My humble criticism of the FYA: an unintentional ambiguity created

[MisterSG1]

I briefly discussed this with cl94 while we are on the road during the GTA roadmeet today. But there are many reasons why I think the FYA is an overall bad idea....while there are a few pros involved, I think the cons outweigh the pros here and let me explain why.

As we know, the FYA eliminates the issue of yellow trap scenarios, but that's a moot point here anyway, as creating any phasing that causes a yellow trap situation is illegal in Ontario.

Let's be brutally honest, the yellow trap only becomes an issue if you choose to use these phases for signals. The lagging permissive-protected left turn and the leading-lagging permissive-protected left turn. Personally, I don't see the first option really having any practicality and being better than a leading permissive-protected left turn. If someone can bring forth a strong argument on why lagging left has a stronger advantage over leading left, I'd like to hear it. As for leading-lagging left, I could see a possible benefit if one particular direction has a stronger demand in traffic proceeding straight, but what can be accomplished here in this case could easily be accomplished with a leading simultaneous left turn in which one of the sides ends early, effectively making one direction get a preemptive jump on the light.


Another thing I hear as a positive is that a FYA light allows the phasing to change from fully protected to permissive-protective.

While indeed this is a positive, I guess it depends on where you live, but in MOST intersections here in the GTA and Ontario, fully protected lefts are put on situations in which there are 2 left turning lanes. BUT, there is NOWHERE in Ontario where 2 left turn lanes get a PPLT. I can understand issues with line of sight from the outer left turn lane being a factor as to why they never allow it. As for single lane fully protected left turns, is there a serious reason why this kind of light should ever exist? Other than if the intention is to give it lagging left phasing, this is the only reason why a single left turning lane should ever get a fully protect left turn. I understand that this kind of phasing occurs on Lake Shore Blvd and Ellis Ave if I recall. In this case, a FYA is an improvement, I will admit.


I've also heard at one point that FYA is introduced because drivers don't understand what "LEFT TURN YIELD ON GREEN" means. No offense, but if you don't know the basics in that you should make a left turn only if it is safe to do so with no oncoming traffic, you shouldn't be driving in the first place! But hold that thought for a second as I combine it with my next point below.

In another thread where I discussed ambiguity regarding the flashing red signal, I suggested that a new red/yellow flashing signal be introduced, and cbeach40 responded with an excellent point, the cost to implement something like that would be VERY expensive. Now consider, if every state is to replace their traditional arrow PPLT signals, call them doghouses, or 5 heads, or 4 heads (which they use here) that alone would cost BILLIONS.

Now back to my previous point about yielding on green, if drivers now need this new flashing yellow arrow signal to tell them that they can only turn if safe to do so, you then get to the point where not only PPLT signals need to be replaced, but EVERY SINGLE traffic light out there, the ones that don't have anything special for left turns, would have to be reconfigured to have a special signal for going straight/right and a special signal for turning left. This leads to consistency across the board, I imagine such a signal being a 3 head with from top to the bottom, red arrow, solid yellow arrow, flashing yellow arrow. Thus you eliminate "LEFT TURN YIELD ON GREEN" altogether.


Now to my main criticism that started all of this

Even if you ignore all the points above, one thing that is very important when designing any kind of traffic control is not allowing any ambiguity to happen. If such a device can have two meanings, it's purpose is lost. Unfortunately I hate to say this, but for the most part, drivers are indeed idiots, and we do have to dumb things down and make it as simple as possible.

To cut to the main point, the flashing yellow arrow signal is not the ambiguity, but inadvertently, they have created an ambiguity with the SOLID yellow arrow.

Let me explain, if a FYA signal is given a leading left sequence, pay attention to this sequence, I will writeit down below, the sequence of the left arrow and the main light:

LEFT SIGNAL                 MAIN SIGNAL

Red Arrow                     Red Ball
Green Arrow                  Red Ball
SOLID Yellow Arrow        Red Ball
Red Arrow                     Red Ball
FLASHING Yellow Arrow  Green Ball
SOLID Yellow Arrow        Yellow Ball
Red Arrow                     Red Ball

When the solid yellow arrow appears during the protected phase, it means the same thing as we always know it to mean, the right of way on the left turn is ending. However, when the solid yellow arrow appears during the second phase, in which the main light is now a yellow ball, we have a situation where a solid yellow arrow appears in which that movement DOES NOT have the right of way. This alone is why I am very critical of the FYA sequencing. Sure, one should see that the yellow arrow is blinking, but let's be honest for a second, it is ingrained in our minds that a yellow arrow means MAKE THAT LEFT TURN RIGHT NOW. This alone also ELIMINATES the case in that arrow signals ALWAYS signify that the specific movement shown by the arrow signal has right of way.

One such solution I propose is to use a 5 signal head, and instead of the flashing yellow arrow, use a flashing yellow ball (of course make it clear that this light is for left movements only) and instead of the solid yellow arrow in the regular phase, use a yellow ball. This eliminates the newly created ambiguity.

So anyways folks, this is my rant about this.

[opspe]

In Oregon, where the FYA is very very common and has been for a decade or so, the phasing goes something more like this:

LEFT SIGNAL                 MAIN SIGNAL

Red Arrow                     Red Ball        <Begin protected turn phase>
Green Arrow                  Red Ball
SOLID Yellow Arrow        Red Ball
Red Arrow                     Red Ball        <End protected turn phase>
Red Arrow                     Green Ball     <Begin thru phase>
FLASHING Yellow Arrow  Green Ball     <Begin permissive turn phase>
SOLID Yellow Arrow        Green Ball
Red Arrow                     Yellow Ball     <End permissive turn phase>
Red Arrow                     Red Ball        <End thru phase>

The permissive turn phase starts after and ends before the thru traffic (normal) phase.  This has two effects.

First, thru traffic is given a brief period where they can be sure there are no left turns happening.  This serves to clear out thru traffic backed up at the intersection, so that left turns in the permissive phase won't get stalled.

Second, by ending the permissive turn phase before the thru phase, this eliminates (or at least minimizes) your primary concern over the "gun it" mentality when turning.

Also, there seems to be a mix of FYA signals used in Oregon, one with three heads (flashing yellow and solid green arrows are shared on the bottom head) and one with four (solid yellow arrow above flashing yellow arrow).  In both cases, the solid and flashing yellow arrows are displayed on separate heads.

(edit: whoops, posted too early)

[MisterSG1]

Ok, what I actually described was a simultaneous leading left...but whatever we will stick with this example. I was just pointing out my mistake.

Anyways, even if the main light remains green in the permissive phase while the left gets a solid yellow, this does not mean that the solid yellow arrow avoids the pitfall I'm talking about.

By the rule book we all know what a solid yellow arrow is supposed to mean, complete the turn if in the intersection and do not start the turn if you are not in the intersection.

Fair enough, but in reality, usually one or two vehicles finds a way to squeeze by even when a solid yellow arrow appears, this doesn't pose much of a problem in the pre FYA PPLT signals. However during the permissive phase, the solid yellow arrow appears while the left is not protected, this means that a driver deciding to gun it can create a nasty collision with oncoming vehicle. Remember what I said, most drivers are idiots.

[jakeroot]

Second, by ending the permissive turn phase before the thru phase, this eliminates (or at least minimizes) your primary concern over the "gun it" mentality when turning.

Are you absolutely certain that this is the case? You're describing a variation of the yellow trap. FYA's and through signals need to be tied together. If the FYA goes red before the through traffic, any traffic waiting in the junction to turn left will start to go, even though oncoming traffic doesn't have a red.

[MisterSG1]

Second, by ending the permissive turn phase before the thru phase, this eliminates (or at least minimizes) your primary concern over the "gun it" mentality when turning.

Are you absolutely certain that this is the case? You're describing a variation of the yellow trap. FYA's and through signals need to be tied together. If the FYA goes red before the through traffic, any traffic waiting in the junction to turn left will start to go, even though oncoming traffic doesn't have a red.

Not a variation of a yellow trap situation, IT IS a yellow trap situation. Good catch.

[Jet380]

So the ambiguity is the solid yellow arrow means two different things, depending on what directly preceded it? Either 'make protected left turn if unable to stop safely' if following a green arrow or 'make left turn to clear intersection when safe' following a FYA.

I would argue that in most cases the context of what light was showing before the change to solid yellow is enough for drivers to understand what to do. If you see only the solid yellow come on without noticing what came before it, then it's probably because the intersection just came into view and the light will be red by the time you get to it anyway.

But to account for people who maybe aren't paying attention to the signal before it changes, one alternative might be to have a dual-mode solid yellow signal, that can either show a ball or an arrow depending on the phase it is terminating. So you get either

Green arrow -- yellow arrow -- red arrow
or
Flashing yellow arrow -- yellow ball -- red arrow

This would also help people to react faster to the end of the permissive phase, especially at night as the signal changes shape instead of just stopping flashing.

FWIW my jurisdiction has ruled out the use of FYAs on the basis that they feel drivers will consider any arrow indication other than red to be an invitation to turn without yielding - which isn't what has been seen elsewhere but anyway. They are completely happy to leave yellow traps in place at railroad-preempted intersections though. 

[jakeroot]

You bring up a very good point, MisterSG1. Granted, I'm not totally certain that this is really that big of an issue. But, it's an interesting point nonetheless.

Washington's RCW (the lawbook) defines a solid yellow indication as follows:

(2) Steady yellow indication
(a) Vehicle operators facing a steady circular yellow or yellow arrow signal are thereby warned that the related green movement is being terminated or that a red indication will be exhibited immediately thereafter when vehicular traffic shall not enter the intersection...

My interpretation here is that a solid yellow means two different things, depending on whether or not it was preceded by a green arrow, or something else.

Your assumption is that drivers will see a yellow arrow, automatically assume it was preceded by a green arrow, and gun it straight into oncoming traffic. I know drivers aren't brilliant, but that's a whole other level of stupidity. I mean, it's not beyond some drivers, for sure, but I don't think it's something that occurs often.

The prime advantages of the FYA, AFAIC, are the ability to create TOD phasing, mix leading and lagging protected turns, as well as permit leading pedestrian intervals (allowing peds to start crossing before the FYA comes on). None of these things are really possible with 4/5-section towers. While there is some ambiguity as to what the solid yellow arrow means, I don't think it's as big of a deal when you consider the upsides of FYAs.

FWIW, to the best of my knowledge, fully protected single-lane left turns are generally used only when it's insanely busy, to prevent people from splitting gaps in oncoming traffic that would ordinarily be too small, but become huge when there road is handling more cars than usual.

[jakeroot]

FWIW my jurisdiction has ruled out the use of FYAs on the basis that they feel drivers will consider any arrow indication other than red to be an invitation to turn without yielding - which isn't what has been seen elsewhere but anyway.

Is there any official documentation on that? It's not that I don't believe you (I do), but I had no idea that Australia had considered the FYA as a right turn signal.

Second, by ending the permissive turn phase before the thru phase, this eliminates (or at least minimizes) your primary concern over the "gun it" mentality when turning.

Are you absolutely certain that this is the case? You're describing a variation of the yellow trap. FYA's and through signals need to be tied together. If the FYA goes red before the through traffic, any traffic waiting in the junction to turn left will start to go, even though oncoming traffic doesn't have a red.

Not a variation of a yellow trap situation, IT IS a yellow trap situation. Good catch.

I only said variation because, when the red arrow is displayed, oncoming traffic has a yellow signal instead of a green. Still a trap, but it's only for three or four seconds, versus however long an opposing lagging protected turn might last.

[opspe]

I guess I'm more used to the Vancouver-style yellow trap, i.e. where cars are stuck in an intersection trying to turn left literally until the cross traffic gets a green, and often times after.  People (including 60' articulated buses) routinely run left turns on red, tailing all the cars piled up in the yellow trap.  So for here, FYA would be a big improvement.

[jakeroot]

I guess I'm more used to the Vancouver-style yellow trap, i.e. where cars are stuck in an intersection trying to turn left literally until the cross traffic gets a green, and often times after.  People (including 60' articulated buses) routinely run left turns on red, tailing all the cars piled up in the yellow trap.  So for here, FYA would be a big improvement.

Washington or BC? BC is crazy about piling as many cars into the junction as possible during the permissive phase, behavior that I don't witness as often here in Washington.

[opspe]

I guess I'm more used to the Vancouver-style yellow trap, i.e. where cars are stuck in an intersection trying to turn left literally until the cross traffic gets a green, and often times after.  People (including 60' articulated buses) routinely run left turns on red, tailing all the cars piled up in the yellow trap.  So for here, FYA would be a big improvement.

Washington or BC? BC is crazy about piling as many cars into the junction as possible during the permissive phase, behavior that I don't witness as often here in Washington.

BC.  The only proper protected left turn signals in this city are in provincially maintained intersections, which basically just means at freeway offramps.  Of which there are a grand total of two.

[jakeroot]

I guess I'm more used to the Vancouver-style yellow trap, i.e. where cars are stuck in an intersection trying to turn left literally until the cross traffic gets a green, and often times after.  People (including 60' articulated buses) routinely run left turns on red, tailing all the cars piled up in the yellow trap.  So for here, FYA would be a big improvement.

Washington or BC? BC is crazy about piling as many cars into the junction as possible during the permissive phase, behavior that I don't witness as often here in Washington.

BC.  The only proper protected left turn signals in this city are in provincially maintained intersections, which basically just means at freeway offramps.  Of which there are a grand total of two.

I was confused about where you were located. Your location indicates the US, your avatar says Oregon, but your posts say BC. Anyways, yeah, within the city, there are very few protected turns. The first location I thought of was the left turn onto Hwy 1 SB from E 1 Ave (MOT maintained, as you indicate).

We ought to have a meetup one day. I'm in Vancouver all the time. I'll message you sometime in the future, to avoid getting too off-topic here.

[Jet380]

Is there any official documentation on that? It's not that I don't believe you (I do), but I had no idea that Australia had considered the FYA as a right turn signal.

It's nothing officially documented or anything, but this is from a response to an enquiry I sent a while ago:

The Road Traffic Code currently informs drivers that if they have a green arrow then they have right of way over pedestrians if they are turning. The Australian Road Rules have the option of a flashing yellow arrow but the similarities with the green arrow may contribute to confusion about who has to give way and when. Arrow signals are used throughout Western Australia but with red and green aspects rather than a flashing yellow.

[tradephoric]

If someone can bring forth a strong argument on why lagging left has a stronger advantage over leading left, I'd like to hear it.

Simple answer is coordination.  There are plenty of examples where you would get better coordination with lagging left turns as opposed to leading.  Imagine a FYA T-intersection that is 1000 feet from the main.  With lagging lefts you get the entire platoon through the intersection but with leading you cut off a lot of traffic. 

[johndoe]

This site is very thorough, you may enjoy it: http://midimagic.sgc-hosting.com/fyatruth.htm

There are many relevant pages there.

[MisterSG1]

This site is very thorough, you may enjoy it: http://midimagic.sgc-hosting.com/fyatruth.htm

There are many relevant pages there.

Look, I know exactly what the yellow trap is, that is not the issue. What a solid yellow arrow means in the rulebook, and what it means in reality are two separate things. My concern is a driver upon seeing a solid yellow and not paying attention to the status of the light for traffic going straight, is immediately thinking to himself, "Make that left turn and don't think", before the introduction of FYA a SYA indeed meant that ALL THE TIME, the introduction of FYA changes the meaning the of SYA.

Where I live, such single lag left or lead-lag left is never used here at all because of the issues regarding yellow trap. I'm being economical about the whole thing, is it worth it spending an astronomical amount of money to add the new signals just so we can introduce these phases which show if anything, little added benefit?

And I challenge you, those who say that the FYA allows switching between PPLT and FPLT modes....while yes it would allow the left turn mode to indeed be amphibious, the question I ask, is there anywhere that actually switches between PPLT and FPLT at different points of the day?


As for the person who mentioned TOD, I'd have to do more research on how it works in different places. Around here, streetcars/buses which have a dedicated right of way have a RYG signal that is timed precisely with the main traffic for proceeding straight. I know it's a bit off topic, but it's traffic signal phasing that is my main pet peeve and my main reason as to why I am strongly opposed to the LRT projects in Toronto that use ROW.


FYA will probably never be used in Ontario in my opinion, when you consider that yellow and red arrow signals for fully protected movements currently by law have to use ball signals, only the green gets the arrow signal. A lot of legislation would have to be changed to allow these new signals.

[hotdogPi]

And I challenge you, those who say that the FYA allows switching between PPLT and FPLT modes....while yes it would allow the left turn mode to indeed be amphibious, the question I ask, is there anywhere that actually switches between PPLT and FPLT at different points of the day?

Before the left turn mode can be amphibious, we need cars that can drive on water.

[MisterSG1]

And I challenge you, those who say that the FYA allows switching between PPLT and FPLT modes....while yes it would allow the left turn mode to indeed be amphibious, the question I ask, is there anywhere that actually switches between PPLT and FPLT at different points of the day?

Before the left turn mode can be amphibious, we need cars that can drive on water.

Maybe hybrid was a better word to use, but I meant amphibious as in a dual quality:

But on dictionary.com, it indeed says this using the meaning I intended:

"combining two qualities, kinds, traits, etc.; of or having a mixed or twofold nature. "

[Brandon]

I would have to say that my preference is for lagging over leading protective/permissive lefts.  The reason being is that leading lefts left to lead to a bunch of people stuck in the intersection when the signal turns red.  Cross traffic then has to wait for them to complete their left turns before proceeding.  Lagging lefts allow the permissive part first, letting that traffic take gaps in traffic, and waiting for the protective phase if there are no gaps.  It then allows the left turn lane to clear on the protective phase after the through signal has turned red.  It also means that no one is stuck in the intersection after the signal has turned red, and through traffic can start up on green much faster.

[MisterSG1]

I would have to say that my preference is for lagging over leading protective/permissive lefts.  The reason being is that leading lefts left to lead to a bunch of people stuck in the intersection when the signal turns red.  Cross traffic then has to wait for them to complete their left turns before proceeding.  Lagging lefts allow the permissive part first, letting that traffic take gaps in traffic, and waiting for the protective phase if there are no gaps.  It then allows the left turn lane to clear on the protective phase after the through signal has turned red.  It also means that no one is stuck in the intersection after the signal has turned red, and through traffic can start up on green much faster.

Yes I agree with you, mainly when that is used in the case of a simultaneous lagging left, which DOES NOT cause a yellow trap situation to occur. As far as I know, even that kind of phasing is never seen here and there are places where I think it should be used. There are some lagging lefts involving fully protected turns though I know on Lake Shore Blvd in downtown Toronto.

The issue as to why a FYA is needed is to allow a lagging single left (or shall I say, a lagging advanced green) to prevent the yellow trap from occurring. Is it worth the money as well to change the nature of arrow signals to allow this phase? I'm not entirely convinced a lagging advanced green phase is inherently more superior than a leading advanced green phase.

[jakeroot]

And I challenge you, those who say that the FYA allows switching between PPLT and FPLT modes....while yes it would allow the left turn mode to indeed be amphibious, the question I ask, is there anywhere that actually switches between PPLT and FPLT at different points of the day?

Federal Way, Washington. Many of the FYAs along Hwy 99, the main artery through the city, go protected-only during rush hour.

This is a quote from Rick Perez, the city'e traffic engineer, on how they use the FYA:

My basic philosophy is the best left‐turn phase is a skipped left‐turn phase.  Waiting for "green for [g]hosts" is a pet peeve of mine, so I avoid protected lefts like the plague.

Here is our current formal policy language:

"Left‐turn phasing shall be the least restrictive possible:
1. Default to permitted.
2. Protected/Permitted if needed for capacity.  If exclusive left‐turn lanes are provided, flashing yellow arrow displays shall be used.
3. Protected if sight distance inadequate (based on AASHTO intersection sight distance criteria for left‐turns into minor approach ‐ Case F), high pedestrian volumes, high conflicts or accident experience, more than one left‐turn lane, or for lead/lag operation."

Current practice is evolving to flashing yellow arrow everywhere there is a dedicated left‐turn lane, and then make the decision about how to run it.  One advantage of installing FYA where permitted would otherwise work just fine is in pre‐emption, but I also like having the flexibility to address transient peaks in left‐turn volumes due to detours or incidents.  I also have a location that we will eventually put in FYA even though it's a dual left, and there may be more, even against 3 or 4 opposing lanes, at least by time‐of‐day.  I will run a FYA approach in protected only mode by TOD if there are no gaps available.

As for sequence, if the corridor is coordinated, I'll run whatever gives me the best greenbands.  I try to lag heavier movements.  If the approach isn't coordinated, I lead most protected lefts (but I lag them if they are particularly heavy), and lag all FYA approaches and have the left‐turn detection extend the opposing through movements to maximize the opportunity for the left turn to move without calling up the left‐turn phase.

We use 5 left‐turn collisions per approach per year as the threshold to go to Protected Only phasing.  Other than that and sight distance, I'm really leaning towards LADOT's use of gap availability by TOD.

Here's a link to the PDF with the response, along with several others from other traffic engineers: http://goo.gl/h5yuQJ

[johndoe]

SG1, I'm not saying you don't understand, I was referring to the "other methods " on this page: http://midimagic.sgc-hosting.com/leadlag.htm

[vdeane]

I would have to say that my preference is for lagging over leading protective/permissive lefts.  The reason being is that leading lefts left to lead to a bunch of people stuck in the intersection when the signal turns red.  Cross traffic then has to wait for them to complete their left turns before proceeding.  Lagging lefts allow the permissive part first, letting that traffic take gaps in traffic, and waiting for the protective phase if there are no gaps.  It then allows the left turn lane to clear on the protective phase after the through signal has turned red.  It also means that no one is stuck in the intersection after the signal has turned red, and through traffic can start up on green much faster.

In New York, only the first car and go past the stop line into the intersection.  If they can't get through, the all-red phase should allow them to get out, assuming that oncoming traffic doesn't violate the red.

[mariethefoxy]

On Long Island, the only places you see the Green with Green Arrow after the Green phase is when its a sideways T intersection (the cross street its a T) rather than a + intersection. If its a + the green arrow comes on when the main is red, then goes Red with Yellow Arrow then Red again briefly then Green or then to Green with Left Green Arrow if theres a lot of people turning.

[Brandon]

I would have to say that my preference is for lagging over leading protective/permissive lefts.  The reason being is that leading lefts left to lead to a bunch of people stuck in the intersection when the signal turns red.  Cross traffic then has to wait for them to complete their left turns before proceeding.  Lagging lefts allow the permissive part first, letting that traffic take gaps in traffic, and waiting for the protective phase if there are no gaps.  It then allows the left turn lane to clear on the protective phase after the through signal has turned red.  It also means that no one is stuck in the intersection after the signal has turned red, and through traffic can start up on green much faster.

In New York, only the first car and go past the stop line into the intersection.  If they can't get through, the all-red phase should allow them to get out, assuming that oncoming traffic doesn't violate the red.

In Illinois, as long as your front wheels are past the stop line on yellow, you can continue through the intersection.  Hence, we can have a whole conga line of vehicles in the intersection when it turns red.  I've seen as many as three in the intersection waiting, and another one or two typically follow anyway.