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.

[Road Hog]

I did just discover one in the wild. Southbound Preston Road at Gaylord in Frisco, TX. It's late at night though with light traffic. I doubt it's the same in daytime.

[fwydriver405]

Encountered another double permissive left (L-LT) in Massachusetts, this time coming out of the Peabody Place in Peabody (At Route 114 at Palmer Ave and Peabody Place). Seems like this one has been there for a while, looking at GSV, even after the signals have been upgraded and repaving of the Peabody Place. Circular green indication for both approaches.

Also in MA, don't know if this has been mentioned before, but the double permissive left coming out of Cambridgeside Pl turning left onto Edwin H Land Blvd has been changed over to using split-phasing on both the Cambridgeside and Sonesta Hotel approaches as of Summer 2025. The other one, North St at Congress St in Boston, still has concurrent greens as of May 2026 (drove past this yesterday).


I also keep forgetting to post this example, but there is this protected-permissive double left in St. John, NB I recall seeing a while back (came across this again cleaning out some playlists on YT) - (Video, Maps)

[jakeroot]

I did just discover one in the wild. Southbound Preston Road at Gaylord in Frisco, TX. It's late at night though with light traffic. I doubt it's the same in daytime.

I do see it was changed to flashing yellow arrow displays recently. It's nice to see these time-of-day dual flashing yellow arrows.

As an aside, that whole northern Dallas area (Richardson / McKinney / Frisco) was, at least for a while, full of these types of left turns. I remember reading a Virginia DOT document from 15+ years ago (edit: read here, page 66) that had requested feedback from cities around the country about permissive double lefts. One engineer from Las Vegas, but previously from Richardson, mentioned that when they began to widely install double left turns in the 1980s (I guess they were much rarer before that), they just kept using the phasing they had been with single lefts. This is a legacy example from Richardson; GSV is from 2008 but it's still there today. There are tons of examples nearby.

TXDOT doesn't seem to care either, since permissive dual lefts onto frontage roads are common throughout the state.

[jakeroot]

I also keep forgetting to post this example, but there is this protected-permissive double left in St. John, NB I recall seeing a while back (came across this again cleaning out some playlists on YT) - (Video, Maps)

I'm not sure who made that video (you or someone else) but I feel they are being a bit dramatic. Seems to be working just fine.

That said, it seems like it previously used lagging phasing for the double left (GSV from 2009), which I feel is the best phasing for dual permissive turns in general, as it captures those waiting cars and really solidifies that left turns do not have the right of way. All of Japan's dual permissive right turns operate this way.

Frankly, the best left turn is a skipped left turn. Protected phases are not part and parcel if there's no cars waiting to turn. Let traffic turn and flip on the green arrow when/if needed.

[fwydriver405]

I also keep forgetting to post this example, but there is this protected-permissive double left in St. John, NB I recall seeing a while back (came across this again cleaning out some playlists on YT) - (Video, Maps)

I'm not sure who made that video (you or someone else) but I feel they are being a bit dramatic. Seems to be working just fine.

Nope, I did not make or tape the St. John's video that I linked in my reply. In fact, I have never been to St. John's, New Brunswick before (only have been to Moncton). Just encountered that video at some point in the past and saved it somewhere for later.

That said, it seems like it previously used lagging phasing for the double left (GSV from 2009), which I feel is the best phasing for dual permissive turns in general, as it captures those waiting cars and really solidifies that left turns do not have the right of way. All of Japan's dual permissive right turns operate this way.

Frankly, the best left turn is a skipped left turn. Protected phases are not part and parcel if there's no cars waiting to turn. Let traffic turn and flip on the green arrow when/if needed.

The only thing I probably would say is maybe put some dotted guide lines in the intersection to help guide drivers to stay in their lane during the turn, otherwise, I agree with you on that part. I probably guess it was flipped to leading, due to yellow trap into the driveway from the opposite side with a lagging left, but the risk is probably very low due to low turning movements onto there.

[kphoger]

TXDOT doesn't seem to care either, since permissive dual lefts onto frontage roads are common throughout the state.

Tangentially related...

WB US-82 @ SB I-35 frontage road in Gainesville originally had a single protected-only left turn lane.  Then it got an option lane, even though the left turn was still protected only.  I thought that was a great way to guarantee that at least one person would get rear-ended.  I see that they have now de-optioned the option lane.

[johndoe]

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!

That looks very wrong to my brain!  (Red circle with FYA on same signal head)

Also seems like a rear-end risk to have shared lane and give one red while the other FYA