Double left turns with permissive phasing

[mrsman]

Here's a dual permissive left in Brooklyn, NY (a state with very few dual permissive lefts). The left turn signal is a traditional 5-section tower (common in NYC? I'm not sure):

Flatbush @ Tillary, Brooklyn

The 5-section is the standard permissive signal in New York City. Another type is a 2-section 12" arrow face alongside a 3-section 8" face. I don't think there's a single doghouse inside the City.

Having family nearby until relatively recently, this was the only dual-permissive left turn installation I knew of anywhere until I was almost 9. It's still one of the less than 5 I have seen in person. I'm convinced that this was only done because opposing turns are prohibited and sightlines are wide-open. I do NOT know of another dual permissive left in New York that has opposing left turns (excluding the east end of Queens Blvd, which has open sightlines due to the way the WB ROW shifts).

There's a permissive dual option lane in NYC at Centre and Chambers on the Manhattan side off the Brooklyn Bridge:

https://www.google.com/maps/@40.7129151,-74.0042291,3a,75y,50.72h,79.23t/data=!3m6!1e1!3m4!1s5-CrH0LbXNFXaQhzIN7_nA!2e0!7i13312!8i6656

[RestrictOnTheHanger]

Here's a dual permissive left in Brooklyn, NY (a state with very few dual permissive lefts). The left turn signal is a traditional 5-section tower (common in NYC? I'm not sure):

Flatbush @ Tillary, Brooklyn

The 5-section is the standard permissive signal in New York City. Another type is a 2-section 12" arrow face alongside a 3-section 8" face. I don't think there's a single doghouse inside the City.

Having family nearby until relatively recently, this was the only dual-permissive left turn installation I knew of anywhere until I was almost 9. It's still one of the less than 5 I have seen in person. I'm convinced that this was only done because opposing turns are prohibited and sightlines are wide-open. I do NOT know of another dual permissive left in New York that has opposing left turns (excluding the east end of Queens Blvd, which has open sightlines due to the way the WB ROW shifts).

There's a permissive dual option lane in NYC at Centre and Chambers on the Manhattan side off the Brooklyn Bridge:

https://www.google.com/maps/@40.7129151,-74.0042291,3a,75y,50.72h,79.23t/data=!3m6!1e1!3m4!1s5-CrH0LbXNFXaQhzIN7_nA!2e0!7i13312!8i6656

This is the only doghouse proper in NYC (excluding the airports which have signals maintained by PANYNJ), which also happens to be one of the few spanwire signals in NYC

Arthur Kill Rd, Staten Island

https://goo.gl/maps/6UPjSZra8nv



This setup by Queens Center Mall is technically a dual permissive left, but left is the only way to go here. The signal sequence is

Red ball Green arrow  -> Red ball Yellow arrow -> red ball -> green ball (opposing traffic gets a green and pedestrians get walk signs) -> yellow ball in both directions -> red ball in both directions

Flashing yellow arrows would do better here IMO since drivers must yield on the green ball phase and there is high pedestrian and opposing traffic.



There are also quite a few permissive left turn / left turn+thru option lane setups in NYC. Two that i know of are 108 st/ LIE service road (lagging left in both directions, lanes are a bit hard to see in streetview), and Junction Blvd s/b at the LIE (lagging left)

[US 89]

I have never seen a dual permissive left in Utah, I think the state MUTCD bans them (but I could be wrong). I think they are a bad idea, because it makes for even more things to keep track of, and usually these intersections are already dangerous.

As for which permissive signal is used, FYA is used on newer lights around here, doghouses on older ones. I can think of only a couple 5-section verticals, which are usually ground-mounted (400 W and 200 S in SLC comes to mind).

EDIT: Although it is for a right turn, there's a 5-section head at St George Blvd and Bluff St in St George, Utah, mounted on the mast arm.

[jakeroot]

Riiga, this may interest you more than me. Here's a double permissive left turn in Denmark. Cruising around Denmark, they appear to have more than a few of these. There's none in Sweden, right?

The best part of this is that I'm predominantly Danish (my Great Great Grandmother emigrated from Denmark). Double permissive lefts run in my blood!

Street View: https://goo.gl/ZVmRpX (Røde Mellemvej @ Vejlands Allé, südlich von Kopenhagen)

[riiga]

Riiga, this may interest you more than me. Here's a double permissive left turn in Denmark. Cruising around Denmark, they appear to have more than a few of these. There's none in Sweden, right?

Very interesting, typically I associate Denmark with separated protected left turns, like this or this (semi-protected). I've dubbed them "Danish turn lane" due to their tendency to separate them by wide paint or a barrier, something I rarely see in Sweden.

As for as I know, there are no dual permissive left turns in Sweden. At speeds >50 km/h signal regulated permissive turns are not allowed, but must use a left turn arrow instead, and dual turn lanes are quite uncommon in cities, and when they exist I'm pretty sure they're all protected turns. I've come across some regulations related to left turns, but it seems the closest we have to permissive left turns are dual left turns using circular lights with no oncoming traffic. Translated below for reference.

[jakeroot]

Riiga, this may interest you more than me. Here's a double permissive left turn in Denmark. Cruising around Denmark, they appear to have more than a few of these. There's none in Sweden, right?

Very interesting, typically I associate Denmark with separated protected left turns, like this or this (semi-protected). I've dubbed them "Danish turn lane" due to their tendency to separate them by wide paint or a barrier, something I rarely see in Sweden.

I also noticed this while browsing around. In particular, the primary roads have left turn lanes separated by either a barrier or paint, but the side roads have everything smushed together (with a barrier only between opposing directions), like in the image above. I wasn't able to find any double permissive turns from a primary road, but several from a side street (that would otherwise have a yield sign). Here's one with a option lane: https://goo.gl/gTNQ7n (no visible red arrow signals, so I assume it's a permissive left).

As for as I know, there are no dual permissive left turns in Sweden. At speeds >50 km/h signal regulated permissive turns are not allowed, but must use a left turn arrow instead, and dual turn lanes are quite uncommon in cities, and when they exist I'm pretty sure they're all protected turns. I've come across some regulations related to left turns, but it seems the closest we have to permissive left turns are dual left turns using circular lights with no oncoming traffic. Translated below for reference.

http://i.imgur.com/hoUE0uZ.png

Dual turn lanes are also uncommon in the UK. Seems like older places just don't have the room for them.

So it looks like "split phasing" is used at these option-lane left turns?

Interesting that 50 km/h is the maximum for permissive lefts. Some states have limits on permissive lefts (usually speed limit ≤ 70 km/h), but I'm unaware of a state with a 50 km/h limit (though that's just for the state -- individual cities are free to do as they wish). 50 km/h seems kind of low to me.

Aviation Parkway in Tucson, Arizona is a 90 km/h road with permissive lefts: https://goo.gl/KxGp3E. Very few roads with this high of a limit have signals in the US, so this must be one of the highest posted roads with permissive lefts.

[cl94]

Riiga, this may interest you more than me. Here's a double permissive left turn in Denmark. Cruising around Denmark, they appear to have more than a few of these. There's none in Sweden, right?

Very interesting, typically I associate Denmark with separated protected left turns, like this or this (semi-protected). I've dubbed them "Danish turn lane" due to their tendency to separate them by wide paint or a barrier, something I rarely see in Sweden.

I also noticed this while browsing around. In particular, the primary roads have left turn lanes separated by either a barrier or paint, but the side roads have everything smushed together (with a barrier only between opposing directions), like in the image above. I wasn't able to find any double permissive turns from a primary road, but several from a side street (that would otherwise have a yield sign). Here's one with a option lane: https://goo.gl/gTNQ7n (no visible red arrow signals, so I assume it's a permissive left).

As for as I know, there are no dual permissive left turns in Sweden. At speeds >50 km/h signal regulated permissive turns are not allowed, but must use a left turn arrow instead, and dual turn lanes are quite uncommon in cities, and when they exist I'm pretty sure they're all protected turns. I've come across some regulations related to left turns, but it seems the closest we have to permissive left turns are dual left turns using circular lights with no oncoming traffic. Translated below for reference.

http://i.imgur.com/hoUE0uZ.png

Dual turn lanes are also uncommon in the UK. Seems like older places just don't have the room for them.

So it looks like "split phasing" is used at these option-lane left turns?

Interesting that 50 km/h is the maximum for permissive lefts. Some states have limits on permissive lefts (usually speed limit ≤ 70 km/h), but I'm unaware of a state with a 50 km/h limit (though that's just for the state -- individual cities are free to do as they wish). 50 km/h seems kind of low to me.

Aviation Parkway in Tucson, Arizona is a 90 km/h road with permissive lefts: https://goo.gl/KxGp3E. Very few roads with this high of a limit have signals in the US, so this must be one of the highest posted roads with permissive lefts.

I wouldn't say it's uncommon to see signals or permissive lefts on a road posted at 55 mph (90 km/h), definitely not in the northeast and midwest. Ohio allows signalized at-grades on roads posted up to 60 (mostly protected, but I have seen a couple permissive) and unsignalized at-grades up to 70. New Jersey divided highways are often 55, signals or "Jersey Freeway". Default for New York is 55 (co-posted as 90 km/h in a couple places) and it doesn't go down for signals. NY's 55 roads generally have permissive lefts.

[jakeroot]

As for as I know, there are no dual permissive left turns in Sweden. At speeds >50 km/h signal regulated permissive turns are not allowed, but must use a left turn arrow instead, and dual turn lanes are quite uncommon in cities, and when they exist I'm pretty sure they're all protected turns. I've come across some regulations related to left turns, but it seems the closest we have to permissive left turns are dual left turns using circular lights with no oncoming traffic. Translated below for reference.

http://i.imgur.com/hoUE0uZ.png

Dual turn lanes are also uncommon in the UK. Seems like older places just don't have the room for them.

So it looks like "split phasing" is used at these option-lane left turns?

Interesting that 50 km/h is the maximum for permissive lefts. Some states have limits on permissive lefts (usually speed limit ≤ 70 km/h), but I'm unaware of a state with a 50 km/h limit (though that's just for the state -- individual cities are free to do as they wish). 50 km/h seems kind of low to me.

Aviation Parkway in Tucson, Arizona is a 90 km/h road with permissive lefts: https://goo.gl/KxGp3E. Very few roads with this high of a limit have signals in the US, so this must be one of the highest posted roads with permissive lefts.

I wouldn't say it's uncommon to see signals or permissive lefts on a road posted at 55 mph (90 km/h), definitely not in the northeast and midwest. Ohio allows signalized at-grades on roads posted up to 60 (mostly protected, but I have seen a couple permissive) and unsignalized at-grades up to 70. New Jersey divided highways are often 55, signals or "Jersey Freeway". Default for New York is 55 (co-posted as 90 km/h in a couple places) and it doesn't go down for signals. NY's 55 roads generally have permissive lefts.

After doing a bit of research, it appears that my comment was (a bit) unfounded. Even Washington has several high speed roads with permissive lefts. I guess I forgot about them.

[US 89]

As for as I know, there are no dual permissive left turns in Sweden. At speeds >50 km/h signal regulated permissive turns are not allowed, but must use a left turn arrow instead, and dual turn lanes are quite uncommon in cities, and when they exist I'm pretty sure they're all protected turns. I've come across some regulations related to left turns, but it seems the closest we have to permissive left turns are dual left turns using circular lights with no oncoming traffic. Translated below for reference.

http://i.imgur.com/hoUE0uZ.png

Dual turn lanes are also uncommon in the UK. Seems like older places just don't have the room for them.

So it looks like "split phasing" is used at these option-lane left turns?

Interesting that 50 km/h is the maximum for permissive lefts. Some states have limits on permissive lefts (usually speed limit ≤ 70 km/h), but I'm unaware of a state with a 50 km/h limit (though that's just for the state -- individual cities are free to do as they wish). 50 km/h seems kind of low to me.

Aviation Parkway in Tucson, Arizona is a 90 km/h road with permissive lefts: https://goo.gl/KxGp3E. Very few roads with this high of a limit have signals in the US, so this must be one of the highest posted roads with permissive lefts.

I wouldn't say it's uncommon to see signals or permissive lefts on a road posted at 55 mph (90 km/h), definitely not in the northeast and midwest. Ohio allows signalized at-grades on roads posted up to 60 (mostly protected, but I have seen a couple permissive) and unsignalized at-grades up to 70. New Jersey divided highways are often 55, signals or "Jersey Freeway". Default for New York is 55 (co-posted as 90 km/h in a couple places) and it doesn't go down for signals. NY's 55 roads generally have permissive lefts.

After doing a bit of research, it appears that my comment was (a bit) unfounded. Even Washington has several high speed roads with permissive lefts. I guess I forgot about them.

In Utah, a protected left is required if the speed limit is 60 or higher, and protected lefts are required for dual left turn lanes. https://www.udot.utah.gov/main/uconowner.gf?n=22168023889671869

[riiga]

Here's one with a option lane: https://goo.gl/gTNQ7n (no visible red arrow signals, so I assume it's a permissive left).

Indeed, looks like a permissive left setup with a short protected phase (the lower left signal has an extra light for the green arrow).

So it looks like "split phasing" is used at these option-lane left turns?

Most probably. Never seen one of them in real life though, only single permissive lefts.

Interesting that 50 km/h is the maximum for permissive lefts. Some states have limits on permissive lefts (usually speed limit ≤ 70 km/h), but I'm unaware of a state with a 50 km/h limit (though that's just for the state -- individual cities are free to do as they wish). 50 km/h seems kind of low to me.

Well, we don't allow signals at all above 70 km/h, so I think it makes sense to keep permissive turns to city traffic (where you would expect a 50 km/h limit). Permissive turns at >60 km/h also seems like a great way to cause accidents. 

Outside of cities we tend to favor this type of offset junction. Traffic volumes are rarely a problem here, so signals outside of city limits are very rare. I know of one that sort of counts, now replaced by a roundabout.

[jakeroot]

[W]e don't allow signals at all above 70 km/h, so I think it makes sense to keep permissive turns to city traffic (where you would expect a 50 km/h limit). Permissive turns at >60 km/h also seems like a great way to cause accidents.

I've seen studies that show permissive signals to be safer than protected-only signals, because drivers are less impatient. A city near me (Federal Way, WA) recently switched all their protected lefts for protected/permissive lefts, and they saw a marked drop in collisions. People weren't "pushing the lights" like they were before.

Outside of cities we tend to favor this type of offset junction. Traffic volumes are rarely a problem here, so signals outside of city limits are very rare. I know of one that sort of counts, now replaced by a roundabout.

Rural areas are certainly no place for signals (lest it's a very busy road and no money exists for grade-separation). Offset junctions are decidedly rare in the US (mostly due to rural roads being plotted in exactly straight lines), but they should be more common. It makes it way easier to cross a busy highway, and is almost certainly safer than having to look both ways and flooring it.

[Brian556]

Here's a FYA dual left turn on Sandy Lake Rd at Denton Tap Rd in Coppell, TX:

[jakeroot]

I'm glad to see them pop up, but I really wish the turns (^^ above) had a positive offset, a la Wisconsin or Tucson. The ones above have a negative offset, which creates rather poor visibility. You can still maintain a median between directions, just perhaps a smaller one.

I only suggest having positive offset because the double permissive leader, Tucson, suggests it, and their's seem to operate remarkably well, given the high volumes of traffic on their arterial roads.

[Brian556]

Quote from jakeroot:

I'm glad to see them pop up, but I really wish the turns (^^ above) had a positive offset, a la Wisconsin or Tucson. The ones above have a negative offset, which creates rather poor visibility. You can still maintain a median between directions, just perhaps a smaller one.

I only suggest having positive offset because the double permissive leader, Tucson, suggests it, and their's seem to operate remarkably well, given the high volumes of traffic on their arterial roads.

Heck, around here, most divided highway left turns have crappy visibility if the oncoming turn lane is occupied. Never mind a double turn.
This is in front of my neighborhood, and tis the worst one in our area:




Its awkward when the FYA's are installed because they also change the operation of the signals, allowing a permissive left while the oncoming traffic has a green ball and green arrow.

[roadfro]

Its awkward when the FYA's are installed because they also change the operation of the signals, allowing a permissive left while the oncoming traffic has a green ball and green arrow.

That's part of the point of FYA: FYA is tied to the opposing green (instead of the adjacent green), providing greater efficiency by allowing permissive turns in more situations than a standard doghouse.

[jakeroot]

Heck, around here, most divided highway left turns have crappy visibility if the oncoming turn lane is occupied. Never mind a double turn.
This is in front of my neighborhood, and tis the worst one in our area:

http://i1209.photobucket.com/albums/cc395/Brian5561/6242014024_zps0f2f29f1.jpg

Those types of left turns (negative offset, like in your image) are the ones that especially need waiting lines (dotted lines in the road that indicate where drivers should wait for oncoming traffic) (examples provided below). People typically pull straight out into the intersection when waiting to turn left. This is not good for visibility*. Optimal visibility (with negative offset left turns) is at the point when you are physically closest to oncoming traffic. Positioning your hood to be nearly on the left edge of the left lane of oncoming traffic sounds like a bad idea, but visibility is exceptionally good at this angle. If you watch any dash cam footage from places like the UK, Japan, or South Africa (both which have a lot of permissive turns), you'll see that this is where they wait.

Here are some examples of waiting lines (first from Japan, second from South Africa, third from Tucson). Note that all require waiting at an angle. The first two examples are standard road markings in those countries:







*This method of turning left originated from the idea that sitting at an angle puts you in a position to get pushed into oncoming traffic when waiting to turn left, in the event of a rear-end crash. While I have no data that shows this to be a false theory, I've also never seen any data that shows it to be true (it seems to be based on an idea of what could happen, rather than something that actually has).

[US 89]

Heck, around here, most divided highway left turns have crappy visibility if the oncoming turn lane is occupied. Never mind a double turn.
This is in front of my neighborhood, and tis the worst one in our area:

http://i1209.photobucket.com/albums/cc395/Brian5561/6242014024_zps0f2f29f1.jpg

Those types of left turns (negative offset, like in your image) are the ones that especially need waiting lines (dotted lines in the road that indicate where drivers should wait for oncoming traffic) (examples provided below). People typically pull straight out into the intersection when waiting to turn left. This is not good for visibility*. Optimal visibility (with negative offset left turns) is at the point when you are physically closest to oncoming traffic. Positioning your hood to be nearly on the left edge of the left lane of oncoming traffic sounds like a bad idea, but visibility is exceptionally good at this angle. If you watch any dash cam footage from places like the UK, Japan, or South Africa (both which have a lot of permissive turns), you'll see that this is where they wait.

Here are some examples of waiting lines (first from Japan, second from South Africa, third from Tucson). Note that all require waiting at an angle. The first two examples are standard road markings in those countries:







*This method of turning left originated from the idea that sitting at an angle puts you in a position to get pushed into oncoming traffic when waiting to turn left, in the event of a rear-end crash. While I have no data that shows this to be a false theory, I've also never seen any data that shows it to be true (it seems to be based on an idea of what could happen, rather than something that actually has).

I have never heard of this, but it makes so much sense. I wish lines like those were standard practice in the US. There are several intersections around here where visibility is an issue.

However, there are a few problems I can see with this. One is that a lot of our roads don't have that wide median in the third photo, so there wouldn't necessarily be room to position yourself like that.

The other problem is that normally, if you slightly overshoot the stop line at a normal intersection, no big deal. If you misjudge or overshoot this line, you will almost certainly have a head on collision.

[jakeroot]

Heck, around here, most divided highway left turns have crappy visibility if the oncoming turn lane is occupied. Never mind a double turn.
This is in front of my neighborhood, and tis the worst one in our area:

http://i1209.photobucket.com/albums/cc395/Brian5561/6242014024_zps0f2f29f1.jpg

Those types of left turns (negative offset, like in your image) are the ones that especially need waiting lines (dotted lines in the road that indicate where drivers should wait for oncoming traffic) (examples provided below). People typically pull straight out into the intersection when waiting to turn left. This is not good for visibility*. Optimal visibility (with negative offset left turns) is at the point when you are physically closest to oncoming traffic. Positioning your hood to be nearly on the left edge of the left lane of oncoming traffic sounds like a bad idea, but visibility is exceptionally good at this angle. If you watch any dash cam footage from places like the UK, Japan, or South Africa (both which have a lot of permissive turns), you'll see that this is where they wait.

I have never heard of this, but it makes so much sense. I wish lines like those were standard practice in the US. There are several intersections around here where visibility is an issue.

As far as I know, the example from Tucson (the last image) is the only use of this type of line anywhere in the US. I haven't bothered to check with the head of traffic control in Tucson, but I'd really like to know where he got the idea (though I have some ideas, as you might imagine).

However, there are a few problems I can see with this. One is that a lot of our roads don't have that wide median in the third photo, so there wouldn't necessarily be room to position yourself like that....The other problem is that normally, if you slightly overshoot the stop line at a normal intersection, no big deal. If you misjudge or overshoot this line, you will almost certainly have a head on collision.

They wouldn't really be necessary when the turn lanes are pointed straight at each other, or when there was positive offset. Though in any case, they come in handy, especially when there's a double left yield (rare, but a waiting line to prevent the outer lane from blocking the inner lane's sightlines would be helpful). This was discussed up-thread.

The idea of "overshooting" the waiting line is possible, but turning straight into oncoming traffic is possible today even without the line. If anything, the line is a helpful reminder of, not only how far you can go without getting in the way of anyone, but also that the turn is a yield situation (unless there's an overriding signal). I suspect failure-to-give way collisions would actually drop after implementation, but I have no way of knowing for sure.

[jakeroot]

Just decided the check the poll.

Surprisingly close.

The real surprise? 15% of those polled, picked "cat".

wtf

[US 89]

Just decided the check the poll.

Surprisingly close.

The real surprise? 15% of those polled, picked "cat".

wtf

Does that mean there are 2 left turn lanes, but really there's only one because there's a cat sitting in one of them?

[jakeroot]

Just decided the check the poll.

Surprisingly close.

The real surprise? 15% of those polled, picked "cat".

wtf

Does that mean there are 2 left turn lanes, but really there's only one because there's a cat sitting in one of them?

[Revive 755]

Found a protected-permissive dual left in Ankeny, Iowa for US 69/Ankeny Boulvard at 1st Street that uses two five-section towers:  Streetview

The Des Moines newspaper though indicates this will be changed to a single left.  http://www.desmoinesregister.com/story/news/local/ankeny/2017/09/29/ankeny-boulevard-and-1st-street-improvements-coming-2020/718133001/

[MNHighwayMan]

Having been through that intersection a few times, yeah, it can be a bit hairy. I never understood the reason for there being two left turn lanes onto SB US-69 (Ankeny Blvd).

[jakeroot]

Doesn't look like a well-designed double left (the outer left turn appears to conflict with the opposing left). Nevermind the poor visibility. Can't blame them for switching to a single left setup. At least they aren't changing it to protected-only.

[jakeroot]

I grew up learning how to drive on the Gulf Coast in Mississippi, where there are apparently still at least three intersections with dual permissive lefts (which are at (1) Popps Ferry Rd and Cedar Lake Blvd in Biloxi, (2) MS 605 (Cowan Rd) and Pass Rd in Gulfport, and (3) WB Rodriguez St to SB I-110 in D'Iberville (see lane markings)).

Just an update. All three of the intersections you posted have been updated. Intersections one and two have been changed to protected only, whereas the third now has mast-arms with new signals (still doghouses for the double left, thank God).

In the first example, they widened Popps Ferry Road and changed the signal phasing. They could have easily aligned the WB left turn so that it was offset to the left (improving visibility for EB turning traffic). But, I guess they decided protected was good enough! Oh well.

Since then, I think the only other place I've seen them is Duluth, Minnesota, but since Minnesota is the place I think I've seen the most FYAs outside of Oregon and Washington, there are probably more lurking about.

Do you remember where this was? I've was looking at a map of Duluth, when I remembered this post. But I cannot find any dual permissive lefts in Duluth. I have seen quite a few dual FYA displays elsewhere in Minnesota IRL, but they all ran protected-only. Not sure what MnDOT policy is nowadays.