software and methods can vary.

Broadway and Evans St in South Portland ME has a Trafficware Commander ATC controller and initially when the signal was retimed this June, Ped Phase 9 wouldn't get serviced at all when a call was placed. The new cycle lengths were half-cycled at 56s AM, 50s Md and 60s PM. The controller was still running the programmed split time (6-8s), however the ped phase (4 W) and clearance (30 FDW) would not be timed at all, resulting in the Ped phase getting skipped. Eventually after three cycles, the controller would detect that it hasn't serviced at all, resulting in the coordination plan failing and going into Free timing until the next programmed coordination pattern. While not the exact same thing as described below in this post... we did have instances of peds crossing against DW and lots of red light runners due to the controller acting wonky.

Until a pedestrian pushes the button, then just walks across on his own against the light after waiting for a few seconds and realizing there is no conflicting traffic anywhere near. Then by the time the walk signal activates and the arrow turns red, a handful of cars have arrived and now have to wait for no reason to make their left turn, which is not only annoying but also increases idling emissions.

This is a problem with HAWKs too, by the way. People push the button, get sick of waiting for the light to change, and jaywalk on their own as soon as a gap in traffic shows up. By the time the light does change, any pedestrians have long since crossed and left the scene.

Eventually it was discovered the following things caused this:
- The split for Phase 9 was too low (Must cover Min Green + Y + AR).
- No "dummy" phase was assigned to each side of the barrier in the coordinated ring (There was only a Phase 9 on Ring 1, nothing below on Ring 2).
- Stop-in-Walk (below) wasn't working correctly because of this - it only worked if Phase 5 (lagging prot left) was active and gapped out.
- Easy Calcs (default yield points, or window where phases can be serviced) weren't being calculated correctly (the yield calculation was resulting in a negative number).

The split for Phase 9 was bumped to 8s (W + AR), a "dummy" phase 13 was added to Ring 2 of the Ring/Barrier and the coordination strategy had to be changed from End to Begin of Green. In addition, since the Ped permissive window wasn't being calculated correctly, the Easy Calcs had to be manually calculated for the Veh/PedApply (permissive window) for all of the phases. Since these changes, there haven't been any issues with skipped peds causing long waits and causing the controller to fail the coord plan to go into Free.

Quote
Stop-In-Walk is a very important feature that allows the split time of a phase less than the minimum pedestrian requirements (sum of the walk + ped clearance + yellow + all-red clearance).

Stop-In-Walk causes the local cycle counter to “stop” during coordination if a force-off is applied to the phase and it is still timing walk or pedestrian clearance.

TL;DR: Broadway and Evans St in South Portland ME, under new Coordination plans, was skipping the exclusive Ped phase and failing Coord plans due to the split being too low and the controller incorrectly calculating when phases can be serviced, resulting in long ped wait times. Remedies were done to correct this issue and the intersection works as intended now with no more long ped waits or Coord Faults.
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Amtrakprod

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Re: Traffic signal
« Reply #4727 on: August 26, 2022, 10:09:01 PM »


Brand new signal, Cabot/1A/Dodge Beverly, MA


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Re: Traffic signal
« Reply #4728 on: August 26, 2022, 11:55:30 PM »

TL;DR: Broadway and Evans St in South Portland ME, under new Coordination plans, was skipping the exclusive Ped phase and failing Coord plans due to the split being too low and the controller incorrectly calculating when phases can be serviced, resulting in long ped wait times. Remedies were done to correct this issue and the intersection works as intended now with no more long ped waits or Coord Faults.

Thanks for the excellent explanation.  I've always been fascinated with coordinated traffic signal networks; one of my managers worked for Sperry on the development of their original system in downtown Miami.  It always seemed to me that conversion of an arterial corridor to one-way pairs would be necessary to balance the needs of [automobile] throughput and pedestrians.  The coordination of perpendicular arterials would be even harder.  In the rail transit industry, we have to perform detailed simulations and conduct appropriate analyses to get all of the [people flow] issues straightened out.
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jakeroot

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Re: Traffic signal
« Reply #4729 on: August 27, 2022, 01:05:32 PM »

TL;DR: Broadway and Evans St in South Portland ME, under new Coordination plans, was skipping the exclusive Ped phase and failing Coord plans due to the split being too low and the controller incorrectly calculating when phases can be serviced, resulting in long ped wait times. Remedies were done to correct this issue and the intersection works as intended now with no more long ped waits or Coord Faults.

Thanks for the excellent explanation.  I've always been fascinated with coordinated traffic signal networks; one of my managers worked for Sperry on the development of their original system in downtown Miami.  It always seemed to me that conversion of an arterial corridor to one-way pairs would be necessary to balance the needs of [automobile] throughput and pedestrians.  The coordination of perpendicular arterials would be even harder.  In the rail transit industry, we have to perform detailed simulations and conduct appropriate analyses to get all of the [people flow] issues straightened out.

This matter of coordinating perpendicular arterials has long fascinated me as well. Seems very, very hard to get right.

Bellevue, WA is pretty impressive. Tight, dense downtown core, but everything is two-way, mostly four to six lanes and dedicated turn signals (some FYA). On one hand, getting around doesn't require much thought, back-tracking, etc like you might see in Seattle, but the timing of the signals is just ridiculously impressive. I don't know how they do it so well. Obviously a lot of lead-lag and some automatic WALK.



https://uploads.tapatalk-cdn.com/20220827/f418ddbbdaeb820d9f21c58dca75fb61.jpg
Brand new signal, Cabot/1A/Dodge Beverly, MA

I love Mass's commitment to yellow signal poles. At least in some places. Don't even see that in MN anymore.

Are there other emergency beacons for the additional approaches, or do the other signals just go red? Hard to tell without seeing in person, I suppose.
« Last Edit: August 27, 2022, 01:08:09 PM by jakeroot »
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kirbykart

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Re: Traffic signal
« Reply #4730 on: August 27, 2022, 01:51:28 PM »

jakeroot

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Re: Traffic signal
« Reply #4731 on: August 27, 2022, 02:06:34 PM »

kirbykart

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Re: Traffic signal
« Reply #4732 on: August 27, 2022, 02:07:56 PM »

Amtrakprod

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Re: Traffic signal
« Reply #4733 on: August 27, 2022, 09:03:48 PM »

TL;DR: Broadway and Evans St in South Portland ME, under new Coordination plans, was skipping the exclusive Ped phase and failing Coord plans due to the split being too low and the controller incorrectly calculating when phases can be serviced, resulting in long ped wait times. Remedies were done to correct this issue and the intersection works as intended now with no more long ped waits or Coord Faults.

Thanks for the excellent explanation.  I've always been fascinated with coordinated traffic signal networks; one of my managers worked for Sperry on the development of their original system in downtown Miami.  It always seemed to me that conversion of an arterial corridor to one-way pairs would be necessary to balance the needs of [automobile] throughput and pedestrians.  The coordination of perpendicular arterials would be even harder.  In the rail transit industry, we have to perform detailed simulations and conduct appropriate analyses to get all of the [people flow] issues straightened out.

This matter of coordinating perpendicular arterials has long fascinated me as well. Seems very, very hard to get right.

Bellevue, WA is pretty impressive. Tight, dense downtown core, but everything is two-way, mostly four to six lanes and dedicated turn signals (some FYA). On one hand, getting around doesn't require much thought, back-tracking, etc like you might see in Seattle, but the timing of the signals is just ridiculously impressive. I don't know how they do it so well. Obviously a lot of lead-lag and some automatic WALK.



https://uploads.tapatalk-cdn.com/20220827/f418ddbbdaeb820d9f21c58dca75fb61.jpg
Brand new signal, Cabot/1A/Dodge Beverly, MA

I love Mass's commitment to yellow signal poles. At least in some places. Don't even see that in MN anymore.

Are there other emergency beacons for the additional approaches, or do the other signals just go red? Hard to tell without seeing in person, I suppose.
1. Bellevue May be great for driving timing, but it took forever to bike through. They have some long signal cycles!

2. Yes! i love the yellow poles too. Here's another perspective:


only one approach has the HAWK, but i imagine when it’s activated the signal gives a clearance at the signal behind it and all the other approaches go all red.


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Scott5114

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SignBridge

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Re: Traffic signal
« Reply #4735 on: August 28, 2022, 08:25:47 PM »

Wonder why that one head is mounted horizontal while the rest are all vertical.
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Re: Traffic signal
« Reply #4736 on: August 28, 2022, 08:45:22 PM »

That is extremely common in Nebraska. The side-by-side (aka Colorado-style doghouse) left turn with horizontal through signal heads is widespread there, and you can find some legitimate doghouses too (example). Wonder if they used a Nebraska-based contractor.

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Re: Traffic signal
« Reply #4737 on: August 28, 2022, 08:51:31 PM »

I don't get it. What is the reason or purpose for that configuration or is it just odd local practice? If they like horizontal why not make the shared left-turn head a horizontal also, like in Texas?
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roadman65

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Re: Traffic signal
« Reply #4738 on: August 29, 2022, 08:33:08 AM »

https://goo.gl/maps/C9Py3icAWDEhE2sG6
I was noticing on the horizontal mounts, the green arrow lens is second to last and not last as it would be vertically.

This photo shows the four section horizontally and vertically in Galloway, NJ.
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Re: Traffic signal
« Reply #4739 on: August 29, 2022, 09:31:39 AM »

https://goo.gl/maps/C9Py3icAWDEhE2sG6
I was noticing on the horizontal mounts, the green arrow lens is second to last and not last as it would be vertically.

This photo shows the four section horizontally and vertically in Galloway, NJ.

Standard layout as per the MUTCD.

https://mutcd.fhwa.dot.gov/htm/2003r1/part4/fig4d-03_longdesc.htm
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Re: Traffic signal
« Reply #4740 on: August 29, 2022, 09:36:10 AM »

I don't get it. What is the reason or purpose for that configuration or is it just odd local practice? If they like horizontal why not make the shared left-turn head a horizontal also, like in Texas?

I've heard of mounting a left turn signal differently than the through signals, maybe for distinction. I know Lawton, OK used to have a regular thing where the left turn signal would be horizontal while everything else was vertical, but I think they might have moved to all horizontal now as I'm having a hard time finding an example on streetview. Pretty sure I've seen the same thing somewhere in Alberta too. There is also this one-off in Albuquerque with vertical left turn signal and horizontal otherwise.

I've been to plenty of places that use horizontal signals regularly (NM, TX, FL, NE, parts of LA, AL, OK...) and this is the first I've ever seen a doghouse signal on the same mast as horizontal signals in someplace that's not Nebraska. Seems to be a Nebraska-specific oddity. I agree though that it doesn't make much sense - if the point of horizontal signals is a lower wind profile, a doghouse backplate is basically a sail which kind of defeats the purpose...

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Re: Traffic signal
« Reply #4741 on: August 29, 2022, 09:41:40 AM »

https://goo.gl/maps/C9Py3icAWDEhE2sG6
I was noticing on the horizontal mounts, the green arrow lens is second to last and not last as it would be vertically.

This photo shows the four section horizontally and vertically in Galloway, NJ.

Standard layout as per the MUTCD.

https://mutcd.fhwa.dot.gov/htm/2003r1/part4/fig4d-03_longdesc.htm

Yeah, the arrows are supposed to be positioned on the same side of the green light as the direction they're indicating, which is why the left- and right-turn horizontal 5 section signals have the green in a different place (example).

SkyPesos

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Re: Traffic signal
« Reply #4742 on: August 29, 2022, 09:44:33 AM »

Some places in Alberta (namely Edmonton, but there's probably some others) also do something like that; mounting a left turn signal vertically and the rest horizontally. They also do the double red light thing Texas does.

https://goo.gl/maps/i7heX9Yfiq1axoYr8
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Re: Traffic signal
« Reply #4743 on: August 29, 2022, 11:16:06 AM »

I've been to plenty of places that use horizontal signals regularly (NM, TX, FL, NE, parts of LA, AL, OK...) and this is the first I've ever seen a doghouse signal on the same mast as horizontal signals in someplace that's not Nebraska. Seems to be a Nebraska-specific oddity. I agree though that it doesn't make much sense - if the point of horizontal signals is a lower wind profile, a doghouse backplate is basically a sail which kind of defeats the purpose...

Both the eastbound and westbound approaches to this intersection in Yakima, Washington have a doghouse left turn signal with a horizontal supplemental through signal, like the Nebraska example:

https://goo.gl/maps/ozubAUPs3wtS6Daj6

I think there are more. This is just the one I saved. Yakima was a big user of horizontal signals, possibly the only city in Washington that did it regularly. So there are some oddities out there.

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Re: Traffic signal
« Reply #4744 on: August 29, 2022, 02:20:42 PM »

Are there any horizontal doghouses out there? I sure hope not because that shit would look crazy  :-D
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SkyPesos

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Re: Traffic signal
« Reply #4745 on: August 29, 2022, 02:25:32 PM »

Are there any horizontal doghouses out there? I sure hope not because that shit would look crazy  :-D
Not a doghouse like what we’re used to in the states, but Japan’s horizontal signals with the protective-permissive arrows below the standard RYG balls for turns are the closest I can think of for a “horizontal doghouse”.
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Re: Traffic signal
« Reply #4746 on: August 29, 2022, 02:30:24 PM »

Example:



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Re: Traffic signal
« Reply #4747 on: August 29, 2022, 04:18:42 PM »

Example:



I don't understand why they would have the red ord and green up arrow illuminated at the same time. Is that normal there?
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SkyPesos

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Re: Traffic signal
« Reply #4748 on: August 29, 2022, 04:40:11 PM »

Example:

[img snipped]

I don't understand why they would have the red orb and green up arrow illuminated at the same time. Is that normal there?
Yes, it's normal there. It's their way of signaling protected only right turns (equivalent to our left turns as Japan drives on the left). Think of it as "red light except if your direction has a green arrow" for Japanese traffic lights in general, and it would make a bit more sense.

Though this signaling results in some oddities like the left arrow and pedestrian light on the left side both on green (so left turn cars still have to yield to pedestrians), which I've seen zero other cases of.
« Last Edit: August 29, 2022, 04:51:43 PM by SkyPesos »
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Re: Traffic signal
« Reply #4749 on: August 29, 2022, 09:10:01 PM »

Yakima was a big user of horizontal signals, possibly the only city in Washington that did it regularly.

Have they switched to vertical signals on new installs now? I just poked around a bit on street view and the horizontal ones are everywhere, including on some new-looking signals...which is weird to me in because I had no idea Yakima used them to begin with. Nobody's ever mentioned it on here to my knowledge, and I've even been to Yakima before and feel like I would have remembered such a thing.


 


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