Double left turns with permissive phasing

[kphoger]

Oh, very nice. Definitely what I'd call a "legacy" example, looks from historic imagery that it was installed when Grove Street was created in the late 70s. At least the double left turn, not sure when it might have been made permissive.

What makes you assume it was ever not permissive?

[Tendies]

I forgot about this one less than three miles from my house, till I drove through it for the trillionth time yesterday.

Oh, very nice. Definitely what I'd call a "legacy" example, looks from historic imagery that it was installed when Grove Street was created in the late 70s. At least the double left turn, not sure when it might have been made permissive.

I came across this interesting one (Glenn Curtis Blvd EB at an office park) the other day with a shared left/through lane. The protected-permissive phasing can be seen in action in the GSV link. It makes an otherwise drab intersection seem exciting.

Also, it appears as though the double left from the office park is also permissive since there aren't any exclusive pedestrian signals for that crosswalk.

Great example of how option lanes can work. Making this an exclusive double left probably wouldn't be necessary most of the day, but could be useful during peak periods. Likewise, it likely wouldn't be wise to narrow the main road down to two through lanes just to accommodate that brief desire during peak periods. An option lane can let drivers determine what is best in the moment.

Pretty brave to trust the average driver to make that judgement. Maybe this could work in a small town not near major highways, but you know you'll have the one dude sitting in the option lane waiting to turn left during rush hour holding up traffic behind him. Especially during the 2024 October street view during the construction, where the option lane is the only lane that makes it past the next driveway.

[jakeroot]

Oh, very nice. Definitely what I'd call a "legacy" example, looks from historic imagery that it was installed when Grove Street was created in the late 70s. At least the double left turn, not sure when it might have been made permissive.

What makes you assume it was ever not permissive?

I don't want to assume anything. I'm sure it was always permissive, though.

Pretty brave to trust the average driver to make that judgement. Maybe this could work in a small town not near major highways, but you know you'll have the one dude sitting in the option lane waiting to turn left during rush hour holding up traffic behind him. Especially during the 2024 October street view during the construction, where the option lane is the only lane that makes it past the next driveway.

There are [normally] two more lanes to the right, anyone dumb enough to sit behind a driver turning left deserves whatever delay they have coming.

[CoreySamson]

There's a new double permissive right using FYAs at the new interchange between US 75 and 141st Street in Glenpool, OK that just got activated this past week. I will try to get a video of it in action soon.

The signal setup has three signals for a straight-thru lane, an option lane, and a right turn lane; the straight thru lane has a normal traffic signal, the option lane has a doghouse signal with a green up arrow on the bottom of the left and a FYA right arrow on the bottom on the right, and the right turn only lane has a FYA on the bottom. Really weird setup IMO.

Here's a video of this light in action as promised:

[jakeroot]

There's a new double permissive right using FYAs at the new interchange between US 75 and 141st Street in Glenpool, OK that just got activated this past week. I will try to get a video of it in action soon.

The signal setup has three signals for a straight-thru lane, an option lane, and a right turn lane; the straight thru lane has a normal traffic signal, the option lane has a doghouse signal with a green up arrow on the bottom of the left and a FYA right arrow on the bottom on the right, and the right turn only lane has a FYA on the bottom. Really weird setup IMO.

Here's a video of this light in action as promised:

Thanks for sharing.

I like how they keep the flashing yellow arrow active even when there is an oncoming left green arrow. Basically, makes it into a permanent slip lane. Pretty clever!

[Revive 755]

South Mall Drive at Harrison Street in Rockford, IL, appears to have been converted to effectively have a dual left (left only plus left-thru) on a flashing yellow arrow.  Streetview.

[jakeroot]

South Mall Drive at Harrison Street in Rockford, IL, appears to have been converted to effectively have a dual left (left only plus left-thru) on a flashing yellow arrow.  Streetview.

This looks to me like a case where they meant to convert it to dedicated left and straight lanes, but gave up after installing the signals. I assume this because the signals are not actually compliant for shared left/straight approaches. There's no dashed guide line for the left turn (which are not required but are used in Illinois for the most part), but that could be because the street view imagery was taken before final striping occured.

Can you confirm if you saw this in-person, or just in Google Street View?

[Revive 755]

^ So far I've only seen it on Streetview.  Also based on Streetview, it doesn't look like the guide line was being maintained during the latter years of the previous split phasing setup.

[jakeroot]

I was under the impression that, while they install them all the time, Minnesota almost never operates their dual left turns with flashing yellow arrow/permissive mode, except perhaps overnight.

With that in mind, I did see this intersection (County H at Mounds View Blvd, in Mounds View) that was operating permissively during daytime hours:

https://maps.app.goo.gl/wNbKFqrZHujnZ9W88

[tradephoric]

I was under the impression that, while they install them all the time, Minnesota almost never operates their dual left turns with flashing yellow arrow/permissive mode, except perhaps overnight.

With that in mind, I did see this intersection (County H at Mounds View Blvd, in Mounds View) that was operating permissively during daytime hours:

https://maps.app.goo.gl/wNbKFqrZHujnZ9W88

This isn't specifically related to the left turns, but i noticed there are pushbuttons in the median.  If there weren't PBs in the median it would require the side-street to run around 50 seconds to give pedestrians enough time to cross the road.  Assuming LT phases run around 30 seconds and the main-street needs 50 seconds to match the side-street, you are looking at a 160 second minimum cycle length.  Technically with pushbuttons you could run shorter cycles, but every time a pedestrian crosses the road it would push the signal out of step... not to mention pedestrians get stuck in the middle of the median with vehicles flying by them in each direction.  With these large intersections, it's just not an ideal situation.

1. You have dual left turns, you have longer pedestrian crossings. 
2. You have longer pedestrian crossings, you have longer cycle lengths. 
3. You have longer cycle lengths, you have longer left turn queues.
4. You have longer left turn queues, double-left turn lanes may not be enough.
5. You build an intersection with triple-lefts, go back to point 1.

[fwydriver405]

Sloat Blvd and 19th Ave (left + option)

EDIT: The one at Sloat/19th is also cool just because of how big the intersection is. Anywhere else in California, I suspect this would either be split-phased (as wasteful as that would be given the lack of an oncoming left), or the double left turns restriped without an option lane, and a protected-only signal put in place.

UPDATE: I did pass by this intersection this February 2026 and indeed, they did restripe the approach with two left-turn lanes, set to fully-protected - GSV suggests this was done between 2023 and 2024. In fact all of the examples from my original post(s) in SF are now fully protected with no permissive phasing at all anymore.