Double left turns with permissive phasing

[jakeroot]

Would this count as a permissive double left turn? Found this in Brunswick ME driving back from Orono yesterday...

Maine Street to US-1 North on-ramp in Brunswick, Maine

Flashing red arrows for the double left turns, and flashing yellow balls for the thru directions. There is no stop bar at this intersection and the left turning drivers treat it like a flashing yellow arrow...

Ian also posted this example to the "Unsignalized Double Left Turns" thread.

Whether it's truly unsignalized or not, I don't know. But at any rate, it's definitely unusual. And I like it.

[kphoger]

But at any rate, it's definitely unusual. And therefore I like it.

Edited for accuracy.

[jakeroot]

Totally forgot to post this example that I found a few weeks ago:

Left turn from southbound Sarival Road to eastbound Northern Parkway, outside Waddell, Arizona.

There are a few other permissive double lefts in the Phoenix area, and most are fairly old. Excluding those in places like Chandler, where the permissive phase never seems to activate, these are quite new and are effectively in permissive mode 100% of the time. I'm sure Maricopa County would install fully-protected left turns once Sarival Road is fully widened, and the Parkway's easterly extension is complete. But they probably realized how quiet the area would be until such point, so they installed five-section towers until then. Well done, Maricopa County.

[jakeroot]

But at any rate, it's definitely unusual. And therefore I like it.

Edited for accuracy.

[roadfro]

Totally forgot to post this example that I found a few weeks ago:

Left turn from southbound Sarival Road to eastbound Northern Parkway, outside Waddell, Arizona.

There are a few other permissive double lefts in the Phoenix area, and most are fairly old. Excluding those in places like Chandler, where the permissive phase never seems to activate, these are quite new and are effectively in permissive mode 100% of the time. I'm sure Maricopa County would install fully-protected left turns once Sarival Road is fully widened, and the Parkway's easterly extension is complete. But they probably realized how quiet the area would be until such point, so they installed five-section towers until then. Well done, Maricopa County.

This is interesting to me, as it's a dual permissive left setup at a seemingly under capacity intersection clearly built with future turning volumes in mind. The same intersection constructed in Nevada would likely have the inner turn lane blocked off with chevrons until demand necessitated its use, at the same time the permitted left would likely be removed for protected lefts.

EDIT: I don't know the volumes on Sarival Rd. But after looking at the intersection further and the movements currently existing, they probably could have gotten away with not activating this signal at all until future phases of Northern Pkwy open.

[jakeroot]

Totally forgot to post this example that I found a few weeks ago:

Left turn from southbound Sarival Road to eastbound Northern Parkway, outside Waddell, Arizona.

There are a few other permissive double lefts in the Phoenix area, and most are fairly old. Excluding those in places like Chandler, where the permissive phase never seems to activate, these are quite new and are effectively in permissive mode 100% of the time. I'm sure Maricopa County would install fully-protected left turns once Sarival Road is fully widened, and the Parkway's easterly extension is complete. But they probably realized how quiet the area would be until such point, so they installed five-section towers until then. Well done, Maricopa County.

This is interesting to me, as it's a dual permissive left setup at a seemingly under capacity intersection clearly built with future turning volumes in mind. The same intersection constructed in Nevada would likely have the inner turn lane blocked off with chevrons until demand necessitated its use, at the same time the permitted left would likely be removed for protected lefts.

EDIT: I don't know the volumes on Sarival Rd. But after looking at the intersection further and the movements currently existing, they probably could have gotten away with not activating this signal at all until future phases of Northern Pkwy open.

I think Washington State, and probably most other states, would have done the same. Judging by ADT numbers from Maricopa County, no section of Sarival Road averages more than ~1200 vehicles/day. Even if all of those cars turned onto Northern Pkwy, I doubt two left turn lanes is necessary.

With that said, I don't know about crash numbers. If there is no history of crashes at the intersection, it's not like two turn lanes hurts anything. Catch is, Arizona (apparently) doesn't make their crash data available for free. So I can't verify that claim. I can only assume, from imagery available from Street View, that the area is relatively quiet and likely doesn't not see many (if any) regular collisions.

[Roadwarriors79]

FWIW, the traffic signals at the Northern Parkway interchanges with Sarival Road, Reems Road, and Litchfield Road are all operated by the city of Glendale.

[jakeroot]

FWIW, the traffic signals at the Northern Parkway interchanges with Sarival Road, Reems Road, and Litchfield Road are all operated by the city of Glendale.

Thanks. I know the Northern Parkway is a Maricopa County project, but as with any locality, the management of the signals at the ramp termini varies.

[mrsman]

FWIW, the traffic signals at the Northern Parkway interchanges with Sarival Road, Reems Road, and Litchfield Road are all operated by the city of Glendale.

Thanks. I know the Northern Parkway is a Maricopa County project, but as with any locality, the management of the signals at the ramp termini varies.

This is definitely a case where they put in all the infrastructure necessary for the future in the present.  While it may make some sense to do all of the work involved for the interchange, including widening Sarival, double left turn lanes, and the signal infrastructure, while they are working on the project - I don't see how having the traffic signal operating (including the usage of electricity) is justified until traffic levels increase, probably as the area gets more developed.  In other areas, the signals would be off and covered until traffic picks up, with the use of temproary stop signs as needed.

[Amtrakprod]

Cedar Ridge TX:
https://www.google.com/maps/@30.5090378,-97.7872553,3a,75y,182.83h,87.22t/data=!3m6!1e1!3m4!1sfjq8NdbIipcZ2HROPuFNiQ!2e0!7i16384!8i8192
Pedestrian phase dual permissive.

[jakeroot]

Cedar Ridge TX:
https://www.google.com/maps/@30.5090378,-97.7872553,3a,75y,182.83h,87.22t/data=!3m6!1e1!3m4!1sfjq8NdbIipcZ2HROPuFNiQ!2e0!7i16384!8i8192
Pedestrian phase dual permissive.

Good find. Usually in those circumstances, the crosswalk is against right-turning traffic. This is fairly unusual, but reminds me of this T-intersection in Vancouver, BC (double left yield to peds, no crosswalk along right edge).

[jakeroot]

According to the video below (jump to 0:35), W 1st @ Main in downtown Los Angeles used to be a double permissive left turn, with the outermost left turn being an optional left/straight lane. Main was a one-way going left, so there was no oncoming left turns:

https://www.youtube.com/watch?v=6a5xDAUNBUA&t=3s

The current intersection has a single left turn lane, with no indication since Street View imagery began that it was removed anytime recently.

I really don't know of any in California at this point (not surprising given how conservative they are with permissive turns in general), but it's interesting to think that LA was even more liberal with left turns than they are now (very, compared to the rest of California).

[mrsman]

According to the video below (jump to 0:35), W 1st @ Main in downtown Los Angeles used to be a double permissive left turn, with the outermost left turn being an optional left/straight lane. Main was a one-way going left, so there was no oncoming left turns:

https://www.youtube.com/watch?v=6a5xDAUNBUA&t=3s

The current intersection has a single left turn lane, with no indication since Street View imagery began that it was removed anytime recently.

I really don't know of any in California at this point (not surprising given how conservative they are with permissive turns in general), but it's interesting to think that LA was even more liberal with left turns than they are now (very, compared to the rest of California).

Love the video.  13 year old me probably went through about half of those points at some point during the late 80's/early 90's.

[mrsman]

Cedar Ridge TX:
https://www.google.com/maps/@30.5090378,-97.7872553,3a,75y,182.83h,87.22t/data=!3m6!1e1!3m4!1sfjq8NdbIipcZ2HROPuFNiQ!2e0!7i16384!8i8192
Pedestrian phase dual permissive.

Good find. Usually in those circumstances, the crosswalk is against right-turning traffic. This is fairly unusual, but reminds me of this T-intersection in Vancouver, BC (double left yield to peds, no crosswalk along right edge).

While this is your thread Jake, I would prefer that examples like this not be included.  There are probably many intersections out there with some form of double left that doesn't need to yield to vehicular traffic, but yields to pedestrians.  Basically, T-intersections or one-way streets.  But these are really different from situations where you would yield to vehicles in the way that you approach them. 

If there is no opposing traffic, in what sense are you making a permissive turn?  The turn is functionally equivalent to a right turn, as you have to watch for pedestrians, but during green ball phase you have no vehicles to watch out for.

In those situations, the vast majority will be turns with green ball (or perhaps FYA to highlight yielding to peds).  Very few of this situation would involve a red arrow, protected only turn (such as very high pedestrian volume).

[jakeroot]

While this is your thread Jake, I would prefer that examples like this not be included.  There are probably many intersections out there with some form of double left that doesn't need to yield to vehicular traffic, but yields to pedestrians.  Basically, T-intersections or one-way streets.  But these are really different from situations where you would yield to vehicles in the way that you approach them. 

If there is no opposing traffic, in what sense are you making a permissive turn?  The turn is functionally equivalent to a right turn, as you have to watch for pedestrians, but during green ball phase you have no vehicles to watch out for.

In those situations, the vast majority will be turns with green ball (or perhaps FYA to highlight yielding to peds).  Very few of this situation would involve a red arrow, protected only turn (such as very high pedestrian volume).

No, it's good. You make a legitimate point. I'm sure they're far more common than regular dual-permissive left turns. I don't personally know of any that work this way in WA (all my local examples are from British Columbia), which is why I was initially fine with their inclusion. But all things considered, traffic control-wise, it's certainly not as interesting as a dual permissive left across traffic.

Nevertheless, if someone wanted to share a location where a traffic light works in this fashion, I'm not sure where else they'd post about it. Another reason I was fine with it. If I ran into one in Washington, I might have considered posting it here with the caveat that it's not a true "double permissive left turn" in the sense that there is no "oncoming" vehicular traffic.

[Revive 755]

For those agencies that are hesitant about a dual permissive left, but need the capacity of dual lefts in the peak hour: I wonder if there's a way you could program a signal and adequately sign/stripe the intersection so that the second turn lane is used only in the peak hour during protected-only mode, but leave one lane for permitted lefts during non-peak hours...

Seems North Carolina is going to test this, per https://www.ncdot.gov/news/press-releases/Pages/2020/2020-02-05-dynamic-left-turn-intersection.aspx

[Amtrakprod]

For those agencies that are hesitant about a dual permissive left, but need the capacity of dual lefts in the peak hour: I wonder if there's a way you could program a signal and adequately sign/stripe the intersection so that the second turn lane is used only in the peak hour during protected-only mode, but leave one lane for permitted lefts during non-peak hours...

Seems North Carolina is going to test this, per https://www.ncdot.gov/news/press-releases/Pages/2020/2020-02-05-dynamic-left-turn-intersection.aspx

Was gonna post that.


iPhone

[jakeroot]

Seems North Carolina is going to test this, per https://www.ncdot.gov/news/press-releases/Pages/2020/2020-02-05-dynamic-left-turn-intersection.aspx

Certainly interested to see how well observed the closed lane will be, particularly among drivers who might pass through the intersection 95% of the time during peak hours (and would thus be used to dual-lane operation).

[Amtrakprod]

Check this one out in Austin:
https://www.google.com/maps/@30.2640864,-97.7473521,3a,15y,105.54h,94.25t/data=!3m6!1e1!3m4!1sRWXg6oGRRUJE-iDtfcOdMw!2e0!7i16384!8i8192

[Amtrakprod]

and this one ish:
https://www.google.com/maps/@30.263465,-97.7445535,3a,69.1y,272.48h,92.44t/data=!3m6!1e1!3m4!1s7NkP_h9llho9Wl_j6sQfSQ!2e0!7i16384!8i8192

[jakeroot]

Check this one out in Austin:
https://www.google.com/maps/@30.2640864,-97.7473521,3a,15y,105.54h,94.25t/data=!3m6!1e1!3m4!1sRWXg6oGRRUJE-iDtfcOdMw!2e0!7i16384!8i8192

That's a long one; I'm guessing lagging green arrows. Great find! Texas seems to have quite a few, but given the urban area and two-way traffic, I consider it thread-worthy.

and this one ish:
https://www.google.com/maps/@30.263465,-97.7445535,3a,69.1y,272.48h,92.44t/data=!3m6!1e1!3m4!1s7NkP_h9llho9Wl_j6sQfSQ!2e0!7i16384!8i8192

This is the same link as before.

[Amtrakprod]

I'm pretty sure it's a different link. Lemme try again:
https://www.google.com/maps/@30.2632756,-97.7443458,3a,15y,308.79h,91.64t/data=!3m6!1e1!3m4!1sd9fUTu96VCquggQIJrfisA!2e0!7i16384!8i8192

[jakeroot]

I'm pretty sure it's a different link. Lemme try again:
https://www.google.com/maps/@30.2632756,-97.7443458,3a,15y,308.79h,91.64t/data=!3m6!1e1!3m4!1sd9fUTu96VCquggQIJrfisA!2e0!7i16384!8i8192

Got it. Hard to tell what's going on. In this link, it looks like it might be split-phased when the double left turn is activated. Thinking this because there are cars waiting to turn at the double left (spin camera around), but no green arrow was afforded to them.

[Amtrakprod]

it also has dallas phasing!

[jakeroot]

it also has dallas phasing!

Are we sure? Because it could be split phasing. Dallas phasing can have that appearance, unless Google Street View shows (within the same set of images) a permissive mode, followed by a protected green arrow for only one of the movements. Seeing only one direction with a green arrow (at a typical 5-section display), when the other direction also has a ton of waiting cars, is either caused by one of the directions having a lagging protected green arrow (fully protected left turn), no protected turn at all, or (rarely) the intersection operating protective/permissive most of the time, and split-phased during other times.