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Author Topic: Traffic signal  (Read 847381 times)

jakeroot

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Re: Traffic signal
« Reply #4750 on: August 29, 2022, 10:32:48 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.

They are still being installed yes. The newest signal I know of, Ahtanum and 64th, was activated within the last two years, and only the supplemental signals on the poles are vertical, with the overhead signals being horizontal.

https://goo.gl/maps/bb2PG6SEEHtjFTKn7

Yakima has definitely used vertical signals in the past, and has continued to install them from time to time. But they are rarer, and I don't know the rationale behind their usage.

It should be noted that signals in Washington that are on state highways are generally maintained by WSDOT, and will match WSDOT standards. Even in Yakima, where horizontal signals are king, WSDOT-maintained signals will be vertical. This is always true, unless that particular signal was negotiated to be installed and/or maintained by the local agency. In which case, the standards can match the local rules. In the case of Yakima, I believe all traffic lights at the end of the I-82 and US-12 ramps are WSDOT installed and maintained, so are all vertical. Unless you ventured quite a ways off the freeway, it's likely you saw mostly vertical signals.
« Last Edit: August 29, 2022, 10:42:48 PM by jakeroot »
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roadfro

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Re: Traffic signal
« Reply #4751 on: September 01, 2022, 04:49:15 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.

I took undergrad and graduate courses in traffic engineering while in college. Even though I'm not a practicing engineer, I still find it fascinating--and signal coordination strategies among the most fascinating elements. There's a lot to balance, and it's not always easy to achieve that balance.

For two-way road networks, a lot of that balance is lead-lag phasing and adjusting cycle offsets. For grids, sometimes you just have to put in an occasional "bump" because it's just not possible to keep up a progression wave over multiple miles when you have multiple coordinated corridors. Plenty of tinkering around with Synchro and similar programs, and also trial and error...
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fwydriver405

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Re: Traffic signal
« Reply #4752 on: September 05, 2022, 10:27:40 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”.

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?

Some older signals in Massachusetts, particually in Cambridge and Everett have similar configurations to how the Japanese signalling system works, albeit in a vertical 4-section setup. The one in Everett I believe used to run lead-lag (or runs a different phase sequence based on time of day) but when I went to visit that intersection, it ran the typical lead-lead setup. Signals below...

Cambridge, at Massachusetts Ave at Hollis and Dover St (not my video):



Everett, at MA Route 16 and Everett Av, used to run different phasings in the past 30-35+ years but mostly lead-lead for the most part. Believe the bimodal arrow is new, older videos show it using the yellow ball for clearence like in Japan:

July 1988 (Appears to run lead-lead phasing. Notice how the yellow ball clears out the green arrow - Begin of Video): May 2019 (go to 12:52 for the phasing, which may appear to run lead-lag): August 2022 (photos only):


« Last Edit: September 05, 2022, 10:48:05 PM by fwydriver405 »
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plain

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Re: Traffic signal
« Reply #4753 on: September 06, 2022, 09:02:54 AM »

Those are wild. I've been to MA twice but don't recall seeing signals like that. I would think a lot of visitors would be a bit confused from the up arrow and red orb combo like that.

The phasing in the Cambridge example is especially interesting.
« Last Edit: September 06, 2022, 09:05:05 AM by plain »
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Re: Traffic signal
« Reply #4754 on: September 06, 2022, 10:10:38 AM »

Those are wild. I've been to MA twice but don't recall seeing signals like that. I would think a lot of visitors would be a bit confused from the up arrow and red orb combo like that.

Count me among those people. That cannot be MUTCD compliant.

fwydriver405

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Re: Traffic signal
« Reply #4755 on: September 06, 2022, 10:20:41 AM »

Those are wild. I've been to MA twice but don't recall seeing signals like that. I would think a lot of visitors would be a bit confused from the up arrow and red orb combo like that.

Count me among those people. That cannot be MUTCD compliant.

At least for the Everett example:

Quote from: MUTCD 2009 Edition Chapter 4D. Traffic Control Signal Features - Section 4D.05 Application of Steady Signal Indications
Standard:
10 The following combinations of signal indications shall not be simultaneously displayed on any one signal face:

CIRCULAR RED with CIRCULAR YELLOW;
CIRCULAR GREEN with CIRCULAR RED; or
Straight-through GREEN ARROW with CIRCULAR RED
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SignBridge

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Re: Traffic signal
« Reply #4756 on: September 06, 2022, 08:19:35 PM »

It's a Massachusetts thing. They don't concern themselves with that pesky MUTCD when maintaining old installations. They just do what they've done for the last hundred years..........

Are there any flashing green traffic lights still operating in Massachusetts?
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BlueOutback7

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Re: Traffic signal
« Reply #4757 on: September 06, 2022, 08:28:21 PM »

Are there any flashing green traffic lights still operating in Massachusetts?

There’s still a few here and there, mostly along the North Shore. There’s one in Stoneham on Pond Street next to the Stone Zoo. Another one on North Avenue in Wakefield was recently taken out of service with recent road work in the area.
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PurdueBill

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Re: Traffic signal
« Reply #4758 on: September 14, 2022, 10:00:11 AM »

It's a Massachusetts thing. They don't concern themselves with that pesky MUTCD when maintaining old installations. They just do what they've done for the last hundred years..........

Are there any flashing green traffic lights still operating in Massachusetts?

The remaining crazy ones with straight green arrows on with red circles and stuff are most often vestiges of past MDC installs.  DCR carried on the craziness and even though the gray paint job ones are slowly going away as seen in the Revere Beach Parkway examples above, the layout and timing stays the same. 

Salem even went so far a few years back as to upgrade an intersection that used to have one or two ground-mount signals (oddly, only one for the main drag and two for the cross street each direction) featuring flashing green and the old red-yellow pedestrian phase to have overhead flashing green signals too. 
And there is the famous new install within the last 5 years in Quincy of flashing greens replacing bottom yellow flashing heads. 
It is sad that the Wakefield ones are gone....they looked like they might last forever.
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SignBridge

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Re: Traffic signal
« Reply #4759 on: September 14, 2022, 07:45:44 PM »

Interesting.........where is the recent flashing green installation in Quincy?
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Amtrakprod

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Re: Traffic signal
« Reply #4760 on: September 14, 2022, 10:53:06 PM »

Are there any flashing green traffic lights still operating in Massachusetts?

There’s still a few here and there, mostly along the North Shore. There’s one in Stoneham on Pond Street next to the Stone Zoo. Another one on North Avenue in Wakefield was recently taken out of service with recent road work in the area.
Good to know about the North Avenue one. Glad I filmed it once awhile back, but sad I never got back to it


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Re: Traffic signal
« Reply #4761 on: September 14, 2022, 10:55:50 PM »

Are there any flashing green traffic lights still operating in Massachusetts?

There’s still a few here and there, mostly along the North Shore. There’s one in Stoneham on Pond Street next to the Stone Zoo. Another one on North Avenue in Wakefield was recently taken out of service with recent road work in the area.
Good to know about the North Avenue one. Glad I filmed it once awhile back, but sad I never got back to it


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Sign from Wakefield’s installation


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fwydriver405

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Re: Traffic signal
« Reply #4762 on: September 14, 2022, 11:11:57 PM »

Interesting.........where is the recent flashing green installation in Quincy?

Could this be the one? If so, this is on School St at Hancock St:


Curious to see if the Brockton one is still active as of the writing of the post. Not a flashing green, but still has the old style R-Y exclusive ped phase.

« Last Edit: September 14, 2022, 11:23:03 PM by fwydriver405 »
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Amtrakprod

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Re: Traffic signal
« Reply #4763 on: September 14, 2022, 11:34:59 PM »

Interesting.........where is the recent flashing green installation in Quincy?

Could this be the one? If so, this is on School St at Hancock St:


Curious to see if the Brockton one is still active as of the writing of the post. Not a flashing green, but still has the old style R-Y exclusive ped phase.

Brockton signal looks unchanged on street view (South/Main)

Malden and Everett has a handful of those signals too.


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kirbykart

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Re: Traffic signal
« Reply #4764 on: September 15, 2022, 09:57:21 AM »

What in the world is the purpose of a flashing green signal?!

kphoger

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Re: Traffic signal
« Reply #4765 on: September 15, 2022, 10:16:06 AM »

What in the world is the purpose of a flashing green signal?!

Depends where you are when you see it.

1.  In Mexico, it means the light is about to turn yellow.

2.  In some parts of Canada, it means your direction of traffic has a protected left.

3.  In other parts of Canada, it means you're at a crosswalk whose ped phase isn't active at the moment.

4.  In Massachusetts, it isn't defined by law but is similar to (3) above, but could be found anywhere that may require extra caution—not just at crosswalks.
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Re: Traffic signal
« Reply #4766 on: September 15, 2022, 01:28:26 PM »

What in the world is the purpose of a flashing green signal?!
3.  In other parts of Canada, it means you're at a crosswalk whose ped phase isn't active at the moment.

4.  In Massachusetts, it isn't defined by law but is similar to (3) above, but could be found anywhere that may require extra caution—not just at crosswalks.
A flashing yellow should be used in these examples. The bolded portion is literally the definition of where a flashing yellow should be used.
The Mexico one is interesting though.

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Re: Traffic signal
« Reply #4767 on: September 15, 2022, 04:16:37 PM »

What in the world is the purpose of a flashing green signal?!

Depends where you are when you see it.

1.  In Mexico, it means the light is about to turn yellow.

2.  In some parts of Canada, it means your direction of traffic has a protected left.

3.  In other parts of Canada, it means you're at a crosswalk whose ped phase isn't active at the moment.

4.  In Massachusetts, it isn't defined by law but is similar to (3) above, but could be found anywhere that may require extra caution—not just at crosswalks.
I think flashing green needs a definition in the US. I’d like to use them anywhere where through traffic has priority but other vehicles may be entering. Flashing yellow now seems more like a yield, bc of the FYA.


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jakeroot

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Re: Traffic signal
« Reply #4768 on: September 15, 2022, 04:21:28 PM »

Yeah, this notion that flashing green should ever be replaced by flashing yellow is nonsense. Canada and Mexico allow flashing green and it's used in very clever and helpful ways. The FHWA, in my opinion, shoots itself in the foot by not allowing it. They would be wise to reconsider.

I think flashing green needs a definition in the US. I’d like to use them anywhere where through traffic has priority but other vehicles may be entering.

That's exactly how I'd like to see it used in the US. That's how it's used in British Columbia, even though it's actually a ped-activated crossing (as mentioned above) -- in every case I can think of, there is a cross street with a stop sign.

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Re: Traffic signal
« Reply #4769 on: September 15, 2022, 05:03:27 PM »

Yeah, this notion that flashing green should ever be replaced by flashing yellow is nonsense. Canada and Mexico allow flashing green and it's used in very clever and helpful ways. The FHWA, in my opinion, shoots itself in the foot by not allowing it. They would be wise to reconsider.

I think flashing green needs a definition in the US. I’d like to use them anywhere where through traffic has priority but other vehicles may be entering.

That's exactly how I'd like to see it used in the US. That's how it's used in British Columbia, even though it's actually a ped-activated crossing (as mentioned above) -- in every case I can think of, there is a cross street with a stop sign.
Exactly. Or even for a bicycle signal with a concurrent phase. Think of a leading bicycle interval:

Solid green for the head start, then flashing green when the conflict begins. Much better than the MUTCD approved flashing yellow bicycle.


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Re: Traffic signal
« Reply #4770 on: September 15, 2022, 05:42:53 PM »

Found a video posted 4 days ago about the more technical details of "smart" (for the lack of a better word) Dutch traffic lights, including their benefits and drawbacks, that some of you may be interested in.
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Re: Traffic signal
« Reply #4771 on: September 15, 2022, 08:25:16 PM »

The flashing green in the USA is strictly a Massachusetts thing as far as I know. My understanding is that it specifically indicates a pre-emption signal, one that's manually activated by a crosswalk push-button or a fire station signal, as compared to a signal that changes with regular phasing and/or vehicle demand.
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Re: Traffic signal
« Reply #4772 on: September 15, 2022, 08:54:28 PM »

4.  In Massachusetts, it isn't defined by law but is similar to (3) above, but could be found anywhere that may require extra caution—not just at crosswalks.

My understanding is that it specifically indicates a pre-emption signal, one that's manually activated by a crosswalk push-button or a fire station signal, as compared to a signal that changes with regular phasing and/or vehicle demand.

Hmm, I think you may be correct.  I can't actually identify one that isn't.
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Re: Traffic signal
« Reply #4773 on: September 15, 2022, 09:14:46 PM »

The one flashing green I remember in Braintree, Ma. was at a crosswalk/intersection at the entrance to Braintree High School. I believe it was converted to steady-green some years back.

And I should add, I actually like flashing green the way Massachusetts uses it, even it's not permitted by the MUTCD.
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Re: Traffic signal
« Reply #4774 on: September 15, 2022, 09:32:03 PM »

The flashing green in the USA is strictly a Massachusetts thing as far as I know. My understanding is that it specifically indicates a pre-emption signal, one that's manually activated by a crosswalk push-button or a fire station signal, as compared to a signal that changes with regular phasing and/or vehicle demand.
Arlington MA had a flashing green fire signal before 2013, so this seems accurate.

It’s not a flashing yellow. (Park avenue fire station if anyone is curious)


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