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

Amtrakprod

Quote from: jakeroot on April 13, 2016, 02:36:51 PM
Quote from: Jardine on April 13, 2016, 10:51:55 AM
Even with an obvious artillery cannon blowing up cars to deter folks attempting lane changing while dual left turning, and/or the folks dual left turning onto streets with more than 2 lanes and randomly going down whatever lane they want regardless of whether or not anyone is beside them on either side and they are also attempting a similar and non-compatible random lane selection themselves (all the while mowing down pedestrians) I'd say this is an extremely poor idea for places like Sarpy County Nebraska and Rockford Illinois.

This perceived danger (vehicles changing lanes during a turn) seems to be the biggest fear among those who oppose dual permissive turns. My thought is this: are vehicles changing lanes during the permissive phase more often than during the protected phase?




Visibility really should be the argument against dual permissive turns. From studying the various dual turn lanes around the world, I've come up with two solutions to this issue:

1) Offset the dual turn lanes whenever possible. This requires slightly more ROW, but the cities that use this style seem to report fewer issues. Tucson is the best example. Note the chevrons between the left turn lanes and the through lanes. The FHWA's "Signalized Intersections: Informational Guide" has a couple pages dedicated to Tucson's offset dual turns lanes, and notes a "potential issue is sight distance for the left-turning vehicles", and that "[t]he City of Tucson addresses this concern by offsetting the far lane by 1.2 to 1.5 m (4 to 5 ft) so that it has the same sight distance as a single left-turn lane" (PDF pg 338).



2) Use secondary stop lines. These are almost unheard of in the US. They seem to be used more often in Europe, but more important to this conversation, South Africa has several dual permissive turn lanes with these secondary stop lines. In cities with drivers who pull pretty far forward into the intersection (cool with a single turn lane, but a little annoying with two turn lanes), this helps prevent the inside lane from being totally blind. As well, cities with more hesitant drivers will be more apt to pull forward to wait to turn, which helps with throughput. Because this secondary stop line is more of a "yield line", I'd recommend using sharks teeth, instead of the broken white lines used in South Africa:




I have called those "yield boxes" , I really think they are very smart and should be used in the US


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.


MNHighwayMan

Quote from: jakeroot on December 24, 2018, 03:13:47 PM
From this 2018/August Street View image, it appears the intersection is now operating with single left turns: http://bit.ly/2T7xoVp

Quote from: MNHighwayMan on December 24, 2018, 04:20:45 PM
That might just be temporary for minor road repair, because that linked article stated that it was going to be a couple years before they removed it. I'll have to go check it out when I'm not tipsy from Christmas. ;-)

So it has been removed, I must report. All the old five-section left turn towers at the intersection were also replaced with FYAs.


jakeroot

Quote from: MNHighwayMan on December 26, 2018, 01:36:06 PM
Quote from: jakeroot on December 24, 2018, 03:13:47 PM
From this 2018/August Street View image, it appears the intersection is now operating with single left turns: http://bit.ly/2T7xoVp

Quote from: MNHighwayMan on December 24, 2018, 04:20:45 PM
That might just be temporary for minor road repair, because that linked article stated that it was going to be a couple years before they removed it. I'll have to go check it out when I'm not tipsy from Christmas. ;-)

So it has been removed, I must report. All the old five-section left turn towers at the intersection were also replaced with FYAs.[/img]

I feared as much. Thanks for the photos.

Is there a second flashing yellow arrow on the left side of the intersection? Just curious. I can't remember Iowa policy on auxiliary traffic lights.

MNHighwayMan

Quote from: jakeroot on December 26, 2018, 09:48:10 PM
Is there a second flashing yellow arrow on the left side of the intersection? Just curious. I can't remember Iowa policy on auxiliary traffic lights.

Nope.



Most of the time, in Iowa, there's just the overhead signal head. Rarely I'll see a left-hand arrow setup but I haven't seen any discernible reason for when and where they get applied.

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.

jakeroot

^^
CO probably has the most of any state. There are probably some jurisdictions that don't permit them and/or have not yet had a reason to use one, but they are all over the state in general.

jakeroot

Quote from: bcroadguy on November 15, 2018, 04:09:23 AM
I found one in Richmond, BC:

Found yet another in Richmond. Southbound Aviation at Grant McConachie Way.

http://bit.ly/2GXQFHK -- << street view shot from 2015

I think the intersection was formerly a single-lane left, but was changed to a dual left, though tire marks suggest it's always been a dual left turn (with an option lane).

Any idea if this still operates with permissive phasing? I'd check myself but have a swamped schedule down here in Seattle. No free days for a while.

roadfro

Quote from: jakeroot on January 08, 2019, 04:46:00 AM
Found yet another in Richmond. Southbound Aviation at Grant McConachie Way.

http://bit.ly/2GXQFHK -- << street view shot from 2015

I think the intersection was formerly a single-lane left, but was changed to a dual left, though tire marks suggest it's always been a dual left turn (with an option lane).

Any idea if this still operates with permissive phasing? I'd check myself but have a swamped schedule down here in Seattle. No free days for a while.

This street view from August 2018 seems to suggest it's operating in split phase.
Roadfro - AARoads Pacific Southwest moderator since 2010, Nevada roadgeek since 1983.

jakeroot

Quote from: roadfro on January 08, 2019, 09:47:49 AM
Quote from: jakeroot on January 08, 2019, 04:46:00 AM
Found yet another in Richmond. Southbound Aviation at Grant McConachie Way.

http://bit.ly/2GXQFHK -- << street view shot from 2015

I think the intersection was formerly a single-lane left, but was changed to a dual left, though tire marks suggest it's always been a dual left turn (with an option lane).

Any idea if this still operates with permissive phasing? I'd check myself but have a swamped schedule down here in Seattle. No free days for a while.

This street view from August 2018 seems to suggest it's operating in split phase.

It should be noted that Canada uses flashing green arrows during the protected phase at most lights. At least the ones in BC operate at 2 flashes per second, so they are not always picked up on camera. Since something like 90% of traffic lights in Vancouver operate with permissive phasing (very high understanding of yielding on green), something tells me that drivers in the street view images would not continue turning across traffic without a green arrow. I'm guessing we just can't see it.

Amtrakprod

Quote from: jakeroot on January 08, 2019, 11:25:02 AM
Quote from: roadfro on January 08, 2019, 09:47:49 AM
Quote from: jakeroot on January 08, 2019, 04:46:00 AM
Found yet another in Richmond. Southbound Aviation at Grant McConachie Way.

http://bit.ly/2GXQFHK -- << street view shot from 2015

I think the intersection was formerly a single-lane left, but was changed to a dual left, though tire marks suggest it's always been a dual left turn (with an option lane).

Any idea if this still operates with permissive phasing? I'd check myself but have a swamped schedule down here in Seattle. No free days for a while.

This street view from August 2018 seems to suggest it's operating in split phase.

It should be noted that Canada uses flashing green arrows during the protected phase at most lights. At least the ones in BC operate at 2 flashes per second, so they are not always picked up on camera. Since something like 90% of traffic lights in Vancouver operate with permissive phasing (very high understanding of yielding on green), something tells me that drivers in the street view images would not continue turning across traffic without a green arrow. I'm guessing we just can't see it.
If you go back a few paces, the green arrow is shown: https://www.google.com/maps/@49.1931255,-123.1668942,3a,23.2y,188.05h,93.98t/data=!3m6!1e1!3m4!1sFuJGq7hoHkLGO5qTS-1n4g!2e0!7i16384!8i8192
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

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 January 17, 2019, 04:02:54 PM
Found one in Indiana: https://www.google.com/maps/@38.9579252,-85.8625074,3a,71.9y,334.06h,73.84t/data=!3m6!1e1!3m4!1sjFSq9kYJFmwIV2so6GGPDQ!2e0!7i13312!8i6656

Cool, thanks for sharing! Interesting to note that the signals were replaced in or around 2016, so the local agency responsible for the signals must think they're working OK. Otherwise, I assume they would have removed them. Many of the signals first posted in this thread have been removed, probably for similar reasons (change of heart on the part of the responsible agency, I suspect).

Revive 755

There's a left plus left-thru-right at the Potomac Boulevard intersection with IL 15 in Mount Vernon just west of I-64/I-57 that appears to use permissive phasing.  Streetview.

jakeroot

Quote from: Revive 755 on January 18, 2019, 10:36:10 PM
There's a left plus left-thru-right at the Potomac Boulevard intersection with IL 15 in Mount Vernon just west of I-64/I-57 that appears to use permissive phasing.  Streetview.

Sure looks like it. The double "YIELD ON GREEN" signs seem to be the obvious giveaway, although I'd like to find some street view position that showed it in its permissive phase at some point (on mobile at the moment).

bcroadguy

Quote from: jakeroot on January 08, 2019, 11:25:02 AM
Quote from: roadfro on January 08, 2019, 09:47:49 AM
Quote from: jakeroot on January 08, 2019, 04:46:00 AM
Found yet another in Richmond. Southbound Aviation at Grant McConachie Way.

http://bit.ly/2GXQFHK -- << street view shot from 2015

I think the intersection was formerly a single-lane left, but was changed to a dual left, though tire marks suggest it's always been a dual left turn (with an option lane).

Any idea if this still operates with permissive phasing? I'd check myself but have a swamped schedule down here in Seattle. No free days for a while.

This street view from August 2018 seems to suggest it's operating in split phase.

It should be noted that Canada uses flashing green arrows during the protected phase at most lights. At least the ones in BC operate at 2 flashes per second, so they are not always picked up on camera. Since something like 90% of traffic lights in Vancouver operate with permissive phasing (very high understanding of yielding on green), something tells me that drivers in the street view images would not continue turning across traffic without a green arrow. I'm guessing we just can't see it.

It's almost definitely not split phase. All the double left split phase signals I've seen in BC use non-flashing arrows
(Examples: https://www.google.com/maps/@49.2329204,-122.8526462,3a,44y,187.49h,86.45t/data=!3m6!1e1!3m4!1sO1weXeBIgAFtF5WRu70vrA!2e0!7i13312!8i6656, https://www.google.com/maps/@49.2307959,-122.6894904,3a,19.9y,3.87h,90.51t/data=!3m6!1e1!3m4!1slFZVfZhYrRmC0fS_rG9B4w!2e0!7i13312!8i6656)
I think you found yourself a permissive double left :)

Amtrakprod

Never thought I would find this, and sadly it has been changed, but I found one in downtown Springfield MA:
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.

bcroadguy

Quote from: Amtrakprod on January 19, 2019, 11:51:54 AM
Never thought I would find this, and sadly it has been changed, but I found one in downtown Springfield MA:


I wonder what the top part of that signal does. It's weird how it has four lights but the bottom one is a solid green. Two reds for extra emphasis maybe?

Amtrakprod

Quote from: bcroadguy on January 21, 2019, 05:36:14 AM
Quote from: Amtrakprod on January 19, 2019, 11:51:54 AM
Never thought I would find this, and sadly it has been changed, but I found one in downtown Springfield MA:


I wonder what the top part of that signal does. It's weird how it has four lights but the bottom one is a solid green. Two reds for extra emphasis maybe?
Nope, sometimes MA just uses an extra section, I have no idea why :spin: :spin: :spin:
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

#193
^^
I'm guessing the second-to-bottom lens is unused, since that was the section that previously displayed a green orb. Not sure why they didn't just disable the bottom green arrow.

Either way, cool that a double left yield existed in Mass for a short time!

EDIT: I checked out the old intersection on Google Maps. The top two sections appear to have been red displays: the top was a red orb, and the second-to-top was a red arrow. I'm guessing the bottom two were a yellow orb or yellow arrow, and then a green arrow.

Amtrakprod

Quote from: jakeroot on January 21, 2019, 11:55:36 AM
^^
I'm guessing the second-to-bottom lens is unused, since that was the section that previously displayed a green orb. Not sure why they didn't just disable the bottom green arrow.

Either way, cool that a double left yield existed in Mass for a short time!

EDIT: I checked out the old intersection on Google Maps. The top two sections appear to have been red displays: the top was a red orb, and the second-to-top was a red arrow. I'm guessing the bottom two were a yellow orb or yellow arrow, and then a green arrow.
The unused section is the second to the top.
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 January 21, 2019, 02:14:24 PM
The unused section is the second to the top.

Is that the case now? In my Street View link, the second-to-top lens is still in use as a red left arrow.

Amtrakprod

Quote from: jakeroot on January 21, 2019, 03:31:45 PM
Quote from: Amtrakprod on January 21, 2019, 02:14:24 PM
The unused section is the second to the top.

Is that the case now? In my Street View link, the second-to-top lens is still in use as a red left arrow.
I'm pretty sure this left turn is illegal now, I'll check as I'm going to Springfield next weekend.
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

#197
I have located bigfoot...a signalized one in California. And it's in Santa Clara County, which is not exactly known for permissive phasing. The unsignalized one was in Cupertino at the Apple Headquarters, only a short walk away.

Agilent Technologies business estate @ Stevens Creek Blvd

(2008 GSV with green signals displayed (turn camera around)) (modern-day GSV with [Clearview] "YIELD ON GREEN" signs).

The signal was actually updated a few years ago, to move Steven Creek Blvd's median-mounted left turn signals overhead. Most other signals were replaced as well. Rather than putting in split-phasing, the engineer responsible instead decided to repaint the left turn guidance lines and install "YIELD ON GREEN" signs. So clearly, this install was not an accident.


mrsman

Quote from: jakeroot on April 07, 2019, 02:07:24 PM
I have located bigfoot...a signalized one in California. And it's in Santa Clara County, which is not exactly known for permissive phasing. The unsignalized one was in Cupertino at the Apple Headquarters, only a short walk away.

Agilent Technologies business estate @ Stevens Creek Blvd

(2008 GSV with green signals displayed (turn camera around)) (modern-day GSV with [Clearview] "YIELD ON GREEN" signs).

The signal was actually updated a few years ago, to move Steven Creek Blvd's median-mounted left turn signals overhead. Most other signals were replaced as well. Rather than putting in split-phasing, the engineer responsible instead decided to repaint the left turn guidance lines and install "YIELD ON GREEN" signs. So clearly, this install was not an accident.



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.

jakeroot

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.



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