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Double left turns with permissive phasing

Started by jakeroot, December 14, 2015, 02:01:17 AM

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Do you think dual permissive turns should be allowed?

Yes
57 (50.4%)
No
35 (31%)
Cat
21 (18.6%)

Total Members Voted: 113

mrsman

Quote from: jakeroot on April 14, 2019, 03:39:20 AM
Quote from: mrsman on April 14, 2019, 01:01:36 AM
Is there anybody out inthe Cupertino area who can verify that the signal actually operates in this way, i.e. that the traffic signals facing the driveways coming from the north and the south are green at the same time such that the double left turn has to be made against opposing traffic?

While that is a possibility, there is also the possibility that this signal could be split-phased without pedestrian protection.  This means that the northbound traffic and southbound traffic have greens at separate phases of the cycle, yet pedestrians face walk during both parts of the NB and SB phases.  So if you make a left turn, you will not need to yield to on-coming traffic, but you should still yield to the pedestrians.

Having lived in CA, I find it odd that they would ever allow a permissive double left, so it would be nice if someone has seen this signal in action.

If you look at the GSV link I posted (first one from 2008), you can see both directions green at the same time. And, that was before the installation of the pictured "YIELD ON GREEN" signs, which seems to have occurred only recently. So all things point to this being a permissive double left turn.

Nevertheless, it is indeed very possible that it now operates with split phasing, despite the signage and prior street view images. But that seems less likely given the available evidence.

You may be right.  I generally do not like split-phasing, since it usually causes a lot of signal delay, but in a case where two private drive ways face each other, split-phasing works well.

Also, between 2008 and today, based only on GSV since I haven't been on this street, the city painted skip lines to mark the left turns as well as putting on the left turn yield on green signage.  Perhaps in 2008, the private company simply painted the arrows they wanted without checking into the proper state traffic application.  The authorities seem to have caught on, and made accommodations for it with the skip lines and the signage.  Whether this also means that they adjusted the signal timing is an open question that can  only be verified with someone driving by and observing it.

THe pedestrian crossing also complicates things and probably is what is preventing the installation of left turn arrows.


jakeroot

Found another one in British Columbia (bcroadguy). Another proper one...no option lanes, no one-way streets. Just a regular four-way signal:

Westminster Highway to southbound Nelson Road (Street View)

I think it's in Richmond, but it looks like a provincial install (modified in 2011 with the new ramps from Hwy 91). Interestingly, it was only built in 2016. Certainly one of the newest double permissive left turns that I know of. Many are quite old. There is a protected left turn signal that was installed for the opposing single-lane left turn, but it has been bagged for about 4 years now, with the turn remaining as fully permissive.

I've modified the below photo with dashed black lines, to show that the truck with the red trailer isn't going straight.


Amtrakprod

Roadgeek, railfan, and crossing signal fan. From Massachusetts, and in high school. Youtube is my website link. Loves FYAs signals. Interest in Bicycle Infrastructure. Owns one Leotech Pedestrian Signal, and a Safetran Type 1 E bell.

MNHighwayMan

Quote from: Amtrakprod on June 08, 2019, 07:37:32 PM
https://www.google.com/maps/@44.8568317,-93.2432461,3a,75y,342.6h,83.19t/data=!3m6!1e1!3m4!1sjAmxiFpEG17jHa_ZkhIRtA!2e0!7i13312!8i6656
Many of these in Bloomington MN

Did you actually see any of them operate with the FYA though? I've noticed that MnDOT/other Minnesota agencies like to install double FYA left signal heads, but these heads never actually operate with the FYA–only in protected mode.

jakeroot

I noticed those exact signals last time I was in Minneapolis. I thought the idea was to operate them in permissive mode during off-hours, but there's scant evidence of this being true.

mrsman

What's really odd is that there are signs on the cross street mentioning the FYA is to yield to opposing traffic.  The lack of such signs on the main street leads me to believe that they probably don't allow for the FYA to actually cycle.


mrsman

#206
As I was GSVing around the DC area to come up with some examples for another thread, I came across this intersection.

I don't know if 1.5 lanes counts for your critera, but here is a case with left lane turning left and second lane allowing the option to turn left or go straight.  In most cases, such a signal would be signalized with split-phasing, which is a special case of protected only lead-lag phasing where the opposing directions do not overlap at all.

In this case, the signal allow for permissive left turns.  During afternoon rush hour, a lagging left arrow comes up at the end of the cycle.  To prevent yellow trap, electronic "No left turn" signs are illuminated in the opposite direction during those times.  I don't believe the arrow comes up at all outside of rush hour.

12th and Independence SW.  The left turn leads towards the 14th Street bridge to Virginia.  (No left turn allowed from Independence to 14th, so drivers take Independence to 12th to C to 14th.)

https://www.google.com/maps/@38.8876192,-77.0274115,3a,75y,276.43h,65.49t/data=!3m6!1e1!3m4!1s1WXyRW6UOqHw3btPpy1ZHg!2e0!7i16384!8i8192


jakeroot

#207
Quote from: mrsman on July 25, 2019, 09:15:27 PM
As I was GSVing around the DC area to come up with some examples for another thread, I came across this intersection.

I don't know if 1.5 lanes counts for your critera, but here is a case with left lane turning left and second lane allowing the option to turn left or go straight.  In most cases, such a signal would be signalized with split-phasing, which is a special case of protected only lead-lag phasing where the opposing directions do not overlap at all.

In this case, the signal allow for permissive left turns.  During afternoon rush hour, a lagging left arrow comes up at the end of the cycle.  To prevent yellow trap, electronic "No left turn" signs are illuminated in the opposite direction during those times.  I don't believe the arrow comes up at all outside of rush hour.

12th and Independence SW.  The left turn leads towards the 14th Street bridge to Virginia.  (No left turn allowed from Independence to 14th, so drivers take Independence to 12th to C to 14th.)

https://www.google.com/maps/@38.8876192,-77.0274115,3a,75y,276.43h,65.49t/data=!3m6!1e1!3m4!1s1WXyRW6UOqHw3btPpy1ZHg!2e0!7i16384!8i8192

Very familiar with this intersection! My mother makes that left turn every day on her way home from work. I don't know why I didn't post about it before.

I took a video of the intersection a month ago. Very messy intersection.

https://youtu.be/x5RbNLwuoqc

There's another North of the Capitol. Louisiana @ New Jersey (NW).

jakeroot

Managed to find another, this one in Lakewood, WA (and probably the only one ever in Lakewood), although the whole intersection was rebuilt around 2013 and it was removed in favor of split-phasing.

Approaching South Tacoma Way from 84 St S, the left turns (which also featured a straight-on option lane) operated as fully permissive, opposite a driveway that I'm sure was lightly used.

https://goo.gl/maps/Q493n5J1BnZ4WRbJ6


mrsman

Here's one that I just discovered on my recent NYC trip a few days ago:

https://www.google.com/maps/@40.6101192,-73.9222153,3a,75y,201.3h,78.86t/data=!3m6!1e1!3m4!1sSyD5M_GVBc69m-5QgG_hIg!2e0!7i16384!8i8192

Ave U / Flatbush in Brooklyn.

While it's technically double permissive, it is so busy most of the time that most people will not be able to turn without the arrow anyway.

jakeroot

Quote from: mrsman on August 15, 2019, 04:58:06 PM
Here's one that I just discovered on my recent NYC trip a few days ago:

https://www.google.com/maps/@40.6101192,-73.9222153,3a,75y,201.3h,78.86t/data=!3m6!1e1!3m4!1sSyD5M_GVBc69m-5QgG_hIg!2e0!7i16384!8i8192

Ave U / Flatbush in Brooklyn.

While it's technically double permissive, it is so busy most of the time that most people will not be able to turn without the arrow anyway.

Nice find! NYC seems to have more of these than one might think. Flatbush apparently has at least two (also at Tillary).

mrsman

Quote from: jakeroot on August 16, 2019, 02:28:47 AM
Quote from: mrsman on August 15, 2019, 04:58:06 PM
Here's one that I just discovered on my recent NYC trip a few days ago:

https://www.google.com/maps/@40.6101192,-73.9222153,3a,75y,201.3h,78.86t/data=!3m6!1e1!3m4!1sSyD5M_GVBc69m-5QgG_hIg!2e0!7i16384!8i8192

Ave U / Flatbush in Brooklyn.

While it's technically double permissive, it is so busy most of the time that most people will not be able to turn without the arrow anyway.

That's true, but so far the other NYC examples mentioned above tend to be in places where the opposing left is prohibited for some reason (usually because of a one-way street).  A permissive double left is generally easier to implement when the opposing left is prohibited, as cars making the opposing left tend to block the clear view of the oncoming traffic.  [It also allowes for lagging lefts without worry of yellow trap, which tends to be beneficial, especially if one of the left turn lanes is an option lane.]


The interesting thing about Ave U turning onto Flatbush is that both directions can turn PPLT (and the westbound left is double lane).  I believe this is unique in NYC.

Nice find! NYC seems to have more of these than one might think. Flatbush apparently has at least two (also at Tillary).

jakeroot

Quote from: mrsman on August 16, 2019, 03:57:32 PM
Quote from: jakeroot on August 16, 2019, 02:28:47 AM
Nice find! NYC seems to have more of these than one might think. Flatbush apparently has at least two (also at Tillary).

That's true, but so far the other NYC examples mentioned above tend to be in places where the opposing left is prohibited for some reason (usually because of a one-way street).  A permissive double left is generally easier to implement when the opposing left is prohibited, as cars making the opposing left tend to block the clear view of the oncoming traffic.  [It also allowes for lagging lefts without worry of yellow trap, which tends to be beneficial, especially if one of the left turn lanes is an option lane.]

This is also true. But even with that in mind, many locales still tend to use protected-only phasing for all double left turns, irrespective of the individual characteristics of a particular intersection (which may or may not allow its implementation given any potential hazards). What impresses me about New York (the city? Surrounding counties?) is that they don't outright ban the installation of these types of setups. Many individual cities in the country don't ban them (opposite the situation of many state DOTs, which do ban the practice), but New York is impressive in that they have quite a few, which is more than I can say about most cities.

Amtrakprod

Quote from: mrsman on August 15, 2019, 04:58:06 PM
Here's one that I just discovered on my recent NYC trip a few days ago:

https://www.google.com/maps/@40.6101192,-73.9222153,3a,75y,201.3h,78.86t/data=!3m6!1e1!3m4!1sSyD5M_GVBc69m-5QgG_hIg!2e0!7i16384!8i8192

Ave U / Flatbush in Brooklyn.

While it's technically double permissive, it is so busy most of the time that most people will not be able to turn without the arrow anyway.
I honestly think New York State might rank last in traffic signals


iPhone
Roadgeek, railfan, and crossing signal fan. From Massachusetts, and in high school. Youtube is my website link. Loves FYAs signals. Interest in Bicycle Infrastructure. Owns one Leotech Pedestrian Signal, and a Safetran Type 1 E bell.

jakeroot

Quote from: Amtrakprod on August 18, 2019, 10:48:55 AM
I honestly think New York State might rank last in traffic signals

In terms of what? The intersection that mrsman linked to is pretty comprehensive, and the signals are very visible. Hell of a lot better than some other places.

steviep24

Quote from: Amtrakprod on August 18, 2019, 10:48:55 AM
Quote from: mrsman on August 15, 2019, 04:58:06 PM
Here's one that I just discovered on my recent NYC trip a few days ago:

https://www.google.com/maps/@40.6101192,-73.9222153,3a,75y,201.3h,78.86t/data=!3m6!1e1!3m4!1sSyD5M_GVBc69m-5QgG_hIg!2e0!7i16384!8i8192

Ave U / Flatbush in Brooklyn.

While it's technically double permissive, it is so busy most of the time that most people will not be able to turn without the arrow anyway.
I honestly think New York State might rank last in traffic signals


iPhone
New York City certainly does things differently than NYSDOT (or anywhere else for that matter but the signals linked above are not that bad.

Rothman

I'd like to hear more about how NYSDOT ranks last in signals.
Please note: All comments here represent my own personal opinion and do not reflect the official position(s) of NYSDOT.

Revive 755

Quote from: jakeroot on August 18, 2019, 03:01:27 PM
Quote from: Amtrakprod on August 18, 2019, 10:48:55 AM
I honestly think New York State might rank last in traffic signals

In terms of what? The intersection that mrsman linked to is pretty comprehensive, and the signals are very visible. Hell of a lot better than some other places.

For the linked photo at Flatbrush and Avenue U:
* No backplates on any heads.
* Given the number of lanes and amount traffic, IMHO all of the far side indications need to be 12".
* The 12" arrows next to 8" circular indications in a cluster/offset configuration doesn't look right.  If these are not outright non-MUTCD compliant they are certainly pushing the limits.
* There are not any heads directly over the roadway on Avenue U - only off to the side heads.  Off to the side heads can be to hard to quickly find if the driver is busy with other tasks such as navigation.  I would be curious as to the number of red light violations for those legs and number of angle accidents for the intersection.
* I'm not seeing any visors on the pedestrian signals

Amtrakprod

Quote from: Rothman on August 18, 2019, 08:30:26 PM
I'd like to hear more about how NYSDOT ranks last in signals.
Maybe we should move this onto my ranking states by traffic lights topic, but there aren't enough signals per lanes, and no backplates. It's a sloppy set up.


iPhone
Roadgeek, railfan, and crossing signal fan. From Massachusetts, and in high school. Youtube is my website link. Loves FYAs signals. Interest in Bicycle Infrastructure. Owns one Leotech Pedestrian Signal, and a Safetran Type 1 E bell.

Amtrakprod

Quote from: Revive 755 on August 19, 2019, 06:29:23 PM
Quote from: jakeroot on August 18, 2019, 03:01:27 PM
Quote from: Amtrakprod on August 18, 2019, 10:48:55 AM
I honestly think New York State might rank last in traffic signals

In terms of what? The intersection that mrsman linked to is pretty comprehensive, and the signals are very visible. Hell of a lot better than some other places.

For the linked photo at Flatbrush and Avenue U:
* No backplates on any heads.
* Given the number of lanes and amount traffic, IMHO all of the far side indications need to be 12".
* The 12" arrows next to 8" circular indications in a cluster/offset configuration doesn't look right.  If these are not outright non-MUTCD compliant they are certainly pushing the limits.
* There are not any heads directly over the roadway on Avenue U - only off to the side heads.  Off to the side heads can be to hard to quickly find if the driver is busy with other tasks such as navigation.  I would be curious as to the number of red light violations for those legs and number of angle accidents for the intersection.
* I'm not seeing any visors on the pedestrian signals
Yep all of that


iPhone
Roadgeek, railfan, and crossing signal fan. From Massachusetts, and in high school. Youtube is my website link. Loves FYAs signals. Interest in Bicycle Infrastructure. Owns one Leotech Pedestrian Signal, and a Safetran Type 1 E bell.

jeffandnicole

Quote from: Revive 755 on August 19, 2019, 06:29:23 PM
Quote from: jakeroot on August 18, 2019, 03:01:27 PM
Quote from: Amtrakprod on August 18, 2019, 10:48:55 AM
I honestly think New York State might rank last in traffic signals

In terms of what? The intersection that mrsman linked to is pretty comprehensive, and the signals are very visible. Hell of a lot better than some other places.

For the linked photo at Flatbrush and Avenue U:
* No backplates on any heads.
* Given the number of lanes and amount traffic, IMHO all of the far side indications need to be 12".
* The 12" arrows next to 8" circular indications in a cluster/offset configuration doesn't look right.  If these are not outright non-MUTCD compliant they are certainly pushing the limits.
* There are not any heads directly over the roadway on Avenue U - only off to the side heads.  Off to the side heads can be to hard to quickly find if the driver is busy with other tasks such as navigation.  I would be curious as to the number of red light violations for those legs and number of angle accidents for the intersection.
* I'm not seeing any visors on the pedestrian signals

I don't know how many intersections with traffic lights there are in New York City, but you pretty much named every condition found at every intersection.

For that...

Backplates are never required.  When the speed limit is 45 mph or above, they should have them, but not shall have them.  Many intersections throughout the country don't have them.  I'd even go as far to say that the majority of traffic lights country-wide don't have them.

8" lights installed prior to the recent 12" standard in the MUTCD are explicitly permitted per the MUTCD to remain in place for the rest of their useful life.

There's nothing pushing the limits of the 12" arrows next to 8" lights.

No visors are required on pedestrian signals.

So, based on this example, everything found at this intersection confirmed to MUTCD requirements at the time of installation.  And as mentioned, this is pretty much a typical NYC setup, so I don't know why this intersection was specifically shown, as it's off-topic in regards to the thread.




RestrictOnTheHanger

FWIW a vast majority of NYC's signals were installed before the 2009 MUTCD came out. With new, replacement, or modified installations, they do adhere to some of the relevant standards. Those being 1 signal per lane, 12" signals on 30+mph roads, and FYAs.

jakeroot

#222
Quote from: Amtrakprod on August 21, 2019, 06:43:26 AM
Quote from: Rothman on August 18, 2019, 08:30:26 PM
I'd like to hear more about how NYSDOT ranks last in signals.
Maybe we should move this onto my ranking states by traffic lights topic, but there aren't enough signals per lanes, and no backplates. It's a sloppy set up.

There's four signals and four approach lanes, and many places don't use backplates. Plus, unlike many agencies, they've managed to balance the signals so that you can see at least one no matter where you are sitting. Many states put every signal directly across from the stop line. That is deficient for everyone except those at the front of the line.

Keep in mind that you proclaimed NYS as being "last" in traffic signals. I'm not here to pretend that NYC is the best in the business, but you're not identifying things that would make, at least the city, rank last.

Quote from: Revive 755 on August 19, 2019, 06:29:23 PM
For the linked photo at Flatbrush and Avenue U:
* No backplates on any heads.
* Given the number of lanes and amount traffic, IMHO all of the far side indications need to be 12".
* The 12" arrows next to 8" circular indications in a cluster/offset configuration doesn't look right.  If these are not outright non-MUTCD compliant they are certainly pushing the limits.
* There are not any heads directly over the roadway on Avenue U - only off to the side heads.  Off to the side heads can be to hard to quickly find if the driver is busy with other tasks such as navigation.  I would be curious as to the number of red light violations for those legs and number of angle accidents for the intersection.
* I'm not seeing any visors on the pedestrian signals

* Backplates are nice, but it's unfair to hold it against NYC as many other places don't use them.
* 12-inch primary signals are probably wise overhead, but I don't think it's always necessary for secondary signals.
* 12-inch arrows next to 8-inch orbs were very common for a while. Still the norm in British Columbia (new, unactivated signals in that link). I don't see why this is a problem.
* Overhead signals are easily hidden by larger vehicles. Better to have a mix of both, kind of like the approach from Flatbush.
* As J&N indicates, pedestrian signal visors are not required. Most of the west coast does not use pedestrian signal visors (although I do like them).

I'm not going to pretend like this setup is the best in the world. There are certainly some things that I would change (adding a far-side overhead signal with a backplate, adding a right-side near-side signal, and adding a backplate to the tower signal on the far side), but NYC's traditional setups should not "rank last".

Now, what should rank last (IMO)? This is a great example (near Graham, WA) (this is not far from where I grew up, so I can assure you there is no bias). This is a 55-mph approach. If you are behind a tall vehicle, there's a decent chance that you cannot see the signals for a good portion of the approach. None of the BS you mentioned above (backplates, indication size, etc) matters if you can't even see a signal. This is why, IMO, NYC is actually a fair bit better than NYS, and many other states. At least the city doesn't put all their eggs in one basket (all the time at least).

jeffandnicole

Quote from: RestrictOnTheHanger on August 21, 2019, 08:50:47 AM
FWIW a vast majority of NYC's signals were installed before the 2009 MUTCD came out. With new, replacement, or modified installations, they do adhere to some of the relevant standards. Those being 1 signal per lane, 12" signals on 30+mph roads, and FYAs.

FYAs are optional, not standard.  Some states don't have a single FYA installed.

kphoger

Quote from: jakeroot on August 21, 2019, 02:45:33 PM
Now, what should rank last (IMO)? This is a great example (near Graham, WA) (this is not far from where I grew up, so I can assure you there is no bias). This is a 55-mph approach. If you are behind a tall vehicle, there's a decent chance that you cannot see the signals for a good portion of the approach. None of the BS you mentioned above (backplates, indication size, etc) matters if you can't even see a signal.

The worst I've personally driven through is this example in Coahuila.  A single overhead signal for each direction of a four-lane divided federal highway with very heavy commercial traffic.
Keep right except to pass.  Yes.  You.
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