My humble criticism of the FYA: an unintentional ambiguity created

[jakeroot]

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.

It's so funny how much this behavior differs between cities. Here in Seattle, you might have one car pull past the stop line, but that's usually it. But up and British Columbia, it's much like Illinois. As long as those front tires are past the stop line, you better get moving. Some longer intersections can pack as many as five cars in the box.

As you might imagine, I much prefer driving in British Columbia than here in Washington.

[Revive 755]

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!

You left out the case where the driver is expecting a green arrow, possibly at the same time with a green ball, and the arrow fails to come up.  The FYA provides a much clearer, distinctive indication for left turns and is very helpful for those traveling in areas that use left turn phasing different from what they are used to, or for signals that do not provide protected left turns for parts of the day.

You do not cite the advantage of the FYA in being able to allow left turners to turn permissive while the adjacent through lane still has a red indication - very helpful for side streets where it is possible to arrive one second too late and have to wait for the next cycle for the chance to turn.

Nor do I see mention of the case where the left turn is across a railroad track, and use of a FYA head provides a better indication that left turns are not allowed at the time - certainly more so than having a 5-section head with one or more blank-out signs.

While the FYA is a significant improvement over the older 5-section designs, the older signals still work well enough in most cases that FYA heads can be added as the signals need to be upgraded or rebuilt for other reasons.

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.

Observing the first FYA installations in a region without them indicates this is not the case.  Also, yellow balls still have issues with left turners feeling the urgent need to suddenly make their turn, and then getting creamed by an opposing driver who is trying to make it through the intersection before getting a red light.

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.

In places where I've heard the 'arrow means go' argument against installing red arrows, there does not seem to be issues with blatant violations of the red arrows after they were installed.

Sure the FYA creates two new ambiguities - the steady yellow arrow as well as flashing yellow meaning 'yield' or 'caution' depending upon the case, but it opens up enough opportunities to be worth those two ambiguities.

[roadfro]

I think this is the first thread where someone's issue with the FYA comes from the solid yellow arrow...

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.

Ontario Ministry of Transportation, Driver's Handbook

A yellow – or amber – light means the red light is about to appear. You must stop if you can do so safely; otherwise, go with caution.

A little bit different definitions. But the handbook makes the distinction. A solid yellow does not automatically equate to "go", despite what common practice has developed.

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?

There are multiple signals in the Las Vegas, NV area using FYA displays that switch into protected only mode during peak hour times. Las Vegas uses a lot of coordination on its arterials, so many left turns are run lead-lag to improve coordination. Simultaneously, platoons of opposing through vehicles on these arterials are typically heavy with little-to-no gaps to allow a permitted turn safely. (Many such situations are on arterials with three through lanes and speeds of 45mph or greater, which increases likelihood of no gap in peak travel times.) The protected mode only operates during peak periods, so permitted turning movements are allowed in off-peak times when it is more likely for there to be more gaps in opposing traffic.

At some signals, prior to installation of FYAs, the same effect was achieved with "Dallas Phasing" in a 5-aspect signal head (doghouse/vertical stack). This required a separate signal head anyway, with louvers on the green and yellow balls to allow permitted indications when the adjacent through vehicles had a red--I believe this also required extra signal controller programming to make it work. The FYA display achieves the same purpose, with a 4-aspect head and no additional programming required.

[Mergingtraffic]

I'm not a big fan of the FYA either.

Whenever you have an arrow (unless it's red) it means you have the right of way to make your turn.
SO, whenever a YELLOW ARROW is up it means your right of way is ending...but you STILL have the right of way.  But, with a flashing yellow arrow it means you do NOT have the right of way. 

I know there are signs that go along with the FYA, but the meaning shouldn't be so "complicated" you need a sign to explain it more.

[Revive 755]

Whenever you have an arrow (unless it's red) it means you have the right of way to make your turn.
SO, whenever a YELLOW ARROW is up it means your right of way is ending...but you STILL have the right of way.  But, with a flashing yellow arrow it means you do NOT have the right of way. 

I know there are signs that go along with the FYA, but the meaning shouldn't be so "complicated" you need a sign to explain it more.

And this is different than the dual meanings you can get with a circular green? With a circular green (assuming no pedestrian crossings), you have the right of way if going straight or turning right, but not if you are turning left.

[roadfro]

I'm not a big fan of the FYA either.

Whenever you have an arrow (unless it's red) it means you have the right of way to make your turn.
SO, whenever a YELLOW ARROW is up it means your right of way is ending...but you STILL have the right of way.  But, with a flashing yellow arrow it means you do NOT have the right of way. 

I know there are signs that go along with the FYA, but the meaning shouldn't be so "complicated" you need a sign to explain it more.

Not quite... Meanings below paraphrased from 2009 MUTCD, Section 4D.04:


Green arrow = Driver may enter the intersection to make the movement indicated by the arrow

Flashing Yellow arrow = Driver may enter the intersection to make the movement indicated by the arrow, and must yield to pedestrians or other vehicles lawfully in the intersection (and for turns to the left, must also yield to oncoming traffic)

Steady yellow arrow = Driver is warned that the associated green arrow or flashing yellow arrow movement is terminating. The rules governing vehicle movements on the phase being terminated remain active during the steady yellow arrow.

[MisterSG1]

I'm not a big fan of the FYA either.

Whenever you have an arrow (unless it's red) it means you have the right of way to make your turn.
SO, whenever a YELLOW ARROW is up it means your right of way is ending...but you STILL have the right of way.  But, with a flashing yellow arrow it means you do NOT have the right of way. 

I know there are signs that go along with the FYA, but the meaning shouldn't be so "complicated" you need a sign to explain it more.

Bingo, that's the point I'm getting at, but one slight correction. With a solid yellow arrow when FYA exists, it means you DON'T NECESSARILY have the right of way. Before the introduction of FYA, a solid yellow always meant that a driver still has the right of way.

I do have a solution that could have done all of this and wouldn't require the retweaking of rules, I of course would need to find out how you make an animated gif to do it. To make a sequence similar to the ones shown on the link on this thread.


Just a question, when a FYA intersection uses a leading left, or leading simultaneous left sequence, does the left arrow always go back to the red arrow before the flashing yellow arrow appears? Normally in the 4/5 head signal, or doghouse, depending on how its oriented in your area, there generally isn't a dead pause of turning traffic, which I think is a great idea personally that's easy to accomplish with a FYA.

[roadfro]

Just a question, when a FYA intersection uses a leading left, or leading simultaneous left sequence, does the left arrow always go back to the red arrow before the flashing yellow arrow appears? Normally in the 4/5 head signal, or doghouse, depending on how its oriented in your area, there generally isn't a dead pause of turning traffic, which I think is a great idea personally that's easy to accomplish with a FYA.

I think we've established that many jurisdictions do have the red arrow display in transitioning from protected to permitted (Nevada does, even if it is as brief as one second or less), but also that some jurisdictions omit the red arrow. According to the MUTCD, the red arrow is not required to display in this transition.

[Henry]

I have a bad feeling that the FYA will eventually supersede the doghouse signal, which thankfully is trying to hang on for as long as possible. FWIW, I prefer the doghouse because it gives a better idea when you can and can't turn left. For comparison purposes, these are the phases of a FYA and doghouse (LTA=Left Turn Arrow):

DOGHOUSE
Green LTA/Red ball
Yellow LTA/Red ball
No LTA/Green ball
No LTA/Yellow ball
No LTA/Red ball

ALTERNATE DOGHOUSE
Green LTA/Green ball
Yellow LTA/Green ball
No LTA/Green ball
No LTA/Yellow ball
No LTA/Red ball

ALTERNATE DOGHOUSE 2
Green LTA/Green ball
Yellow LTA/Yellow ball
No LTA/Red ball

FYA
Green LTA/Red ball
Steady yellow LTA/Red ball
Flashing yellow LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

ALTERNATE FYA
Green LTA/Green ball
Flashing yellow LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

ALTERNATE FYA 2
Green LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

[hotdogPi]

I have a bad feeling that the FYA will eventually supersede the doghouse signal, which thankfully is trying to hang on for as long as possible. FWIW, I prefer the doghouse because it gives a better idea when you can and can't turn left. For comparison purposes, these are the phases of a FYA and doghouse (LTA=Left Turn Arrow):

DOGHOUSE
Green LTA/Red ball
Yellow LTA/Red ball
No LTA/Green ball
No LTA/Yellow ball
No LTA/Red ball

ALTERNATE DOGHOUSE
Green LTA/Green ball
Yellow LTA/Green ball
No LTA/Green ball
No LTA/Yellow ball
No LTA/Red ball

ALTERNATE DOGHOUSE 2
Green LTA/Green ball
Yellow LTA/Yellow ball
No LTA/Red ball

FYA
Green LTA/Red ball
Steady yellow LTA/Red ball
Flashing yellow LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

ALTERNATE FYA
Green LTA/Green ball
Flashing yellow LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

ALTERNATE FYA 2
Green LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

You're missing the new possibility of "Flashing yellow LTA/Red ball", which is not possible with a doghouse signal.

[tradephoric]

How many agencies suppress the flashing yellow arrow when the adjacent through is displaying a red?  This is common around here.  So if leading lefts terminate non-simultaneous, you will see an extended solid red arrow until the adjacent through turns green.  This setup really doesn't affect capacity since at the start of the opposing through traffic will likely be queued up preventing any permissive turns from being made anyways.

EDIT:  This type of setup is only meant for leading lefts.  Obviously, with lagging lefts you may need the flashing yellow arrow to be on when the adjacent through is red to prevent the yellow trap.

[MisterSG1]

I have a bad feeling that the FYA will eventually supersede the doghouse signal, which thankfully is trying to hang on for as long as possible. FWIW, I prefer the doghouse because it gives a better idea when you can and can't turn left. For comparison purposes, these are the phases of a FYA and doghouse (LTA=Left Turn Arrow):

DOGHOUSE
Green LTA/Red ball
Yellow LTA/Red ball
No LTA/Green ball
No LTA/Yellow ball
No LTA/Red ball

ALTERNATE DOGHOUSE
Green LTA/Green ball
Yellow LTA/Green ball
No LTA/Green ball
No LTA/Yellow ball
No LTA/Red ball

ALTERNATE DOGHOUSE 2
Green LTA/Green ball
Yellow LTA/Yellow ball
No LTA/Red ball

FYA
Green LTA/Red ball
Steady yellow LTA/Red ball
Flashing yellow LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

ALTERNATE FYA
Green LTA/Green ball
Flashing yellow LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

ALTERNATE FYA 2
Green LTA/Green ball
Steady yellow LTA/Yellow ball
Red LTA/Red ball

Ok, the first example under "Doghouse" you gave is what we sometimes call a "leading-leading left" that is both sides get a protected left arrow while traffic for proceeding straight on either side faces a red ball. In Ontario this is known as a "simultaneous left turn" and it's the term I prefer to use, or in this case, a "leading simultaneous left turn".

The second example, "Alternative Doghouse" is what we call a "leading left", in Ontario and other parts of Canada, mostly eastern Canada I believe, this is traditionally called an "advanced green", this used to be shown in Ontario by flashing green ball lights. More on this later, it relates to the conversation.

The third example, "Alternative Doghouse 2" is usually referred to as a "split phase" when traffic going NB has the light all to themselves, while afterwards SB gets the same thing. Usually put in places where more people want to turn left instead of proceed straight. I'm not much of a fan of this kind of phasing.


There are two more that can be shown with doghouses but one can cause traffic to be yellow trapped.

Yellow Trap Doghouse (Lagging Left)

No LTA/Green Ball
Green LTA/Green Ball (oncoming traffic would face a red ball at this point)
Yellow LTA/Yellow Ball
No LTA/Red Ball

(Also this first example can be combined with the leading left to create what is known as leading-lagging left, dangerous to set up because of a yellow trap)

Lagging Simultaneous Left Turn

No LTA/Green Ball
No LTA/Yellow Ball
No LTA/Red Ball
Green LTA/Red Ball
Yellow LTA/Red Ball

Of course there are such variations to the first two example you provided, where a green ball may appear while a green arrow is there on a leading simultaneous left (essentially allowing one side to jump the gun) opposing traffic in this scenario would have no LTA and be on a red ball.


The FYA allows the lagging left phase as well as a leading-lagging phase to be set up safely, but the issue I have is with how it changes our definitions of the arrows.

So here is my solution

Picture a doghouse signal (or a 4-head signal with a bimodal arrow which we use here) or however this kind of phase is oriented on the signals in your area.

Take the green ball out, and replace it with a FLASHING YELLOW BALL.

Affix what you show to determine when a signal is a fully protected left, such as the "LEFT TURN SIGNAL" sign, or the "lane turns left" sign (you know what I mean, what you see to show which lane goes which direction). Attach this next to the light, and voila you have done it without having ambiguous solid yellow arrows and puzzling flashing yellow arrows.

As for the flashing yellow ball, in Michigan they used to display a flashing red ball during phases of left turns in lights in that state for years, and that did not cause much of a problem.

This way all the traffic rules remain the same, and you have all the benefits of the FYA.


Even if the FYA replace the doghouses which I think is the master plan, consider that the typical "doghouse" signal didn't appear with all the common phases in Ontario until the late 80s/early 90s, instead we used to have an "Advanced Green" where the green ball flashes, this means that opposing traffic faces a red, and the intersection is fully protected from pedestrians as well (essentially it covers a right green arrow too), but of course, drivers from other places were not sure on to what a flashing green meant and well, it was thankfully phased out as you can do a lot more flexible signal phases with the doghouse.

It will take at least 30 years for the traditional doghouse to disappear entirely, i mean it's been over 25 years since the flashing greens were phased out of Ontario, and well this is a video of one I discovered that still runs in the GTA to this day.

My alternative to the FYA eliminates the issues involving the non right of way yellow arrow, I think this is what they should have went for.

[jakeroot]

Filmed this yesterday...my approach to this 5-section signal was skipped because I didn't arrive fast enough...a flashing yellow arrow disregards arrival times, defaulting straight to the flashing mode (unless it's one of those weird jurisdictions that synchronizes the FYA with the through signals -- not the case here). If this turn was a flashing yellow arrow, I could have proceeded, but because cross-traffic arrived first, it received the next green.

https://youtu.be/YA30kMB06cA

[Revive 755]

Take the green ball out, and replace it with a FLASHING YELLOW BALL.

So now this indication now gets some ambiguity, changing from 'proceed with caution' to 'yield'

Affix what you show to determine when a signal is a fully protected left, such as the "LEFT TURN SIGNAL" sign, or the "lane turns left" sign (you know what I mean, what you see to show which lane goes which direction). Attach this next to the light, and voila you have done it without having ambiguous solid yellow arrows and puzzling flashing yellow arrows.

And with the latter sign you have now violated the MUTCD in the US.

[quote author=MisterSG1 link=topic=18124.msg2151574#msg2151574 date=1465927451As for the flashing yellow ball, in Michigan they used to display a flashing red ball during phases of left turns in lights in that state for years, and that did not cause much of a problem.[/quote]

When used in Michigan, the flashing red ball kept it's general mean of 'stop, turn when safe to do so' and did not have any ambiguities of its own introduced.

[tradephoric]

(unless it's one of those weird jurisdictions that synchronizes the FYA with the through signals -- not the case here).

What you consider "˜weird' is standard practice in other parts of the country.  Maybe you are just an intolerant individual.

[jakeroot]

(unless it's one of those weird jurisdictions that synchronizes the FYA with the through signals -- not the case here).

What you consider "˜weird' is standard practice in other parts of the country.  Maybe you are just an intolerant individual.

I think it's weird because it defeats one of the major advantages of the FYA (independent operation of the left turn signal from the through signals). Surely my logic is at least somewhat sound.

[roadfro]

How many agencies suppress the flashing yellow arrow when the adjacent through is displaying a red?  This is common around here.  So if leading lefts terminate non-simultaneous, you will see an extended solid red arrow until the adjacent through turns green.  This setup really doesn't affect capacity since at the start of the opposing through traffic will likely be queued up preventing any permissive turns from being made anyways.

Is there any advantage to suppressing the FYA until the adjacent through comes on though?

One benefit of FYA is tying into the opposing through green by default. I feel like holding the FYA until adjacent through green comes on takes extra programming that isn't necessary (unless it's somehow tied to a phase overlap)...

[roadfro]

So here is my solution

Picture a doghouse signal (or a 4-head signal with a bimodal arrow which we use here) or however this kind of phase is oriented on the signals in your area.

Take the green ball out, and replace it with a FLASHING YELLOW BALL.

Affix what you show to determine when a signal is a fully protected left, such as the "LEFT TURN SIGNAL" sign, or the "lane turns left" sign (you know what I mean, what you see to show which lane goes which direction). Attach this next to the light, and voila you have done it without having ambiguous solid yellow arrows and puzzling flashing yellow arrows.

As for the flashing yellow ball, in Michigan they used to display a flashing red ball during phases of left turns in lights in that state for years, and that did not cause much of a problem.

This way all the traffic rules remain the same, and you have all the benefits of the FYA.

...

My alternative to the FYA eliminates the issues involving the non right of way yellow arrow, I think this is what they should have went for.

Your solution has some other issues though:

Part of the beauty of an FYA display is that you can have all arrow indications to control turning movements, which needs fewer signs next to signal heads. Using a flashing yellow ball for the permissive movement, with adjacent through green balls, introduces other ambiguities. For your idea, you now HAVE TO use a sign with the left turn display, or use louvers over the flashing circular yellow and normal circular yellow, to avoid confusion between a circular indication for left turns versus another circular indication for adjacent through traffic.


Again, the steady yellow indication previously never assigned a right of way. The yellow was an indication that the prior signal phase that allowed a permitted or protected movement is transitioning from green to red. That's it. The only change now is it indicates a transition from green/flashing yellow to red.

[roadfro]

I have a bad feeling that the FYA will eventually supersede the doghouse signal, which thankfully is trying to hang on for as long as possible. FWIW, I prefer the doghouse because it gives a better idea when you can and can't turn left.

All arrow displays for turn lanes will supersede the doghouses for any situation where the left turn has an exclusive signal face (turn lane has its own signal), because the MUTCD now prohibits circular ball indications over dedicated turn lanes. Doghouses are still okay for shared signal faces, where the doghouse is located on the lane line separating a turn lane from a through lane.

I don't see how a doghouse gives you any better idea of when you can/can't turn left than an FYA signal does. It just uses different indications to do it.

[mrsman]

Yellow Trap Doghouse (Lagging Left)

No LTA/Green Ball
Green LTA/Green Ball (oncoming traffic would face a red ball at this point)
Yellow LTA/Yellow Ball
No LTA/Red Ball

(Also this first example can be combined with the leading left to create what is known as leading-lagging left, dangerous to set up because of a yellow trap)

In general, a lagging left does lead to yellow trap, but lagging lefts will not lead to yellow traps when the opposing left is somehow restricted.

- If the opposing left (and u-turn) is prohibited, a permissive lagging left will not lead to yellow trap.  We see this commonly at T-intersections (there is no street for opposing traffic to turn into).  And at one-way streets (opposing left prohibited from turning into one-way traffic).*

- If the opposing left is protected only, a permissive lagging left will not lead to yellow trap.  Often where the left turn is much heavier than the opposing left turn, the signals are set up this way to give the more dominant left turn the permissive indication.  So you will see a protected-only lead left turn combined with a protected/permissive lagging left turn for the heavier turn movement.  Of course the down side is that people making the minor movement will have to wait for that green arrow.

As Brandon had said earlier:

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. 

Since the lagging left is operationally superior, if it can be set up in such a way as to avoid the yellow trap it should be done.

Many lagging lefts use a 4-signal display: R Y G GA.  No need for YA when it is shown at the exact same time as a green.


* Many arterials in the outer boroughs of NYC do this extensively as most minor streets are one-way.  Here is a stretch of Northern Blvd with a lagging left at every signal, even at minor streets:


https://www.google.com/maps/@40.7570836,-73.8703917,3a,75y,277.4h,74.6t/data=!3m6!1e1!3m4!1sIaG1KhQM4Y5n4occoShj6w!2e0!7i13312!8i6656!5m1!1e1!6m1!1e1

[The most current signal has 5 heads, but look at previous years, only 4 heads were used.]

[jakeroot]

- If the opposing left is protected only, a permissive lagging left will not lead to yellow trap.  Often where the left turn is much heavier than the opposing left turn, the signals are set up this way to give the more dominant left turn the permissive indication.  So you will see a protected-only lead left turn combined with a protected/permissive lagging left turn for the heavier turn movement.  Of course the down side is that people making the minor movement will have to wait for that green arrow.

Situations like this are generally avoided in Washington State. Opposing movements, generally, use the same setups. I can't remember what the reasoning is, but I would imagine it's to prevent driver confusion ("if they can go why can't I?"). This is most often observed when there are dual turn lanes opposite a single left turn lane (both will use protected-only).

[JMAN_WiS&S]

Quick question about Dallas phasing, when getting the protected arrow, did the green ball illuminate simultaneously just like on a regular 5stack?

[Revive 755]

All arrow displays for turn lanes will supersede the doghouses for any situation where the left turn has an exclusive signal face (turn lane has its own signal), because the MUTCD now prohibits circular ball indications over dedicated turn lanes. Doghouses are still okay for shared signal faces, where the doghouse is located on the lane line separating a turn lane from a through lane.

Technically doghouses and towers can still be used in front of left turn lanes since the statement on not putting circular greens left of the edge of a left turn lane is only a "should" statement:

Guidance:
09 For new or reconstructed signal installations, on an approach with an exclusive turn lane(s) for a left-turn (or U-turn to the left) movement and with opposing vehicular traffic, signal faces that display a CIRCULAR GREEN signal indication should not be post-mounted on the far-side median or mounted overhead above the exclusive turn lane(s) or the extension of the lane(s).

It is when the left turn is controlled separately (such as having to remain red while the adjacent through movement gets a green) that a doghouse or tower is prohibited - see 4D.17 Paragraph 10 Item B, Paragraph 4D.18 Paragraph 02, and 4D.20 Paragraph 02 in the MUTCD.

I don't see how a doghouse gives you any better idea of when you can/can't turn left than an FYA signal does. It just uses different indications to do it.

A traditional doghouse or tower is much less clear than a FYA head on when left turns are allowed since it has two different indications active at the same time during the protected part of the phase - a red ball and a green arrow - while a FYA head only has a green arrow displayed during the protected mode.  I'm pretty sure this is documented in some of the research on using FYA displays.

[mrsman]

- If the opposing left is protected only, a permissive lagging left will not lead to yellow trap.  Often where the left turn is much heavier than the opposing left turn, the signals are set up this way to give the more dominant left turn the permissive indication.  So you will see a protected-only lead left turn combined with a protected/permissive lagging left turn for the heavier turn movement.  Of course the down side is that people making the minor movement will have to wait for that green arrow.

Situations like this are generally avoided in Washington State. Opposing movements, generally, use the same setups. I can't remember what the reasoning is, but I would imagine it's to prevent driver confusion ("if they can go why can't I?"). This is most often observed when there are dual turn lanes opposite a single left turn lane (both will use protected-only).

IMO, when there are multiple left turn lanes, I am more inclined to only allow the left turns at different time periods. In many cases, if I am in the inside turn lane and needing to turn wide onto the other street, I am worried about the inside lane left turner who is opposing me.  If the green arrows are on simultaneously, we can be close to crossing paths.  In a jurisdiction with protected only for multiple left turn lanes, this is a good candidate for lead-lag operation

[MisterSG1]

I will address a bunch of people over several posts, as I have some catching up to do.

Take the green ball out, and replace it with a FLASHING YELLOW BALL.

So now this indication now gets some ambiguity, changing from 'proceed with caution' to 'yield'

Affix what you show to determine when a signal is a fully protected left, such as the "LEFT TURN SIGNAL" sign, or the "lane turns left" sign (you know what I mean, what you see to show which lane goes which direction). Attach this next to the light, and voila you have done it without having ambiguous solid yellow arrows and puzzling flashing yellow arrows.

And with the latter sign you have now violated the MUTCD in the US.

[quote author=MisterSG1 link=topic=18124.msg2151574#msg2151574 date=1465927451As for the flashing yellow ball, in Michigan they used to display a flashing red ball during phases of left turns in lights in that state for years, and that did not cause much of a problem.

When used in Michigan, the flashing red ball kept it's general mean of 'stop, turn when safe to do so' and did not have any ambiguities of its own introduced.
[/quote]

The way how I deduced what the FYA meant was from the flashing yellow ball. Obviously, if we had a FRA, that would mean the exact same thing of what used to be the standard in Michigan.

As for the flashing yellow ball and proceed with caution, try to imagine this, you are turning left at an intersection that has a flashing yellow ball, either on a beacon or at an intersection after hours, obviously, you cannot make this left turn unless you yield the right of way. So in essence, the flashing yellow ball means exactly that if it were applied to a left turn signal.

In Ontario and some other Canadian provinces as I posted earlier, we used to have a flashing green ball as the standard at some traffic signals, if you apply the logic regarding the flashing red ball and flashing yellow ball, thus the flashing green ball would show that you indeed have right of way, and can indeed make the left turn WITHOUT yielding the right of way.