Has the flashing yellow left turn signal made it to your state?

[johndoe]

Lowell: I'm not sure when they replaced the signals at this intersection, but the FYA at this intersection isn't wired correctly. The left turn with the FYA is across railroad tracks. It isn't wired to the oncoming greens like it is supposed to be. The opposing direction has a protected only left turn.

Could you be specific about the issue? Yes, it should be tied to the oncoming green, but I'm curious what kind of issues are arising as a result.

The FYA on SB Dutton does not flash whenever the oncoming green is lit. This could cause yellow trap if:

- the left turn phase from NB Dutton to WB Broadway provides a green arrow if there are no cars waiting on Broadway (phase skip).
- Not sure how the railroad preemption works at this intersection, but if a train is coming and trips the signal, the FYA on SB Dutton could be wrongfully terminated while NB Dutton still has a green if there is no all-red clear.

This is the first time I have ever passed thru this intersection heading southbound, as I usually go thru on Dutton in the northbound direction, so I'm not sure when the FYA signals were installed. It seems like it was installed in 2019 based on previous GSV history.

Are you saying the SBL FYA seems to be wired to the SBT rather than NBT?  I wonder why they didn't add FYA NBL.

I'd be surprised if the train doesn't have its own phase (since there is no NBR lane a green ball being shown simultaneously with NB train seems less than ideal)

[johndoe]

I've wondered why California would prohibit displaying these signs at intersections with a yellow trap, especially in cases like this (rail preemption). Except for the occasional intersection that has rail or fire preempt, I'm guessing that this sequence is rare as they have a lot of protected-only lefts over in CA...

Ideally, yellow trap should be avoided even with railroad preemption. I don't understand, at your linked examples, why there is a recurring issue with yellow trap. Clearly someone has set something up wrong.

I suspect the signs "shall not be used" because yellow trap (as it may say somewhere else in California's manual) "shall not be used" either. Ergo, no need for the sign. This section operates under the assumption that the sign will not be used because the situation warranting the sign would not arise in California. There clearly was no thought given to the possibility of an engineer not programming an intersection correctly. Although I think an engineer, upon discovering the yellow trap, would instead fix the intersection programming, instead of simply putting up some signs that drivers may or may not notice.

It is really surprising to see it in CA as they are really careful to avoid yellow trap generally.  The NB to WB left turn at Broadway/California in Burlingame has to be converted to a FYA to prevent the yellow trap.   The opposing left, which is currently protected only lagging left could be transformed to a protected/permissive lagging left, but it needs to stay lagging to clear the intersection so as not to block the railroad tracks.

It is surprising that 3 out of the four lefts here are protected only.  The most dangerous left (because of the yellow trap) doensn't have the protection.

So do we assume that SBL usually leads, but the preemption could make it lag (and trap the NBL)? 

I was thinking "get rid of SBL" but assuming the preemption turns off the NBT it's not really the SBL's fault that NBL gets trapped.

Let's say budget is a problem and they wanted to make a quick fix.  They could either disallow the NBL or split-phase NB vs SB with relatively low costs. 

[mrsman]

I've wondered why California would prohibit displaying these signs at intersections with a yellow trap, especially in cases like this (rail preemption). Except for the occasional intersection that has rail or fire preempt, I'm guessing that this sequence is rare as they have a lot of protected-only lefts over in CA...

Ideally, yellow trap should be avoided even with railroad preemption. I don't understand, at your linked examples, why there is a recurring issue with yellow trap. Clearly someone has set something up wrong.

I suspect the signs "shall not be used" because yellow trap (as it may say somewhere else in California's manual) "shall not be used" either. Ergo, no need for the sign. This section operates under the assumption that the sign will not be used because the situation warranting the sign would not arise in California. There clearly was no thought given to the possibility of an engineer not programming an intersection correctly. Although I think an engineer, upon discovering the yellow trap, would instead fix the intersection programming, instead of simply putting up some signs that drivers may or may not notice.

It is really surprising to see it in CA as they are really careful to avoid yellow trap generally.  The NB to WB left turn at Broadway/California in Burlingame has to be converted to a FYA to prevent the yellow trap.   The opposing left, which is currently protected only lagging left could be transformed to a protected/permissive lagging left, but it needs to stay lagging to clear the intersection so as not to block the railroad tracks.

It is surprising that 3 out of the four lefts here are protected only.  The most dangerous left (because of the yellow trap) doensn't have the protection.

So do we assume that SBL usually leads, but the preemption could make it lag (and trap the NBL)? 

I was thinking "get rid of SBL" but assuming the preemption turns off the NBT it's not really the SBL's fault that NBL gets trapped.

Let's say budget is a problem and they wanted to make a quick fix.  They could either disallow the NBL or split-phase NB vs SB with relatively low costs.

I think what you are saying is that the SB lagging left is a symptom of the yellow trap - the real cause is that SB thru has green after the time that NB green terminates (in order to clear traffic from the RR crossing).  I agree with this assessment.  NB sees red so NB left turners assume that SB also has red, but they don't really have a red so its a yellow trap.

Three treatments for the NB left turn are usually utilized to address a yellow trap situation:

Prohibit the left turn:  No left turn signs put in place.  This is the cheapest option. 

Restrict the left turn:  NB left turn to only be allowed on a green arrow.  Sometimes this means a protected only leading left.  Alternatively, it could mean split-phasing as you suggest.  But at the time when SB has green, NB may not turn left at all.

Control the left turn:  Utilizing the flashing yellow arrow.  If drivers on the NB left focus on the flashing yellow arrow, they will realize that they still have to yield to oncoming traffic even though adjacent singals are turning red.  The DOT can choose between a 4 aspect FYA signal (to allow for a protected leading green arrow) or a 3 aspect FYA signal just to address the yellow trap safety issue without a new protected phase.

The status quo is awful.  We should not introduce a new safety problem (yellow trap) to address the current safety problem (cars stopped on RR tracks).  Fortunately, there are ways to address the issue, but it doesn't seem like we can get the attention of the local DOT in Burlingame.

[mrsman]

While not a FYA, the discussion in my previous post about yellow trap brought to mind this situation in Queens, NYC.

The intersection of Metropolitan Ave and Park Lane South*:

Let's start with the 2007 view:

https://www.google.com/maps/@40.7079216,-73.8371185,3a,75y,240.47h,81.06t/data=!3m6!1e1!3m4!1sFPyeRgXfTijI5CMV2tC8tQ!2e0!7i3328!8i1664

Nothing remarkable.  E-W Metropolitan Ave intersects with N-S Park Lane South.  There is a NB to WB protected/permissive leading left signalized with a 8-8-8-12-12 tower on the side and a NYC style 12-12/8-8-8 doghouse overhead.

Now let's advance to the present day.  For pedestrian safety, the city is implementing leading pedestrian intervals in many places.  But they realize that leading pedestrian intervals are incompatible with leading protected signals, so they convert them to lagging left signals.  But, a lagging left signal if not properly designed could lead to yellow trap.  So what is the solution? They could use any of the three options, I mentioned in the previous post, for the opposing left and they decided to prohibit the opposing left turn.

https://www.google.com/maps/@40.7080872,-73.837112,3a,75y,214.74h,76.91t/data=!3m6!1e1!3m4!1sLTInk6DAS6dncCkou8mDIQ!2e0!7i16384!8i8192

As you can see, there is enough room to stripe a left turn lane here for the now prohibited SB to EB left turn.  Moreover, they changed the left turn signal to a 4-aspect signal that used to be common for lagging lefts (but now prohibited by MUTCD).  8-8-8-12 on the side and 12/8-8-8 on the overhead.

Given the penchant for breaking rules in NYC, especially as someone can make the left turn while parked in the median lane (so as not to block thru traffic), I think it was an unnecessary mistake to prohibit the SB to EB left turn.  This would have been a good case for a FYA.  Obviously, the prohibition was chosen as being the cheapest option




* Based on addresses they are both E-W streets, but given that they meet at right angles, and Metropolitan is closer to due E-W, I use that terminology above.

[Amtrakprod]

While not a FYA, the discussion in my previous post about yellow trap brought to mind this situation in Queens, NYC.

The intersection of Metropolitan Ave and Park Lane South*:

Let's start with the 2007 view:

https://www.google.com/maps/@40.7079216,-73.8371185,3a,75y,240.47h,81.06t/data=!3m6!1e1!3m4!1sFPyeRgXfTijI5CMV2tC8tQ!2e0!7i3328!8i1664

Nothing remarkable.  E-W Metropolitan Ave intersects with N-S Park Lane South.  There is a NB to WB protected/permissive leading left signalized with a 8-8-8-12-12 tower on the side and a NYC style 12-12/8-8-8 doghouse overhead.

Now let's advance to the present day.  For pedestrian safety, the city is implementing leading pedestrian intervals in many places.  But they realize that leading pedestrian intervals are incompatible with leading protected signals, so they convert them to lagging left signals.  But, a lagging left signal if not properly designed could lead to yellow trap.  So what is the solution? They could use any of the three options, I mentioned in the previous post, for the opposing left and they decided to prohibit the opposing left turn.

https://www.google.com/maps/@40.7080872,-73.837112,3a,75y,214.74h,76.91t/data=!3m6!1e1!3m4!1sLTInk6DAS6dncCkou8mDIQ!2e0!7i16384!8i8192

As you can see, there is enough room to stripe a left turn lane here for the now prohibited SB to EB left turn.  Moreover, they changed the left turn signal to a 4-aspect signal that used to be common for lagging lefts (but now prohibited by MUTCD).  8-8-8-12 on the side and 12/8-8-8 on the overhead.

Given the penchant for breaking rules in NYC, especially as someone can make the left turn while parked in the median lane (so as not to block thru traffic), I think it was an unnecessary mistake to prohibit the SB to EB left turn.  This would have been a good case for a FYA.  Obviously, the prohibition was chosen as being the cheapest option




* Based on addresses they are both E-W streets, but given that they meet at right angles, and Metropolitan is closer to due E-W, I use that terminology above.

How is it not possible to having a leading left and LPI.

You give a leading left and straight but first the crosswalk signal on the right of that leading left starts up. Oh wait as I'm typing this I realize why. Since you can't show a red arrow left. We have too many FYAs near me now that I forget that


iPhone

[mrsman]

While not a FYA, the discussion in my previous post about yellow trap brought to mind this situation in Queens, NYC.

The intersection of Metropolitan Ave and Park Lane South*:

Let's start with the 2007 view:

https://www.google.com/maps/@40.7079216,-73.8371185,3a,75y,240.47h,81.06t/data=!3m6!1e1!3m4!1sFPyeRgXfTijI5CMV2tC8tQ!2e0!7i3328!8i1664

Nothing remarkable.  E-W Metropolitan Ave intersects with N-S Park Lane South.  There is a NB to WB protected/permissive leading left signalized with a 8-8-8-12-12 tower on the side and a NYC style 12-12/8-8-8 doghouse overhead.

Now let's advance to the present day.  For pedestrian safety, the city is implementing leading pedestrian intervals in many places.  But they realize that leading pedestrian intervals are incompatible with leading protected signals, so they convert them to lagging left signals.  But, a lagging left signal if not properly designed could lead to yellow trap.  So what is the solution? They could use any of the three options, I mentioned in the previous post, for the opposing left and they decided to prohibit the opposing left turn.

https://www.google.com/maps/@40.7080872,-73.837112,3a,75y,214.74h,76.91t/data=!3m6!1e1!3m4!1sLTInk6DAS6dncCkou8mDIQ!2e0!7i16384!8i8192

As you can see, there is enough room to stripe a left turn lane here for the now prohibited SB to EB left turn.  Moreover, they changed the left turn signal to a 4-aspect signal that used to be common for lagging lefts (but now prohibited by MUTCD).  8-8-8-12 on the side and 12/8-8-8 on the overhead.

Given the penchant for breaking rules in NYC, especially as someone can make the left turn while parked in the median lane (so as not to block thru traffic), I think it was an unnecessary mistake to prohibit the SB to EB left turn.  This would have been a good case for a FYA.  Obviously, the prohibition was chosen as being the cheapest option




* Based on addresses they are both E-W streets, but given that they meet at right angles, and Metropolitan is closer to due E-W, I use that terminology above.

How is it not possible to having a leading left and LPI.

You give a leading left and straight but first the crosswalk signal on the right of that leading left starts up. Oh wait as I'm typing this I realize why. Since you can't show a red arrow left. We have too many FYAs near me now that I forget that


iPhone

I think you got the point, but let me elaborate for the others.

Keep in mind this is NYC, where RTOR is generally illegal.  Thus, an LPI (leading pedestrian interval) provides 3 seconds (or so) of complete protection for pedestrians.  No conflicting vehicular movement of any kind during those 3 seconds.

OK, so if we have a permissive leading left with a doghouse (or 5 aspect tower or other equivalent), you have the left turners going first.  Once the protected phase has ended, then they can make a left in the permissive phase.  If we were to then allow the LPI to go, opposing traffic has a red, but the left turn traffic sees a green orb.  The drivers are smart and they will figure out that they can make that left, even though only a green orb shows, since opposing traffic will have a red for 3 additional seconds.  They can make the left but will bully the pedestrians in the process.  Not the goal of an LPI, which again in NYC is conflict free.

You are totally correct that well placed FYA signals can address these problems.  An FYA SB, opposing the protected/permissive lagging left, would mean that we would no longer have to prohibit the SB to EB movement.  An FYA NB would mean, as you suggest, that you can have a leading  protected/permissive left that precedes the LPI.  During the LPI, opposing thru traffic and the left arrow would be red and when the LPI ends, we will have a FYA that is concurrent with opposing  green.

Of course, every new signal head costs money.  If one wanted to maximize throughput while still allowing for an LPI, you would produce FYA signals to govern every left and right turn possible at this intersection, so that  could be quite costly.  In Manhattan, that is done more frequently, but usually on turns from a street to an avenue (not the other way around) or in conjunction with protected bike lanes.  But due to the heavier traffic and the one-way streets (thereby needing fewer FYA signal faces), this is done there, but cannot be done at quieter intersections like the above in Queens.  So an LPI that even holds back thru traffic that won't conflict with the peds is implemented instead.

So when all is said and done, a CHEAP LPI is implemented the way that NYC did it.  But then again, I believe the SB to EB left turn should still be allowed with a FYA signal to avoid yellow trap, as opposed to the prohibtion actually implemented by NYC.

[johndoe]

How is it not possible to having a leading left and LPI.

...if we have a permissive leading left with a doghouse (or 5 aspect tower or other equivalent), you have the left turners going first.  Once the protected phase has ended, then they can make a left in the permissive phase.  If we were to then allow the LPI to go, opposing traffic has a red, but the left turn traffic sees a green orb. 

Maybe my brain hasn't fully woken up yet, but I'm not following this.  Are you saying that 5 section PPLT should NEVER have LPI?  Or this spot is bad in particular?  I thought for awhile you were worried about a yellow trap, but after reading it a few times it seems you're saying that LPI doesn't exist for the side where the green through comes on later.  I think I get that point now, but I would argue that allowing permissive lefts (or rights, for that matter) across a walk signal isn't "conflict free".  If anything I feel like LPI gets peds out the middle of the intersection and then allows the turning movements 

My guess is that any signal head addition would have cost too much (maybe new equipment would have been required or they would have been forced to follow the newest rules).  Maybe apart from the LPI they wanted to go lagging NBL so that it doesn't come on every phase (if it can find gaps in the SBT) but IMO that isn't worth prohibiting the SBL 24/7.

[mrsman]

First, I found a very effective document put out by NYCDOT on the improvements when they presented them to the community board.  Check out pages 12-14 on this intersection.

http://www.nyc.gov/html/dot/downloads/pdf/park-lane-s-feb-2017.pdf

In NYC, the LPI is conflict free, by design, during the first few seconds when it is active.

Let's take a generic intersection, without protected lefts.  For vehicles, the LPI is basically an extended all-red phase that will exist prior to N-S traffic getting a green and prior to E-W traffic getting a green.  For those few seconds all vehicles see red and since in NYC, NTOR, no cars will be moving during those 3 seconds.  Of course, when the signal turns green rights are permitted (yielding to pedestrians) and lefts are permitted (yielding to oncoming traffic and pedestrians) but the pedestrians will already be in the intersection (and more visible to cars).  This is the purpose of the LPI, to allow the pedestrians to get a head start to prevent cars from "bullying" pedestrians from even stepping off the curb.  The LPI is brief, so yes only a sprinter would be able to get all the way across the street before parallel traffic is released, but that's not the purpose.  In fact, NYC generally avoids all-pedestrian "Barnes Dance" phases since they would cause too much delay.  This report analyzes and discourages their use.

http://www.nyc.gov/html/dot/downloads/pdf/barnes-dance-study-sept2017.pdf

Let me see if I can now address johndoe's points:

Maybe my brain hasn't fully woken up yet, but I'm not following this.  Are you saying that 5 section PPLT should NEVER have LPI? 

In short answer, yes.  Since the LPI is short, if we were to put it in place, it needs to follow the green arrow.  If you put the LPI right after the green arrow, pedestrians would be protected from SB right turners but NB left turners would still be allowed to turn during the LPI.  Those 3 seconds are not fully protected.  But if an FYA signal were put in its place, you could have a sequence of GA, YA, RA (brief), FYA, YA, RA - where the LPI occurs during the brief RA phase that follows the GA, before oncoming green and FYA are released.  IMO, that would be preferable, since they would still be able to allow for the SB left turn without yellow trap.

THe above discussion only affects the west side sidewalk.  The east side sidewalk is totally unaffected as there is no protected green in conflict.  An LPI can be achieved  on that side, even with a NB 5 aspect leading PPLT.  During the 3 second LPI, NB signals show WALK, red orb, and green left arrow.  The green orb would begin 3 seconds later.  Because of the NTOR, there is no conflict for pedestrians on the east sidewalk at all during the 3 second LPI.

I thought for awhile you were worried about a yellow trap, but after reading it a few times it seems you're saying that LPI doesn't exist for the side where the green through comes on later. 

I think I get that point now, but I would argue that allowing permissive lefts (or rights, for that matter) across a walk signal isn't "conflict free".  If anything I feel like LPI gets peds out the middle of the intersection and then allows the turning movements 

While not as safe as all pedestrian phase, it is far easier for traffic to see the peds when they are in the middle of the intersection, then when they may or may not be stepping off the curb.  In NYC, "bullying" is a problem - cars will turn right when the light turns green to prevent pedestrians from beginning to cross the street.  If the pedestrains are given a "head start" they will be forced to yield to them.  An all pedestrian phase isn't practical as a widespread measure, since it would cause too much delay.  LPIs are very widespread in NYC, since the delay to the intersection is minimal.

My guess is that any signal head addition would have cost too much (maybe new equipment would have been required or they would have been forced to follow the newest rules).  Maybe apart from the LPI they wanted to go lagging NBL so that it doesn't come on every phase (if it can find gaps in the SBT) but IMO that isn't worth prohibiting the SBL 24/7.

While NYC is innovative in some ways, in other ways, it is behind.  I am not aware of a single intersection in the city where there are any sensors that change the traffic display based on existing conditions.  Every signal is operated by a timer that has probably been around since the 1950s.  Now the timers can be programmed (or modernized) to add green arrows, but they don't sense real world conditions.  The lagging left comes on every cycle, even if there are no cars wanting to turn left.  It is definitely a cheap out, because a well placed FYA signal (either a NB 4 aspect leading PPLT or a SB 3 aspect w/o protection) could allow the SB left to still be a safe  turn.  And given what I know of NYC drivers, a lot of people will make that SB left turn despite the no left turn prohibition and they would do so in the face of a yellow trap thanks to the now lagging left in the NB direction.

[johndoe]

Thanks for the link.  I didn't even consider that there weren't detectors at the intersection, but that kind of goes along with the "don't have funds for signal improvements" if they're just running pretimed 24/7.  I get the goal of the LPI but very few intersections around here have NYC levels of peds- I could see how it would at least clarify for drivers which pedestrians are actually crossing and which are waiting for the other crossing direction.

Out of curiosity, have you seen other examples where entities avoid 5 section PPLT and LPI?  Personally I think if the organization is okay with permissive turns (circular green / FYA) conflicting with walk signals, it doesn't really matter if it happens at the beginning of LPI or just the rest of the split.

[mrsman]

Thanks for the link.  I didn't even consider that there weren't detectors at the intersection, but that kind of goes along with the "don't have funds for signal improvements" if they're just running pretimed 24/7.  I get the goal of the LPI but very few intersections around here have NYC levels of peds- I could see how it would at least clarify for drivers which pedestrians are actually crossing and which are waiting for the other crossing direction.

Out of curiosity, have you seen other examples where entities avoid 5 section PPLT and LPI?  Personally I think if the organization is okay with permissive turns (circular green / FYA) conflicting with walk signals, it doesn't really matter if it happens at the beginning of LPI or just the rest of the split.

And then at some intersections, they do incorporate a FYA, even when not strictly needed.  This intersection, 108th and LIE service road, incorporates FYA on a lagging turn. 

https://www.google.com/maps/@40.7371401,-73.8517664,3a,75y,145.56h,78.76t/data=!3m7!1e1!3m5!1sToUAVWVZoUc9wSa1BqZsmg!2e0!5s20191101T000000!7i16384!8i8192

Before the FYA, it was signaled with a 4-aspect R-Y-G-GA that is common for lagging permissive turns.  (See an older GSV for the same location.)  While the FYA is nice, I don't view it as being necessary since there is no yellow trap problem given the one-way nature of the LIE service roads.  The old signals could have been kept here and the signal modernization funds IMO could have been used for FYA at Met/Park Ln S to avoid prohibiting the SB to EB left.  But they don't consult with me for these decisions.

I don't beleive I've seen the avoidance of LPI and 5 section leading PPLT in a similar context elsewhere (i.e. outside of NYC).  I am aware of at least one other NYC example. 

Generally, if pedestrian crossing is a big concern with respect to a permissive left, the usual way of handling it would be to make the turn protected only.  A protected only turn would not have any conflict with LPI.

[SignBridge]

Interesting how NYC is trying to adapt their antiquated mast-arm signals to the more modern practices.

[Amtrakprod]

Yay MA now has installed its first FYA with a bimodel arrow at the bottom. I'll come here again soon to get video.


iPhone

[mrsman]

Interesting how NYC is trying to adapt their antiquated mast-arm signals to the more modern practices.

Good for noticing.  In NYC the standard approach has been to hang two mast arm signals on opposite diagonal corners so that the signal heads both hang over the intersection.  Each signal head is potentially a 4-way signal (but because of the prevalence of one way streets at least one of the ways isn't shown).  You still see two signal heads from every direction, but the placement is a little off, designed so that each direction can see the singal head, but not that each direction can see the signal head well.

If a 4-aspect or 5 aspect left turning signal is added (RYG-GA or RYG-YA-GA) usually the mast arm signal on the left will also have placement for the arrows.  To supplement this, a side mounted (or median mounted) pole signal will supplement the signal so that there are at least two signal heads for the turn signal.  (See the GSVs at Met/park Ln S and the older pics of 108th/LIE).  To go from this state to FYA (or protected only RA-YA-GA), you can simply convert the side mounted signal to a 4 aspect FYA, convert the left side signal to a 4 aspect FYA, and then somehow add an additional RYG signal on the right far side.  Compare the old and the new signals at 108th/LIE from my post yesterday to illustrate this.

So it really shouldn't be too hard to convert a leading PPLT "doghouse" to a leading PPLT FYA arrangement.  This should be done to the extent that the leading arrow is on one side of the intersection if it is desirable to implement LPI.  There is no reason to prohibit the opposing left turn in this scenario.

[kphoger]

I saw my first FYAs in the Wichita area.  (Perhaps there already were some, but I hadn't seen any until last week.)  At least two intersections on Rock Road in Derby (Madison Ave & James St) have had their stoplights changed from doghouses to FYAs.

[Amtrakprod]

How do state DOTs change FYAs.

Is MA the only state that funded to replace 5 sections to FYAs at 350 intersections or did other states have a process like this:

Example or an installed:

Old:

Had 3 signals.

Left on cantilever was a 5 section doghouse.
Right on top of the cantilever is a 3 section signal (still there)
And on the right of the middle of the pole another 3 section RYG signal. (Still there)
Now:


Another example:

Old set up. Two signals on the cantilever. 1 doghouse and one 3 section RYG (still there).

Now:
MassDOT even adds in an extra signal to comply with the MUTCD, I swear we are definitely improving traffic light wise. We aren't at IL standards yet, but soon I hope. (Atleast we have widespread FYA)


iPhone

[roadfro]

How do state DOTs change FYAs.

Is MA the only state that funded to replace 5 sections to FYAs at 350 intersections or did other states have a process like this:

Several years ago, Nevada DOT doled out some money to local municipalities (primarily to Carson City, Reno/Sparks, and the Las Vegas area) to convert 5-section PPLT displays to 4-section FYAs–I think it was part of some safety enhancement programming dollars. Not all instances were converted (I'm guessing some of the first ones that were changed were likely higher-crash locations).

Nevada is usually very good with left turn signal placement (one centered overhead in front of the turn lane, and a supplemental far left post-mount), and there are very few examples of "shared" 5-section left turn displays. Because of this, most of these conversions simply changed out the existing left turn signal heads and any associated signs on the mast arm. (An advantage to "signal per lane" design philosophy in this case, since it's not necessary to move/reposition/add other through signal heads to comply with MUTCD when a signalization change like this occurs.)

[jakeroot]

Nevada is usually very good with left turn signal placement (one centered overhead in front of the turn lane, and a supplemental far left post-mount), and there are very few examples of "shared" 5-section left turn displays. Because of this, most of these conversions simply changed out the existing left turn signal heads and any associated signs on the mast arm. (An advantage to "signal per lane" design philosophy in this case, since it's not necessary to move/reposition/add other through signal heads to comply with MUTCD when a signalization change like this occurs.)

In most circumstances in states that do place shared signals over the lane divider, a mast arm extension seems to be the most common modification (either by extending the mast arm, or using another similar (but thinner) part), but sometimes, even with two lanes, the right-most three-section signal remains and the 5-section display is replaced with an FYA signal that (not permissibly?) sits over the lane divider; an extra far-right mast-mounted signal is used instead, to meet the requirement for two through signals (in my WA example, there is only one overhead signal for two lanes, but there is a new signal on the right mast).

edit: clarification.

[Amtrakprod]

Filmed that bi model FYA in MA:


https://youtu.be/5Xf_zZkm3jw


iPhone

[doorknob60]

One thing that makes me less quick to jump on FYAs is that, unlike left turns where there is no left turn arrow at all, traffic seems slightly less apt to pull forward. Even in areas that I deem relatively conservative, drivers will always pull forward to turn on solid green lights where there is no protected phase (how else can you guarantee you'll make it?), but the split more like 75 (forward)/25 (behind the line) at FYAs. There have been more than a few situations where I missed a left turn because the driver in front refused to enter the junction, where I know they would have, had the light not had a green arrow phase. Some drivers fully embrace the concept of "I'll just wait for the green arrow if there's no gap" style of driving that seems to pop-up when I see an FYA installed.

Those people would have some problems in some areas because some FYAs never turn green in their current operation (with possible exceptions for emergency vehicles, not sure). For example, almost every FYA in downtown Boise (there are quite a few) will not give you a green arrow, and some outside of downtown as well, such as at Emerald St and Roosevelt St (an intersection I used to use daily before I started working from home).

ACHD's current policy seems to be putting a dedicated left turn signal (usually FYA if it's a single lane) over every dedicated left turn lane, even if the intersection is not planning on having a protected turn. A "left turn yield on green" setup will usually only be done if the road doesn't have a left turn lane (see Jefferson or Bannock St in downtown Boise for examples). There's older installations out there with turn lanes and just a regular ball signal, but they're disappearing and you won't see that at new installations.

From your post, I decided to GSV around Downtown Boise and came across 13th and Bannock:

https://www.google.com/maps/@43.6201144,-116.2078919,3a,75y,296.92h,86.55t/data=!3m6!1e1!3m4!1s0kNyzg7SdeMq2wmefiWqtA!2e0!7i13312!8i6656

The signage is so interesting to me.  It seems that there are two-way traffic signs up and down 13th.  I understand it may be one of the few two-way streets, but it is odd to me to sign what should be the "normal" condition. 

On top of that, you see "left turn yield on green" for streets without FYA, but no sign accompanying the FYA.  I guess in Boise the FYA is so ingrained that they have to instruct drivers what to do when you don't have one.  This is also weird to me, as I grew up (in 80s and 90s Los Angeles) with the notion that a normal traffic signal does not have a left turn arrow of any kind and that yielding on green is normal.  The yield on green was put up at doghouse singals (if at all) to remind people that they could turn on green with a yield and that they did not need to wait for the green arrow.  (Especially important in CA with very many signals in rural and suburban areas that were protected only left arrows.)  And FYAs needed similar signage because they were relatively new and people did not understand how they operate (and we still have some states that don't allow the FYA).  Here's an example in Pasadena, CA.

https://www.google.com/maps/@34.1275808,-118.1472417,3a,75y,259.34h,79.05t/data=!3m6!1e1!3m4!1sR-DcEibSX2I0WYxPDeOMQQ!2e0!7i13312!8i6656

I notice from GSVing that the FYAs in Boise are 4 aspect FYAs for the most part.  Are you saying that the green arrow never comes on or only rarely comes on (certain times of day or a large number of people waiting to turn left)?  Some areas have put in place the 3 aspect FYA (RA-YA-FYA) with no room for a green arrow, since no protected turn is even programmed. (Someone recently posted a picture of one in Kansas, with no obvious reason for a 3 aspect FYA other than the fact that they now need a dedicated left turn signal at each left turn lane.  It seemed odd to me.)

Those 2 way signs on 13th and Bannock I believe are only there because those streets used to be one way. I believe it was somewhere around 2013-2015 they were changed to two way, not entirely sure (I didn't frequently visit downtown until after that). Jefferson was converted from one way to two way more recently, I think 2017 or 2018, it may have similar signage too. EDIT: Looking at GSV history, looks like Bannock has been 2 way since before 2007, but 13th (and 12th) were converted around 2015.

The "Left turn yield on green" signs are pretty much standard at any permissive left turn with green balls I can think of around here, also including doghouses. I remember that being the case in most of Oregon as well. It's just common practice to put those signs. I suppose FYAs are less ambiguous and don't need additional signs. It's certainly true that at least here, everyone seems to know how to use them.

And yes, you are correct that there are 4 section FYA heads around here that will never show a green arrow ever (unless they get re-programmed later, or presumably if an emergency vehicle drives through). I don't think there are any 3 section FYAs in Ada County, which is good because I'm not a big fan of them personally.

[Amtrakprod]

Saw this in Austin TX. February 18th in an Uber


iPhone

[jakeroot]

Saw this in Austin TX. February 18th in an Uber

I've only seen one flashing yellow U-turn arrow, and it's in University Place, WA, southbound Bridgeport Way at Chambers Creek Road.

The original signal (seen here looking east from the side street) was protected only for the regular left, and there was no U-turn, but a median was installed along Bridgeport in preparation for the US Open back in 2015 (to "beautify" the area), necessitating a U-turn maneuver at this intersection. Weirdly, and only if I recall correctly, this (alongside the opposing regular FYA) were the first two flashing yellow signals in University Place. Not sure how many jurisdictions can claim that their first FYA installation included a U-turn FYA!

[Amtrakprod]

Saw this in Austin TX. February 18th in an Uber

I've only seen one flashing yellow U-turn arrow, and it's in University Place, WA, southbound Bridgeport Way at Chambers Creek Road.

The original signal (seen here looking east from the side street) was protected only for the regular left, and there was no U-turn, but a median was installed along Bridgeport in preparation for the US Open back in 2015 (to "beautify" the area), necessitating a U-turn maneuver at this intersection. Weirdly, and only if I recall correctly, this (alongside the opposing regular FYA) were the first two flashing yellow signals in University Place. Not sure how many jurisdictions can claim that their first FYA installation included a U-turn FYA!

Pretty cool! Kinda weird it's not a protected left.


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[Amtrakprod]

Another from austin. Weird thing is the opposing left turn is protected.


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[mrsman]

Do you know if the left turn on the opposite sides of those FYA U-turns are leading or lagging?  Many times lagging left turns are designed at T intersections because there is no potential for yellow trap since there is no place for the opposing traffic to go (assuming that u-turns are not allowed).

Perhaps, originally the u-turns here were disallowed and the opposing left was lagging, but when they decided to permit the u-turn (to access businesses that are blocked by the median), a FYA is needed to prevent yellow trap.

[fwydriver405]

MaineDOT is finally starting to use the FYA and phasing out the 5-section doghouses in (some of) their new installs... AFAIK the signal improvement projects in Waterville and in Old Town are even including 3-section permissive FYA's for those approaches that don't require a permissive phase!

Now if only they used right-turn FYA's in Old Town for the approches that have right turn lanes, an overlap, and an LPI as seen in the plans below:

Old Town - Stillwater Ave at Bennoch Rd and College Ave, near the University of Maine