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Are these flasing yellow arrow sequences used anywhere?

Started by Revive 755, November 20, 2015, 10:49:11 PM

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Revive 755

Are either of these two sequences used anywhere with flashing yellow arrows:

* Green arrow -> steady yellow arrow -> flashing yellow arrow?  So far I've always seen a steady red arrow displayed before the FYA is brought up.

* For the through movements and corresponding left turn movements:  Green ball/flashing yellow arrow -> yellow ball/flashing yellow arrow -> red ball/flashing yellow arrow -> red ball/steady yellow arrow -> red ball/stead red arrow?  Some of the literature out there for signal equipment indicates that this sequence is allowed.


Katavia

I think in Concord (NC) there is an intersection not far from the RenFest (Annual Carolina Rennaisance Festival) (did I spell rennaisance right i mess up every time lol) that has a light that is

G
SY
FY
(Former) pizza delivery driver with a penchant for highways.
On nearly every other online platform I go by Kurzov - Katavia is a holdover from the past.

Ace10

Quote from: Revive 755 on November 20, 2015, 10:49:11 PM
Are either of these two sequences used anywhere with flashing yellow arrows:

* Green arrow -> steady yellow arrow -> flashing yellow arrow?  So far I've always seen a steady red arrow displayed before the FYA is brought up.

The City of Seattle has at least one traffic signal I've witnessed that goes green arrow > steady yellow arrow > flashing yellow arrow with no intermediary red arrow. All of the ones I've seen in Oregon always display a solid red arrow after the solid yellow arrow. All the ones in Oregon I've seen also do not show a flashing arrow at the exact same moment the through movement gets a green; there is always a delay of a few seconds where the red arrow is displayed before the flashing yellow arrow is.

jakeroot

Quote from: Ace10 on November 22, 2015, 08:14:26 PM
Quote from: Revive 755 on November 20, 2015, 10:49:11 PM
Are either of these two sequences used anywhere with flashing yellow arrows:

* Green arrow -> steady yellow arrow -> flashing yellow arrow?  So far I've always seen a steady red arrow displayed before the FYA is brought up.

The City of Seattle has at least one traffic signal I've witnessed that goes green arrow > steady yellow arrow > flashing yellow arrow with no intermediary red arrow. All of the ones I've seen in Oregon always display a solid red arrow after the solid yellow arrow. All the ones in Oregon I've seen also do not show a flashing arrow at the exact same moment the through movement gets a green; there is always a delay of a few seconds where the red arrow is displayed before the flashing yellow arrow is.

Makes a lot more sense to drop the red arrow. I have never understood the point to begin with. You should be able to continue going into the intersection, especially if there's no oncoming traffic. I shouldn't have to stop, then roll forward.

https://youtu.be/2QDiFJvYYas?list=PLvcdnO9vevXuhfwcmBt4plwx8hEN9nY8F

UCFKnights

Seemed tied to the red delay period between movements here. Some intersections have none or very short ones, and the solid yellow->red->FYA matches that. Some have a full several second delay between motions and the red is just as long for that. I guess that makes sense since they are always programmed flash yellow while opposing has green. If there is a delay before the opposing traffic has green, then that would not be true.

mrsman

Quote from: jakeroot on November 22, 2015, 09:36:26 PM
Quote from: Ace10 on November 22, 2015, 08:14:26 PM
Quote from: Revive 755 on November 20, 2015, 10:49:11 PM
Are either of these two sequences used anywhere with flashing yellow arrows:

* Green arrow -> steady yellow arrow -> flashing yellow arrow?  So far I've always seen a steady red arrow displayed before the FYA is brought up.

The City of Seattle has at least one traffic signal I've witnessed that goes green arrow > steady yellow arrow > flashing yellow arrow with no intermediary red arrow. All of the ones I've seen in Oregon always display a solid red arrow after the solid yellow arrow. All the ones in Oregon I've seen also do not show a flashing arrow at the exact same moment the through movement gets a green; there is always a delay of a few seconds where the red arrow is displayed before the flashing yellow arrow is.

Makes a lot more sense to drop the red arrow. I have never understood the point to begin with. You should be able to continue going into the intersection, especially if there's no oncoming traffic. I shouldn't have to stop, then roll forward.

https://youtu.be/2QDiFJvYYas?list=PLvcdnO9vevXuhfwcmBt4plwx8hEN9nY8F

IMO, as the signal displayed here is on the leading side, there should be a small 2 second dark phase between FYA and steady YA.  As mentioned above, you can still go if there is no opposing traffic, but the brief period of darkness* would help drivers recognize that the light did change from steady yellow arrow (meaning: protected turn just like green arrow that happens to be ending soon) vs. FYA (left turn permitted, yield to oncoming traffic).  If one does not recognize the difference, a left turner would gun the light thinking that it's about to end, without realizing that his protected turn actually already ended.

I do beleive that putting a red phase in there would be unnecessary though.

* In some ways during the brief dark phase, the signal operates like a doghouse signal, until the FYA is lit.

roadfro

Now that someone's mentioned it, I'll bet having that brief red between the steady yellow and transition to flashing yellow arrow is linked to whether or not a red time has been set for the phase.

The red time (possibly called an "all-red" in controller parlance, but doesn't really mean a red indication in all directions) adds a designated amount of time between the red being displayed for that phase before any conflicting phases get a green. If this phase doesn't have a red time, then it should go directly to FYA because the opposing through movement would start simultaneously.

Quote from: mrsman on November 25, 2015, 06:18:00 AM
IMO, as the signal displayed here is on the leading side, there should be a small 2 second dark phase between FYA and steady YA.  As mentioned above, you can still go if there is no opposing traffic, but the brief period of darkness* would help drivers recognize that the light did change from steady yellow arrow (meaning: protected turn just like green arrow that happens to be ending soon) vs. FYA (left turn permitted, yield to oncoming traffic).  If one does not recognize the difference, a left turner would gun the light thinking that it's about to end, without realizing that his protected turn actually already ended.

I do beleive that putting a red phase in there would be unnecessary though.

* In some ways during the brief dark phase, the signal operates like a doghouse signal, until the FYA is lit.

A brief dark phase wouldn't really be necessary. The visual jump in signal indication housing should be enough to make the distinction that the phase is different. The brief red actually helps in this regard, and helps the "gun the light" issue you mention by making it certain that the protected phase has ended. Much rather would have that than a couple seconds of vagueness caused by an intentionally dark signal.
Roadfro - AARoads Pacific Southwest moderator since 2010, Nevada roadgeek since 1983.

jakeroot

#7
Quote from: mrsman on November 25, 2015, 06:18:00 AM
If one does not recognize the difference, a left turner would gun the light thinking that it's about to end, without realizing that his protected turn actually already ended.

Even so, they're still permitted to go. They just have to yield. As far as I'm concerned, traffic still hasn't pulled off the line yet, so there still isn't any danger of proceeding even without a green arrow.

VARTV

Makes a lot more sense to drop the red arrow. I have never understood the point to begin with. You should be able to continue going into the intersection, especially if there's no oncoming traffic. I shouldn't have to stop, then roll forward.

https://youtu.be/2QDiFJvYYas?list=PLvcdnO9vevXuhfwcmBt4plwx8hEN9nY8F
[/quote]The City of Virginia Beach has just added these "protective red arrows" just recently.

US71

Quote from: Katavia on November 21, 2015, 08:06:47 AM
I think in Concord (NC) there is an intersection not far from the RenFest (Annual Carolina Rennaisance Festival) (did I spell rennaisance right i mess up every time lol) that has a light that is

G
SY
FY

Renaissance  ;)

I've seen a few intersections with

R
SY
FY
Like Alice I Try To Believe Three Impossible Things Before Breakfast

tradephoric

#10
The debate has shifted towards which is better... leading or lagging protected left-turns.

Leading lefts can be beneficial when you have uneven left-turn queues.  Suppose there are 20 vehicles queued up in the NBLT but only a couple vehicles in the SBLT.  With leading lefts you can allocate 40 seconds for the left turn phase and allow the SBLT to gap out early.   If the SBLT suddenly gets heavy, it can soak up the full 40 seconds if it needs it.  You couldn't do this with lagging lefts (you could set up the lagging lefts to start non-simultaneous and run the SBLT short, but then it wouldn't be able to service a sudden rush of SBLT traffic).

OTOH, it's annoying when a leading protected left runs when there is only one car in queue (a situation Jake described earlier in this thread).  To combat this, set the loops a few car lengths back from the stop bar or use video detection to determine how busy the left-turn movement is (this has also been discussed earlier in this thread).  If there are only a few cars turning left, the protected phase can skip and the signal functions as a simple two-phase traffic signal.  Put another way, only run the protected left turn phases when traffic demand warrants it.

jeffandnicole

Quote from: tradephoric on December 20, 2015, 11:53:12 AM
The debate has shifted towards which is better... leading or lagging protected left-turns.

Leading lefts can be beneficial when you have uneven left-turn queues.  Suppose there are 20 vehicles queued up in the NBLT but only a couple vehicles in the SBLT.  With leading lefts you can allocate 40 seconds for the left turn phase and allow the SBLT to gap out early.   If the SBLT suddenly gets heavy, it can soak up the full 40 seconds if it needs it.  You couldn’t do this with lagging lefts (you could set up the lagging lefts to start non-simultaneous and run the SBLT short, but then it wouldn’t be able to service a sudden rush of SBLT traffic).

OTOH, it’s annoying when a leading protected left runs when there is only one car in queue (a situation Jake described earlier in this thread).  To combat this, set the loops a few car lengths back from the stop bar or use video detection to determine how busy the left-turn movement is (this has also been discussed earlier in this thread).  If there are only a few cars turning left, the protected phase can skip and the signal functions as a simple two-phase traffic signal.  Put another way, only run the protected left turn phases when traffic demand warrants it.


The biggest issue with this is that some people expect the left turn arrow to turn every cycle.  So someone not paying full attention will see the green bulb lit...and assume they have the turn arrow and start to turn anyway.

tradephoric

He has a point Baloo.   You keep citing obscure traffic laws that are irrelevant to this discussion and proceed to misrepresent their intent.  You say things are exceptionally rare when they happens 11% of the time.   Your comments are adding more confusion than clarity to this thread.

UCFKnights

Quote from: jeffandnicole on December 20, 2015, 12:17:37 PM
Quote from: tradephoric on December 20, 2015, 11:53:12 AM
The debate has shifted towards which is better... leading or lagging protected left-turns.

Leading lefts can be beneficial when you have uneven left-turn queues.  Suppose there are 20 vehicles queued up in the NBLT but only a couple vehicles in the SBLT.  With leading lefts you can allocate 40 seconds for the left turn phase and allow the SBLT to gap out early.   If the SBLT suddenly gets heavy, it can soak up the full 40 seconds if it needs it.  You couldn't do this with lagging lefts (you could set up the lagging lefts to start non-simultaneous and run the SBLT short, but then it wouldn't be able to service a sudden rush of SBLT traffic).

OTOH, it's annoying when a leading protected left runs when there is only one car in queue (a situation Jake described earlier in this thread).  To combat this, set the loops a few car lengths back from the stop bar or use video detection to determine how busy the left-turn movement is (this has also been discussed earlier in this thread).  If there are only a few cars turning left, the protected phase can skip and the signal functions as a simple two-phase traffic signal.  Put another way, only run the protected left turn phases when traffic demand warrants it.


The biggest issue with this is that some people expect the left turn arrow to turn every cycle.  So someone not paying full attention will see the green bulb lit...and assume they have the turn arrow and start to turn anyway.
That hasn't been an issue here where there are plenty of examples like the one I posted.

Infact, for those who don't believe you're supposed to pull forward, lets take a look at why the FYA was created and why it is now replacing the doghouse/5 segment light everywhere...

The FYA was created to solve the problem of the "yellow trap" where drivers turning left pull into the intersection to prepare for a left turn to be made. The yellow trap occurs when either there is a lagging left (extremely rare, only 11% of the time), or it can also occur when there is no traffic on sidestreets and the signal is going to skip those phases and give the left turn arrow to one side of the street, but not the other or pre-emption of the signal.

If we weren't supposed to pull forward, "yellow trap" wouldn't be a thing, the FYA would have never been invented, and this whole topic wouldn't exist. We'd happily continue to use our doghouses.

jakeroot

Quote from: UCFKnights on December 20, 2015, 06:39:34 PM
The FYA was created to solve the problem of the "yellow trap" where drivers turning left pull into the intersection to prepare for a left turn to be made. The yellow trap occurs when either there is a lagging left (extremely rare, only 11% of the time), or it can also occur when there is no traffic on sidestreets and the signal is going to skip those phases and give the left turn arrow to one side of the street, but not the other or pre-emption of the signal.

If we weren't supposed to pull forward, "yellow trap" wouldn't be a thing, the FYA would have never been invented, and this whole topic wouldn't exist. We'd happily continue to use our doghouses.

That's a very good point, Knights. I know here in Washington, the FYA is being used simply because they allow for higher left turn AADT numbers, and are safer (WSDOT does not permit pro/per signals with lead/lag signals, so the yellow trap never existed here on WSDOT-maintained roads), but the FYA was indeed well touted for eliminating the yellow trap.

UCFKnights

Quote from: jakeroot on December 20, 2015, 08:17:37 PM
Quote from: UCFKnights on December 20, 2015, 06:39:34 PM
The FYA was created to solve the problem of the "yellow trap" where drivers turning left pull into the intersection to prepare for a left turn to be made. The yellow trap occurs when either there is a lagging left (extremely rare, only 11% of the time), or it can also occur when there is no traffic on sidestreets and the signal is going to skip those phases and give the left turn arrow to one side of the street, but not the other or pre-emption of the signal.

If we weren't supposed to pull forward, "yellow trap" wouldn't be a thing, the FYA would have never been invented, and this whole topic wouldn't exist. We'd happily continue to use our doghouses.

That's a very good point, Knights. I know here in Washington, the FYA is being used simply because they allow for higher left turn AADT numbers, and are safer (WSDOT does not permit pro/per signals with lead/lag signals, so the yellow trap never existed here on WSDOT-maintained roads), but the FYA was indeed well touted for eliminating the yellow trap.
Yellow trap would still exist in the event of pre-emption or if the side street and one left turn skipped a phase due to no activated detection, no? Or do the signals there always go to red and the side street for a few seconds even if there is no side traffic?

jakeroot

Quote from: UCFKnights on December 20, 2015, 09:03:02 PM
Yellow trap would still exist in the event of pre-emption or if the side street and one left turn skipped a phase due to no activated detection, no? Or do the signals there always go to red and the side street for a few seconds even if there is no side traffic?

Yes, in theory it would. Most of the signals in my area are activated via cameras, so if there is no side-street traffic and there is a line of cars waiting to turn left, (AFAIK) cameras check to make sure there aren't any cars in the oncoming left turn lane, and then flip on the green arrow. I have only seen this happen at night (when it's quiet).

Most of the time, however, you won't see another green arrow until the side street has had its phase. This is why I am mental about getting into the intersection to turn, because I know I won't get another green arrow until the side street gets to go. At busy junctions, this can be an additional 90 to 120 seconds of waiting, when I could have been able to turn when the light went red.

tradephoric

Can somebody explain to me, in very clear terms, a scenario where a yellow trap would occur at a flashing yellow arrow?

UCFKnights

Quote from: tradephoric on December 21, 2015, 08:05:05 AM
Can somebody explain to me, in very clear terms, a scenario where a yellow trap would occur at a flashing yellow arrow?
Only if the signal is programmed wrong. That is what the FYA was designed to solve and the reason it is replacing the 5 segment displays.

Ace10

^ From what I understand, the FYA is tied to the opposing through traffic's green (save for maybe the first few seconds where a solid red arrow is displayed before the FYA). As soon as the opposing through traffic's green turns yellow, the FYA changes to a solid yellow arrow, and that's the only time a solid yellow arrow is displayed after a FYA, so drivers facing the FYA when it turns solid yellow should know opposing through traffic is getting a red and it should be safe to clear the intersection if they are within it once opposing through traffic stops.

With a normal doghouse, it's impossible to show a permissive left indication while also showing a red light for through traffic facing the same direction. The FYA allows this. If a through indication goes red but a FYA continues to be displayed, the opposing through traffic is keeping their green, and left turners know to still yield to them. However, if the FYA goes solid yellow, left turners know their permissive phase is ending, but they also should infer that opposing through traffic is getting a red as well. You simply can't tell the two apart using a doghouse.

roadfro

#20
Quote from: tradephoric on December 21, 2015, 08:05:05 AM
Can somebody explain to me, in very clear terms, a scenario where a yellow trap would occur at a flashing yellow arrow?

The only scenario that makes any sense to me is in a preemption, but only if the controller is programmed to go red in all directions when preempted except for the direction of the approaching emergency vehicle.

Say the northbound left turn FYA is active, and a fire truck is heading southbound. As the preemption is initiated, the northbound FYA will cycle to red while the southbound through retains a green for the fire truck–Yellow trap results. (Again, this assumes the controller is programmed as stated above. I have not seen a preemption at an PPLT location with FYA, so have no idea if signal controllers are configured this way or not.)


Quote from: Ace10 on December 21, 2015, 02:43:36 PM
With a normal doghouse, it's impossible to show a permissive left indication while also showing a red light for through traffic facing the same direction. <...> You simply can't tell the two apart using a doghouse.

Well, it's not impossible... "Dallas Phasing" proved otherwise, through the use of a separate 5-aspect signal head for the left turn lane, louvers, and additional signal controller programming.

However, FYA is a better implementation.
Roadfro - AARoads Pacific Southwest moderator since 2010, Nevada roadgeek since 1983.

Ace10

Quote from: roadfro on December 22, 2015, 03:28:23 PM
Quote from: tradephoric on December 21, 2015, 08:05:05 AM
Can somebody explain to me, in very clear terms, a scenario where a yellow trap would occur at a flashing yellow arrow?

The only scenario that makes any sense to me is in a preemption, but only if the controller is programmed to go red in all directions when preempted except for the direction of the approaching emergency vehicle.

Say the northbound left turn FYA is active, and a fire truck is heading southbound. As the preemption is initiated, the northbound FYA will cycle to red while the southbound through retains a green for the fire truck—Yellow trap results. (Again, this assumes the controller is programmed as stated above. I have not seen a preemption at an PPLT location with FYA, so have no idea if signal controllers are configured this way or not.)

That's a scenario I hadn't thought of. Now that you mention it, there are a couple intersections I know of around here in Portland's western suburbs that have FYA signals preempted by nearby light rail tracks. Anytime a train approaches, the signals in the direction of traffic moving away from the railroad crossing turn green, but I don't know if the opposing direction's FYA turns red or not. In an emergency-vehicle-approaching situation, I would bet that the arrow would turn red, but for train pre-emption, I'd be less inclined to think it would turn red, though I have yet to actually catch the signal from that direction to see for sure. Luckily I live nearby such a signal, so I may go out and about to see how it operates as a train approaches and report back.

Quote from: roadfro on December 22, 2015, 03:28:23 PM

Quote from: Ace10 on December 21, 2015, 02:43:36 PM
With a normal doghouse, it's impossible to show a permissive left indication while also showing a red light for through traffic facing the same direction. <...> You simply can't tell the two apart using a doghouse.

Well, it's not impossible... "Dallas Phasing" proved otherwise, through the use of a separate 5-aspect signal head for the left turn lane, louvers, and additional signal controller programming.

However, FYA is a better implementation.

I guess I should have clarified, but for such a signal to be modified so it can support Dallas Phasing puts it out of the realm of 'normal' in my opinion. It wouldn't behave like any other doghouse would it not be for the louvers and other modifications. I fully agree with you though that the FYA is a better implementation.

jakeroot

The Seattle signal cited earlier in this thread has been modified. The old phasing (green arrow > solid yellow arrow > flashing yellow arrow > solid yellow arrow > solid red arrow) has been replaced by the more typical phasing, with the interim red between the protected and permissive phase.

Here's two clips. The first is the old phasing. The second is the new phasing. Apologies for the differing production quality. The second one I just uploaded straight from my phone. That's probably obvious, though.

https://youtu.be/dmoD0aX4wJM

https://youtu.be/OuB2E-QRLoE

doorknob60

In Nampa, I've seen some of the green arrow > solid yellow arrow > flashing yellow arrow > solid yellow arrow > solid red arrow phasing. One off the top of my head is 16th Ave and 3rd St. N. In Ada County, I don't think there are any, as ACHD has a policy to have a (5 second?) red phase between green arrow and FYA. And if I'm not mistaken, ACHD controls every traffic signal in the county, including on ITD maintained roads.



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