Two Left Turn Lanes Changed to One

[Ned Weasel]

How often does this happen?

Look at this intersection before Google gets around to updating the imagery: https://goo.gl/maps/2KgAb7kLXz29R2Zh6 , https://goo.gl/maps/iGDpVbXaCqKFGw817

Well, today, I noticed this for the first time, when I went out for a bit:

Facing west (sorry about the sun glare; I tried to make it less obnoxious with a few minutes of adjusting):


Westbound lanes approaching intersection:


As you may have guessed from the new signal photo, they replaced the protected left turns with protected/permissive left turns (FYAs, per new standards).  They did this in both directions, as well as removing a turn lane in both directions.  It's probably safe to assume the City of Overland Park felt the dual left turn lanes from 151st Street were no longer warranted.  And I've noticed the city tends to use protected/permissive signals when there's only single signalized left turn lane, but sticks with protected-only signals when there are two left turn lanes (the two instances of triple left turn lanes don't really count, because those are coming from diamond interchange off-ramps).

Has anyone else seen this done anywhere else before?  I get that Overland Park probably wants to reduce signal phases on 151st Street.  Of course, I can't help but wonder whether they could've gone further with the concept and used downstream U-turns.

[Revive 755]

Dilleys Road at Nations Drive/Pinewood Drive in Gurnee, IL.  Used to have two left two lanes NB, now down to one

[roadfro]

Only one Nevada example comes to mind. Neil Road at S. Virginia St in Reno.

WB: There were 2 left turn lanes in October 2016 but reduced to one by June 2017.
EB: The lane configuration was 1 left, 1 left/thru, 1 thru & 1 right back in August 2011, but the shared left/thru lane was converted to left only by June 2017.

My hunch is that this they wanted to eliminate the E/W split phasing that had been in place, and ensure that left turns could proceed simultaneously if that signal timing would be advantageous. I'm guessing the intersection geometry might not have been able to accommodate that with double lefts in both directions, so the WB outer left turn lane was removed–I would guess that the WB left turn was a low volume movement anyway and a dual left wasn't needed to begin with.

Dilleys Road at Nations Drive/Pinewood Drive in Gurnee, IL.  Used to have two left two lanes NB, now down to one

Interesting that they could have implemented a positive offset for the left turn lane that would have increased visibility of oncoming traffic, but decided not to...

[CardInLex]

I-75 at KY 1973 (Iron Works Pike) in Lexington, KY has multiple dual lefts that were turned into one. And a dual right that was turned into one. This interchange was purposely overbuilt for the 2010 World Equestrian Games at the Kentucky Horse Park. After the event, the signals were removed and the dual turn lanes were striped out.


https://goo.gl/maps/h2mFD3EFMmgS6faq8

[Roadsguy]

This single left turn on US 30 in the Lancaster, PA area was once a double left turn. When PennDOT repaved US 30 here two years ago, they reduced it to a single left turn (even removing one of the two left turn signals) due to low volumes, though I'm not sure what harm would be done by just leaving it a double left turn. The road it turns onto is still two lanes, and while the westbound US 30 through lanes were shifted slightly, they didn't get any extra through capacity out of it.

[UCFKnights]

This single left turn on US 30 in the Lancaster, PA area was once a double left turn. When PennDOT repaved US 30 here two years ago, they reduced it to a single left turn (even removing one of the two left turn signals) due to low volumes, though I'm not sure what harm would be done by just leaving it a double left turn. The road it turns onto is still two lanes, and while the westbound US 30 through lanes were shifted slightly, they didn't get any extra through capacity out of it.

Orlandos done this a bit as well. One that always annoyed me while I was at UCF was at one of its entrances:
https://www.google.com/maps/@28.6021099,-81.2076249,3a,75y,333.48h,84.62t/data=!3m7!1e1!3m5!1spu-e-9GqLYH4bxfJRusWWg!2e0!5s20110301T000000!7i13312!8i6656

Siemens restriped their entrance from 2 lanes to 1 for some unknown reason, which left 2 left turn lanes turning into a 1 lane road. Several years later, they eventually striped over one of the left turn lanes. They still have 2 lanes marked to go straight into the single lane. It would have been much more logical to make them restripe that road back to 2 lanes.... but Orlando is awful at roads

[plain]

I can think of a few in Virginia:

VA 155 used to have double lefts at the entrance to Colonial Downs (fun fact - there was never a signal here*) but it's now just a single turn lane.

https://maps.app.goo.gl/3m7cssrsYtDguQhf8

US 15/29 in Opal used to have them at US 17 SB until a loop ramp and overpass was built further down

https://maps.app.goo.gl/RU3S9CxxARom9wHe8

VA 312 used to have double right turn lanes onto US 60 in Newport News but now it's a very long single turn lane. The double right went away in the late 1990's and the single lane now defaults onto a slip, since about 2006

https://maps.app.goo.gl/4ezP7qSi3fVW34Yf9


*One place with double lefts that should only be a single turn lane is on VA 134 Magruder Blvd at North Campus Pkwy in Hampton. Just like the VA 155 example, there was never a signal here.

[jakeroot]

First that comes to mind is the exit from a shopping center in Federal Way, WA. It was previously split-phased opposite a business driveway; three approach lanes, with the center lane able to turn left or right, or proceed straight. When the road was extended to become an arterial (S 352 St), the split-phasing was eliminated and the lanes became left/straight/right only, with no optional lanes.

Federal Way, WA; S 352 St @ WA-161 (before and after).

There is another I can think of in British Columbia. In Vancouver, the intersection of Burrard and Cornwall was previously a large intersection with many slip lanes. It was totally rebuilt about five years ago to be a more 'complete' intersection; the northbound left turn onto Cornwall was changed to a single lane left turn with these improvements. The other double turns (southbound to westbound, eastbound to northbound) remain.

Vancouver, BC; Burrard @ Cornwall (before and after).

[Ned Weasel]

First that comes to mind is the exit from a shopping center in Federal Way, WA. It was previously split-phased opposite a business driveway; three approach lanes, with the center lane able to turn left or right, or proceed straight. When the road was extended to become an arterial (S 352 St), the split-phasing was eliminated and the lanes became left/straight/right only, with no optional lanes.

Federal Way, WA; S 352 St @ WA-161 (before and after).

That reminds me of this example at I-49 in Grandview, MO.  It used to have a left-turn/straight-through option lane with double left turns allowed in the permissive phase, but they later changed it to a single left turn lane, and now there isn't even a permissive phase.  I was going to post this in the "Double left turns with permissive phasing" thread until I found out they changed it (I haven't driven on that cross-street in years).  I used to frequently turn left from the option lane, and one time somebody who didn't seem to understand the traffic control at the time honked at me for having the audacity to yield to oncoming traffic before proceeding through the intersection on the circular-green/permissive-left phase.

Previous: https://goo.gl/maps/RLoCb6YCmYgFWfYX9 , Current: https://goo.gl/maps/nqyF8jU3t1KamKP58

[GaryV]

Here's one that will be changed, once construction is done.

I-75 interchange at 14 Mile Road (Troy/Madison Heights border) is changing to a DDI.  Formerly there were 2 left turn lanes from wb 14 Mile to sb I-75.

With the DDI, is that a change from 2 lanes to 1, or to zero?

[mrsman]

First that comes to mind is the exit from a shopping center in Federal Way, WA. It was previously split-phased opposite a business driveway; three approach lanes, with the center lane able to turn left or right, or proceed straight. When the road was extended to become an arterial (S 352 St), the split-phasing was eliminated and the lanes became left/straight/right only, with no optional lanes.

Federal Way, WA; S 352 St @ WA-161 (before and after).

That reminds me of this example at I-49 in Grandview, MO.  It used to have a left-turn/straight-through option lane with double left turns allowed in the permissive phase, but they later changed it to a single left turn lane, and now there isn't even a permissive phase.  I was going to post this in the "Double left turns with permissive phasing" thread until I found out they changed it (I haven't driven on that cross-street in years).  I used to frequently turn left from the option lane, and one time somebody who didn't seem to understand the traffic control at the time honked at me for having the audacity to yield to oncoming traffic before proceeding through the intersection on the circular-green/permissive-left phase.

Previous: https://goo.gl/maps/RLoCb6YCmYgFWfYX9 , Current: https://goo.gl/maps/nqyF8jU3t1KamKP58

It is really odd that they downgraded the number of left turn lanes and also made the signal left on arrow only.  Usually, in cases like this, downgrading from two to one left turn lane allows for the opportunity of a PPLT, since many states restrict double left turns to protected only.

Also of note is that the left turn pockets don't seem to be long enough to contain the number of cars wanting to turn left (based on GSV pictures).  This is a frequent problem with many diamond interchanges as far as surface street is concerned.  And if that's the case, an even bigger reason not to do protected only lefts, because with PPLT, you effectively get a longer pocket because cars can pull into the intersection on green while waiting for a gap to turn.

https://www.google.com/maps/@38.8888933,-94.5250942,3a,75y,111.75h,90.55t/data=!3m6!1e1!3m4!1sr3ObuVwxYDy68aGmbhs93g!2e0!7i16384!8i8192

[mrsman]

DC has a big project to modify dual lanes into one all over the city, as part of pedestrian safety.  In some cases, they are implementing a separate pedestrian phase while keeping two turning lanes.  in other cases, they are downgrading double turns to single turns.

https://ddot.dc.gov/page/intersections-dual-turn-lanes

One that fits the thread the best is 17th at NY Ave, near the White House.

Before:  https://www.google.com/maps/@38.8958903,-77.0393966,3a,75y,354.07h,82.34t/data=!3m6!1e1!3m4!1sOFYUFOvxmZEP0vn1-JY3aA!2e0!7i13312!8i6656

After:
https://www.google.com/maps/@38.8958921,-77.0394301,3a,75y,354.07h,82.34t/data=!3m7!1e1!3m5!1sjy101HyXPQu5nvciQett1A!2e0!5s20181001T000000!7i16384!8i8192

[jakeroot]

First that comes to mind is the exit from a shopping center in Federal Way, WA. It was previously split-phased opposite a business driveway; three approach lanes, with the center lane able to turn left or right, or proceed straight. When the road was extended to become an arterial (S 352 St), the split-phasing was eliminated and the lanes became left/straight/right only, with no optional lanes.

Federal Way, WA; S 352 St @ WA-161 (before and after).

That reminds me of this example at I-49 in Grandview, MO.  It used to have a left-turn/straight-through option lane with double left turns allowed in the permissive phase, but they later changed it to a single left turn lane, and now there isn't even a permissive phase.  I was going to post this in the "Double left turns with permissive phasing" thread until I found out they changed it (I haven't driven on that cross-street in years).  I used to frequently turn left from the option lane, and one time somebody who didn't seem to understand the traffic control at the time honked at me for having the audacity to yield to oncoming traffic before proceeding through the intersection on the circular-green/permissive-left phase.

Previous: https://goo.gl/maps/RLoCb6YCmYgFWfYX9 , Current: https://goo.gl/maps/nqyF8jU3t1KamKP58

I've jokingly referred to on-ramps in that style (the original style, before it was modified) as "Texas lefts", as they have this total love-affair with double left turns involving option lanes that also use permissive phasing (on to their many frontage/service roads). If Colorado and parts of Arizona were eliminated from "the rankings", I think Texas has the most number of permissive double lefts, since this style of setup is extremely common in suburban and urban areas of Texas. I don't know how commonly they are built nowadays (they seem to have been common for many decades), as I've seen newer styles with double left turns that have dedicated lanes and dedicated protected-only phasing, but they're common enough that I'm not worried about them disappearing.

As mrsman mentions above, the modifications to that Grandview interchange are completely nonsensical. Double permissive left turn (even one with an option lane) must have at least three times the capacity of a single-lane protected-only left turn. Judging by GSV, local traffic is feeling the effects of this change. The change to having left turn pockets, which was required to introduce a dedicated left turn lane for the other on-ramp, also seems to have had negative effects (again, as mentioned by mrsman). Yet another odd thing: the other left turn has an FYA??? Why not for this other left turn?

I love Missouri. I lived in St Louis for a couple years on and off. But the state does some really weird things. St Louis-proper had great signalization. Makes me feel bad for people in other areas of the state, since MODOT can really do some odd stuff. Cool stuff, yes, but for every cool thing, something really odd like the changes to that Grandview intersection.

[jakeroot]

DC has a big project to modify dual lanes into one all over the city, as part of pedestrian safety.  In some cases, they are implementing a separate pedestrian phase while keeping two turning lanes.  in other cases, they are downgrading double turns to single turns.

https://ddot.dc.gov/page/intersections-dual-turn-lanes

One that fits the thread the best is 17th at NY Ave, near the White House.

Before:  https://www.google.com/maps/@38.8958903,-77.0393966,3a,75y,354.07h,82.34t/data=!3m6!1e1!3m4!1sOFYUFOvxmZEP0vn1-JY3aA!2e0!7i13312!8i6656

After:
https://www.google.com/maps/@38.8958921,-77.0394301,3a,75y,354.07h,82.34t/data=!3m7!1e1!3m5!1sjy101HyXPQu5nvciQett1A!2e0!5s20181001T000000!7i16384!8i8192

I would say that the entire District qualifies for this thread. I've only been living in DC on and off for a couple years, and I've already spotted numerous changes to double left turns around the city. The one at 17th and NY Ave was one that I spotted early on, since I often parked along E St when I didn't take the metro (going for a walk or something). Like many in the city, the setup was very odd and fairly nonsensical: same number of lanes leaving the intersection as arriving (three in the case of 17th/NY Ave), yet the movements possible at the intersection itself does not allow that number of lanes to proceed straight-on. Arrows really are king in DC, since the markings are otherwise rather confusing. Exact same setup remains today at 12th/Independence, as seen in the image below. As a side-note: they could seriously improve path overlap issues without removing the double left turn (a serious issue if you sit and observe the intersection for any length of time during normal rush hour) by removing the inside westbound lane leaving the intersection, and replacing it with an eastbound left turn lane. But what do I know?

For anyone else, this is my main issue with DC's double lefts:

[Ned Weasel]

As mrsman mentions above, the modifications to that Grandview interchange are completely nonsensical. Double permissive left turn (even one with an option lane) must have at least three times the capacity of a single-lane protected-only left turn. Judging by GSV, local traffic is feeling the effects of this change. The change to having left turn pockets, which was required to introduce a dedicated left turn lane for the other on-ramp, also seems to have had negative effects (again, as mentioned by mrsman). Yet another odd thing: the other left turn has an FYA??? Why not for this other left turn?

It's weirder the more we all look at it.  I have absolutely no idea why they went with the protected-only left turn signal instead of an FYA, which, as you observed, they used for the westbound-to-southbound left turn, unless there was an issue of eastbound visibility due to the slight hill.

I have to wonder about the traffic volumes for the turning movements.  If they're roughly equal for both left turns (eastbound-to-northbound, and westbound-to-southbound), then the re-striping makes sense.  And it's possible that the original configuration was put in place under the assumption that there would be more westbound-to-northbound left turns, because that's the direction in which one would go to get to the central city and the city center thereof.  However, I would suspect the most likely reason for removing the left turn from the option lane was people thinking it was a straight-through-only lane, and possibly rear-ending people out of inattentiveness.  But again, I don't know.

I love Missouri. I lived in St Louis for a couple years on and off. But the state does some really weird things. St Louis-proper had great signalization. Makes me feel bad for people in other areas of the state, since MODOT can really do some odd stuff. Cool stuff, yes, but for every cool thing, something really odd like the changes to that Grandview intersection.

I've long felt that MoDOT generally does a better job with roads closer to St. Louis.  Even though Kansas City is a larger city, the St. Louis metropolitan area is larger than the KC metro area, so perhaps it's a case of prioritization based on sheer population numbers.

On the Kansas side, it's been said, at least anecdotally, that people in Wichita are jealous of Johnson County because KDOT does a better job with the roads in Johnson County than in the Wichita area.  But again, Johnson County has a larger population than Sedgwick County, and, and when you combine the populations of the counties that comprise Kansas's side of the KC metro area, the population is much greater than that of the Wichita metropolitan area.  What other factors may be at play, I honestly don't know.

As a side-note: they could seriously improve path overlap issues without removing the double left turn (a serious issue if you sit and observe the intersection for any length of time during normal rush hour) by removing the inside westbound lane leaving the intersection, and replacing it with an eastbound left turn lane. But what do I know?

That's a simple re-striping that would solve at least two problems.  One, you'd have an eastbound left turn lane, and two, there would be no excuse for westbound traffic to change lanes in the intersection.

[STLmapboy]

I love Missouri. I lived in St Louis for a couple years on and off. But the state does some really weird things. St Louis-proper had great signalization. Makes me feel bad for people in other areas of the state, since MODOT can really do some odd stuff. Cool stuff, yes, but for every cool thing, something really odd like the changes to that Grandview intersection.

Their signalization is good, yes, but not always the most consistent. Some oldies in there (T-shaped mast arms, the Carthage light Hoger posted, tons of wires that definitely aren't "temporary").

[mrsman]

DC has a big project to modify dual lanes into one all over the city, as part of pedestrian safety.  In some cases, they are implementing a separate pedestrian phase while keeping two turning lanes.  in other cases, they are downgrading double turns to single turns.

https://ddot.dc.gov/page/intersections-dual-turn-lanes

One that fits the thread the best is 17th at NY Ave, near the White House.

Before:  https://www.google.com/maps/@38.8958903,-77.0393966,3a,75y,354.07h,82.34t/data=!3m6!1e1!3m4!1sOFYUFOvxmZEP0vn1-JY3aA!2e0!7i13312!8i6656

After:
https://www.google.com/maps/@38.8958921,-77.0394301,3a,75y,354.07h,82.34t/data=!3m7!1e1!3m5!1sjy101HyXPQu5nvciQett1A!2e0!5s20181001T000000!7i16384!8i8192

I would say that the entire District qualifies for this thread. I've only been living in DC on and off for a couple years, and I've already spotted numerous changes to double left turns around the city. The one at 17th and NY Ave was one that I spotted early on, since I often parked along E St when I didn't take the metro (going for a walk or something). Like many in the city, the setup was very odd and fairly nonsensical: same number of lanes leaving the intersection as arriving (three in the case of 17th/NY Ave), yet the movements possible at the intersection itself does not allow that number of lanes to proceed straight-on. Arrows really are king in DC, since the markings are otherwise rather confusing. Exact same setup remains today at 12th/Independence, as seen in the image below. As a side-note: they could seriously improve path overlap issues without removing the double left turn (a serious issue if you sit and observe the intersection for any length of time during normal rush hour) by removing the inside westbound lane leaving the intersection, and replacing it with an eastbound left turn lane. But what do I know?

For anyone else, this is my main issue with DC's double lefts:

As you brought it up, I do have a problem with the layout of both Constitution Ave and Independence Ave in Downtown DC.  Through the wide sections, they are 4 lanes in each direction, but no dedicated left turn lanes.  I always thought it would be better to have a 3-L-4 setup than a 4-4 because any minor left turn along the stretch could block an entire lane of traffic.  And, as you mention, it's even worse with a double left, as you effectively leave only two through lanes (one during non-rush hour, when parking is permitted).

Let's take a holistic approach to Independence:

Starting at Lincoln Memorial, we have a very fast good street with three lanes in each direction.  EB, a little while later, the right lane is forced off to Maine Ave and the middle lane is an option lane, leaving two lanes for Independence, but then immediately thereafter a new lane is available on the right to maintain 3 EB lanes.  This is a mistake, because at the next intersection, 15th you have 3 lanes in each direction, but no left turn lanes, so split-phasing is implemented which of course causes significant delay.  IMO, it would be better to maintain the two lanes EB from Maine Ave through the 15th st intersection until almost the 14th street intersection and allowing what is now the left EB lane to be used instead as a left turn lane, obviating the need for split-phasing.

At 14th, the street is 3-3 currently and it is fine since lefts are prohibited at all times (except for buses and taxis).  Crossing 14th, the street becomes 4-4, allowing for parking during non-rush hour.  The next intersection is at 12th, the one pictured above, and as jakeroot mentioned would be better organized as a 3-2L-3 rather than a 4-4.  So if full time parking were allowed between 12th and 14th, it would be better to have a P3-3P setup than 4-4, so that a lane shift can occur at intersections to accommodate left turns and still maintain three uninterrupted lanes in each direction.

East of there, there are no other double turns, and the street would probably be best designed as a P3-3P setup, that changes to prohibit parking near (major) intersections to accommodate a left turn lane.  While not common in the East Coast, Los Angeles does this routinely on many P2-2P streets in older parts of town with much success.  As an example, see Pico Blvd that is P2-2P for a large stretch in Mid-City but accommodates left turn pockets at Vermont, Normandie, and Western.

Pico  at Vermont:  https://www.google.com/maps/@34.0473282,-118.2914079,3a,75y,260.44h,83.54t/data=!3m6!1e1!3m4!1stmRUwFj4mHGdaxBjVgGH2g!2e0!7i16384!8i8192

(It may be easier to get a big picture view of this through satellite view of the full one mile between Vermont and Western.)

It should be noted that Independence Ave is only 8 lanes wide for a relatively short stretch.  Near the Capitol it narrows to only 4 lanes wide (2-2, but 3-1 reversible during rush hours).  4-4 just doens't seem to make any sense when more traffic can be accommodated with a 3-L-3P configuration, at least at intersections.