Double left turns with permissive phasing

[jakeroot]

DC is going through a process of adjusting the signals on all double turns to avoid conflict with pedestrians.  I don't believe there were any double lefts permissive against opposing traffic [which is the main emphasis of this thread], but there were double lefts and double rights against pedestrians that are now going to become protected only turns to separate turning traffic from pedestrians.

In the name of Vision Zero.

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

There are/were definitely a bunch. Quite a few of those mentioned in the "completed" column were against traffic.

Probably the busiest was westbound Independence at 12th St SW, which I captured a video of last year (note two lanes of traffic waiting to turn left at the beginning):

https://youtu.be/x5RbNLwuoqc

The intersection was definitely awkward given the sheer number of movements occurring simultaneously, plus the overlapping turns and the yellow trap for eastbound Independence traffic. Oh my!

My mother works just a couple blocks from the intersection, and I've walked through it many times before (especially given the metro stop right on that corner). For as busy as it is, I don't recall any collisions or even close calls. Everything moves fairly slow, and there's so many pedestrians that it's basically impossible to not notice them.

Oddly, none of the mentioned intersections are this one at Louisiana NW and New Jersey NW, a near-classic double permissive left (with an option lane). Guess this one stays.



From a layman's perspective, something I think would really help DC would be better channelization of lanes. Independence @ 12th St SW could easily be improved with offsetting the left turn lanes, and certainly some improved markings would help, but I guess it's just too expensive

[mrsman]

3rd/Independence seems to be one of the first examples of what is going on here.

Plus, it seems like the old and new configurations can be found on GSV.

Original configuration has a left turn lane and an option left/straight lane.  Permissive lagging left (opposing lefts prohibited).  Because of this, it isn't too dangerous to allow the permissive phasing.  Opposing lefts prohibited, so the opposing lefts don't block the view.  And most of teh time, it's busy enough that no turns are happening during the permissive phase anyway, but where opposing traffic is light, you won't block the straight traffic since you don't have to wait for the green arrow.

Now, to accommodate pedestrian safety, the option lane became a left turn lane and it is controlled by protected only lefts.

-------

As one considers this whole topic, there seem to be certain things that are common in these situations.  Certain states like Arizona, Colorado, and Texas tend to be more permissive than others.  More common in situations where opposing lefts are prohibited.  More common where there are option lanes rather than full double lanes.  Any other general observations, Jake?

[fwydriver405]

Found this one in Nogales AZ near the southern terminus of Interstate 19. The one on Grand Ave is a definite yes, but not sure about the one on Crawford St where one of the approaches are right turn only:

Grand Ave to Crawford St/I-19 N (definite yes)

Crawford St (unsure about)

[jakeroot]

As one considers this whole topic, there seem to be certain things that are common in these situations.  Certain states like Arizona, Colorado, and Texas tend to be more permissive than others.  More common in situations where opposing lefts are prohibited.  More common where there are option lanes rather than full double lanes.  Any other general observations, Jake?

Not a whole lot, beyond where they're most common.

Many of the Texas variants have surprised me with their negative-offset construction, like this one in Fort Worth that was disabled due to a high number of crashes. Colorado also has a surprising number without any consideration of oncoming visibility, but they don't (usually) construct medians on the left (without any gap on the right, like Tucson) that make visibility worse than without any median. Unlike Texas, I've not heard of any being shut off in Colorado, so they must be better-trained at handling these (not surprising given the sheer number across Colorado ... probably the highest per-capita in the US).

Another observation might be that they are sometimes used without consideration at side-streets, where there is limited available green time to call for separate movements. Three examples of this have existed along Montlake Boulevard in Seattle: here (with a severe path overlap) and here; a third example now operates with flashing yellow right arrows for oncoming traffic, as does another to the south at equally-busy Rainier Ave.

In a similar vein, they are more common when opposite a driveway; Pierce County, WA's only example of a double-permissive left was this kind of setup (now split-phased); another example in Tucson like this. The one in Boston just up-thread is opposite a driveway leaving city hall as well.

Another minor observation would be Washington and Oregon's lack of interest in prohibiting double-left turns onto on-ramps during red periods. Neither DOT installs double-left turns with true permissive phasing (yield on green, or yield on FYA), but rarely (if ever) prohibit double left turns on red from two-way to one-way streets. This is not a true double-permissive left in the spirit of this thread, but it's an interesting observation. In practice, they don't work any different than Maryland's flashing red arrows (though stopping is absolutely required). Idaho and Michigan have similar laws, though the former does not allow turns against red arrows, and the latter already has several true permissive double left turns along state highways, unlike Washington and Oregon.

[jakeroot]

Found this one in Nogales AZ near the southern terminus of Interstate 19. The one on Grand Ave is a definite yes, but not sure about the one on Crawford St where one of the approaches are right turn only:

Grand Ave to Crawford St/I-19 N (definite yes)

Crawford St (unsure about)

Looks to me like the latter also operates with permissive phasing. I believe that the green arrows should be green orbs, as green arrows are not to be used when other traffic that may conflict with that movement, has anything other than a red indication. This rule is ignored fairly often these days, with the normalisation of right-turn signals (particularly those with flashing yellow arrows), but I think the rule still remains.

[kphoger]

The worst I've personally driven through is this example in Coahuila.  A single overhead signal for each direction of a four-lane divided federal highway with very heavy commercial traffic.

Yikes, that is bad. Looks to run split-phasing as well. Also not so good.

While split phasing is quite common in Mexico, I don't think this one does.  I could be wrong, but I don't see any left turn arrows to make me think it does either.

I was basing it on these views:

https://goo.gl/maps/ME7bkpc2ZEvL1yFPA

https://goo.gl/maps/BMJgXEpGcc6ZgCTq5

Yeah, I noticed that too.  I don't remember from personal experience, but I don't see how that would work without arrows.

Confirmed in person a week ago.

This stoplight runs split phasing with a single signal head in each direction and no arrows.  Even though left turns are therefore protected, you'd never know it by looking at the signal.

AADT here was 14,330 last year, with 23% buses and trucks.

[jakeroot]

Confirmed in person a week ago.

This stoplight runs split phasing with a single signal head in each direction and no arrows.  Even though left turns are therefore protected, you'd never know it by looking at the signal.

AADT here was 14,330 last year, with 23% buses and trucks.

Really appreciate the update! Seems like Mexico is seriously lacking in proper signalisation outside of certain areas (Northern Mexico seems to be in worse shape).

[jakeroot]

Found another in Chicago: https://goo.gl/maps/Zn42Wji2djFMVPdd9

This brings the Chicago area to three four known installations:

N Sheridan Road @ W Bryn Mawr Ave (option lane)
N Columbus Drive (NB) @ E Grand Ave (former option lane, now two dedicated turns) (NEW)
N Columbus Drive (SB) @ E Illinois Street (former option lane, now two dedicated turns) (NEW)
Thorndale Ave @ Park Blvd, Itasca (true double left) (removed, now an off-ramp from the 390 Toll Road)

Found more in Chicago. Both seem to be a fairly central area, so I'm definitely surprised someone hasn't mentioned either:

E Jackson Drive (WB) @ S Columbus Drive (option lane) (NEW)
E Monroe Street (EB) @ LSD (two dedicated turn lanes) (NEW) (no protected phase)

Chicago has quickly become #1 among largest US cities! Of the ten largest cities, those in Texas might have some onto frontage roads, but these are so damn common I don't feel like including them on this list. Really not until you get towards Seattle or Denver, do you get cities with at least a couple of known installations (Denver having quite a few, Seattle having less than in the past). Eventually, down at #34, is Tucson, which is still reigning champ AFAIK.

[mrsman]

Found another in Chicago: https://goo.gl/maps/Zn42Wji2djFMVPdd9

This brings the Chicago area to three four known installations:

N Sheridan Road @ W Bryn Mawr Ave (option lane)
N Columbus Drive (NB) @ E Grand Ave (former option lane, now two dedicated turns) (NEW)
N Columbus Drive (SB) @ E Illinois Street (former option lane, now two dedicated turns) (NEW)
Thorndale Ave @ Park Blvd, Itasca (true double left) (removed, now an off-ramp from the 390 Toll Road)

Found more in Chicago. Both seem to be a fairly central area, so I'm definitely surprised someone hasn't mentioned either:

E Jackson Drive (WB) @ S Columbus Drive (option lane) (NEW)
E Monroe Street (EB) @ LSD (two dedicated turn lanes) (NEW) (no protected phase)

Chicago has quickly become #1 among largest US cities! Of the ten largest cities, those in Texas might have some onto frontage roads, but these are so damn common I don't feel like including them on this list. Really not until you get towards Seattle or Denver, do you get cities with at least a couple of known installations (Denver having quite a few, Seattle having less than in the past). Eventually, down at #34, is Tucson, which is still reigning champ AFAIK.

Monroe/LSD is against a driveway from a Yacht Club.  while still a double permissive turn, given that it is a private driveway, it is unlikely to get too much traffic.

I.e. aside from a small amount of driveway traffic, this is essentially a T-intersection.

[jakeroot]

Monroe/LSD is against a driveway from a Yacht Club.  while still a double permissive turn, given that it is a private driveway, it is unlikely to get too much traffic.

I.e. aside from a small amount of driveway traffic, this is essentially a T-intersection.

Indeed, not a ton of oncoming traffic (certainly the reason why there is no protected phase). But there is a lot of pedestrian traffic, and there does appear to be at least a few major attractions along that driveway, so I would still include it in this thread. It seems like it would be busy enough during tourist season (whenever this is, in Chicago).

As far as double left turns across driveways, I'm not against including them. I would absolutely include them, but I think each has to be considered on its individual merits: does it seem to get a lot of traffic? Does the driveway serve several businesses? Etc, etc. If it's just a regular turn across a single driveway from a home? Boring. But a double left turn across a private drive that has several active businesses and a lot of foot traffic to boot? That's pretty damn interesting.

More to the point, would the left turn receive split phasing or regular protected phasing in most municipalities? If the answer is "yes", it's worthy of this thread IMO.

[mrsman]

Monroe/LSD is against a driveway from a Yacht Club.  while still a double permissive turn, given that it is a private driveway, it is unlikely to get too much traffic.

I.e. aside from a small amount of driveway traffic, this is essentially a T-intersection.

Indeed, not a ton of oncoming traffic (certainly the reason why there is no protected phase). But there is a lot of pedestrian traffic, and there does appear to be at least a few major attractions along that driveway, so I would still include it in this thread. It seems like it would be busy enough during tourist season (whenever this is, in Chicago).

As far as double left turns across driveways, I'm not against including them. I would absolutely include them, but I think each has to be considered on its individual merits: does it seem to get a lot of traffic? Does the driveway serve several businesses? Etc, etc. If it's just a regular turn across a single driveway from a home? Boring. But a double left turn across a private drive that has several active businesses and a lot of foot traffic to boot? That's pretty damn interesting.

More to the point, would the left turn receive split phasing or regular protected phasing in most municipalities? If the answer is "yes", it's worthy of this thread IMO.

Sure, it merits inclusion because it is still yielding to opposing traffic.  It just should be noted that since it is practically at the end of the road (only a few feet from Lake Michigan), the nature of traffic coming out of the driveway is not huge.  Although, yes, technically more than at a private driveway.

Chicago is sort of interesting in this degree.   Yes, it should be celebrated that there are quite a number of intersections with permissive double lefts.  But it has other issues that I strongly disagree with.  It seems to have many intersections with 5 aspect signals that are left on green arrow only, when that type of signal is almost universally used for PPLTs.  Yes there is signage to that effect, but it still defies the general expectation.

[jakeroot]

Monroe/LSD is against a driveway from a Yacht Club.  while still a double permissive turn, given that it is a private driveway, it is unlikely to get too much traffic.

I.e. aside from a small amount of driveway traffic, this is essentially a T-intersection.

Indeed, not a ton of oncoming traffic (certainly the reason why there is no protected phase). But there is a lot of pedestrian traffic, and there does appear to be at least a few major attractions along that driveway, so I would still include it in this thread. It seems like it would be busy enough during tourist season (whenever this is, in Chicago).

As far as double left turns across driveways, I'm not against including them. I would absolutely include them, but I think each has to be considered on its individual merits: does it seem to get a lot of traffic? Does the driveway serve several businesses? Etc, etc. If it's just a regular turn across a single driveway from a home? Boring. But a double left turn across a private drive that has several active businesses and a lot of foot traffic to boot? That's pretty damn interesting.

More to the point, would the left turn receive split phasing or regular protected phasing in most municipalities? If the answer is "yes", it's worthy of this thread IMO.

Sure, it merits inclusion because it is still yielding to opposing traffic.  It just should be noted that since it is practically at the end of the road (only a few feet from Lake Michigan), the nature of traffic coming out of the driveway is not huge.  Although, yes, technically more than at a private driveway.

Chicago is sort of interesting in this degree.   Yes, it should be celebrated that there are quite a number of intersections with permissive double lefts.  But it has other issues that I strongly disagree with.  It seems to have many intersections with 5 aspect signals that are left on green arrow only, when that type of signal is almost universally used for PPLTs.  Yes there is signage to that effect, but it still defies the general expectation.

Indeed. On many fronts, Illinois leads the midwest (hell, the country) in their signalization efforts, with many intersections resembling California-style placement but with many single-lane left turns using permissive phasing (unlike most of California), and apparently quite a few double lefts using it as well. But then yes, in Chicago, you have those ridiculous "on green arrow only" signs along several major arterials. I can only assume they were installed to satisfy the Chicago DOT's requirements for X-number of through signal heads, a difficult task for those arterials where protected phasing is desired but where overhead signals are not used. But that's a fairly poor excuse with advances in signal technology and placement strategies, and things should have been fixed a while ago.

I have wondered, given the Illinois tendency to push as far forward into the intersection as possible when turning (my method, but standard Illinois practice too), if some of the "on green arrow only" signs were removed, such as the one at Monroe/LSD, if drivers would instinctively start to turn with the green ball? Or even they'd get on autopilot and wait for the green arrow anyway. Based on what I know about "FIBs", I'm surprised they're obeyed at all.

[Amtrakprod]

Monroe/LSD is against a driveway from a Yacht Club.  while still a double permissive turn, given that it is a private driveway, it is unlikely to get too much traffic.

I.e. aside from a small amount of driveway traffic, this is essentially a T-intersection.

Indeed, not a ton of oncoming traffic (certainly the reason why there is no protected phase). But there is a lot of pedestrian traffic, and there does appear to be at least a few major attractions along that driveway, so I would still include it in this thread. It seems like it would be busy enough during tourist season (whenever this is, in Chicago).

As far as double left turns across driveways, I'm not against including them. I would absolutely include them, but I think each has to be considered on its individual merits: does it seem to get a lot of traffic? Does the driveway serve several businesses? Etc, etc. If it's just a regular turn across a single driveway from a home? Boring. But a double left turn across a private drive that has several active businesses and a lot of foot traffic to boot? That's pretty damn interesting.

More to the point, would the left turn receive split phasing or regular protected phasing in most municipalities? If the answer is "yes", it's worthy of this thread IMO.

Sure, it merits inclusion because it is still yielding to opposing traffic.  It just should be noted that since it is practically at the end of the road (only a few feet from Lake Michigan), the nature of traffic coming out of the driveway is not huge.  Although, yes, technically more than at a private driveway.

Chicago is sort of interesting in this degree.   Yes, it should be celebrated that there are quite a number of intersections with permissive double lefts.  But it has other issues that I strongly disagree with.  It seems to have many intersections with 5 aspect signals that are left on green arrow only, when that type of signal is almost universally used for PPLTs.  Yes there is signage to that effect, but it still defies the general expectation.

Indeed. On many fronts, Illinois leads the midwest (hell, the country) in their signalization efforts, with many intersections resembling California-style placement but with many single-lane left turns using permissive phasing (unlike most of California), and apparently quite a few double lefts using it as well. But then yes, in Chicago, you have those ridiculous "on green arrow only" signs along several major arterials. I can only assume they were installed to satisfy the Chicago DOT's requirements for X-number of through signal heads, a difficult task for those arterials where protected phasing is desired but where overhead signals are not used. But that's a fairly poor excuse with advances in signal technology and placement strategies, and things should have been fixed a while ago.

I have wondered, given the Illinois tendency to push as far forward into the intersection as possible when turning (my method, but standard Illinois practice too), if some of the "on green arrow only" signs were removed, such as the one at Monroe/LSD, if drivers would instinctively start to turn with the green ball? Or even they'd get on autopilot and wait for the green arrow anyway. Based on what I know about "FIBs", I'm surprised they're obeyed at all.

I would agree. If i had to rank traffic lights in the USA, Illinois is first place easily.


iPhone

[jakeroot]

I would agree. If i had to rank traffic lights in the USA, Illinois is first place easily.

I might still put California first, but only because of their consistency. Illinois has some terrible inconsistencies. Springfield has more consistent (and thorough) placement strategies than Bloomington, for example (who uses only basic Illinois requirements: two signals for every movement). Apparently near-side signals are not an absolutely requirement in Illinois. It just so happens that Chicago and surrounding municipalities (including ISTHA) have really good strategies.

[deathtopumpkins]

IMHO California has way too many protected lefts to ever rank first.

[mrsman]

IMHO California has way too many protected lefts to ever rank first.

Correct, only first in signal placement.  Near dead last in signal operation.

[fwydriver405]

IMHO California has way too many protected lefts to ever rank first.

Correct, only first in signal placement.  Near dead last in signal operation.

Found this one in Downtown San Francisco (option lane). The left lane can choose between I-80 E or Bryant St, and the middle to Bryant St or continue straight to 5th St. Many drivers I've seen during rush hour, use the middle lane to turn onto I-80 E...

I believe there's another one somewhere in SF but not sure where.

EDIT: A few more -
Van Ness and Broadway (albeit temporary? - 2 left turn lanes converted from left + option)
Sloat Blvd and 19th Ave (left + option)

[jakeroot]

^^
Holy s***! I didn't think California had any of these (left from earlier years or otherwise). Awesome finds, fwydriver!

Literally the only two I've ever found in California, beyond any that may have existed at one-way streets in downtown LA back before the 2000s, were these two:

* Cupertino, outside of the new Apple Park during construction
* San Jose, exit from the Aligent Technologies Campus

To actually see not just one or two, but three proper double left turns along major city streets with signals is really cool, and not something I thought existed in California (at least not anymore...I do recognize that these appear to be old installations). The latter two (at Broadway, and at 19th Ave) are particularly cool because they aren't on to one-way streets, although there is no oncoming left turn.

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.

[mrsman]

IMHO California has way too many protected lefts to ever rank first.

Correct, only first in signal placement.  Near dead last in signal operation.

Found this one in Downtown San Francisco (option lane). The left lane can choose between I-80 E or Bryant St, and the middle to Bryant St or continue straight to 5th St. Many drivers I've seen during rush hour, use the middle lane to turn onto I-80 E...

I believe there's another one somewhere in SF but not sure where.

EDIT: A few more -
Van Ness and Broadway (albeit temporary? - 2 left turn lanes converted from left + option)
Sloat Blvd and 19th Ave (left + option)

Probably given the traffic demand, both lanes SHOULD be allowed to turn left onto the freeway.

[mrsman]

While good to see more of these, it is understandable to see the sf configurations.  No opposing left.  Lagging left.  Option lane.  Clear sightlines.

On very busy streets with option lanes, this signalization is ideal.  You may be ALLOWED to turn left during permissive phase, but practically speaking, you will only be ABLE to during the protected phase, during most parts of the day.  The typical concerns that normally disallow permissive double left don't really apply here.  And it's nice that the DOT recognizes it and allows for the possibility of permissive left and avoids split phasing. 

Nexus 5X

[jakeroot]

Found this one in Downtown San Francisco (option lane). The left lane can choose between I-80 E or Bryant St, and the middle to Bryant St or continue straight to 5th St. Many drivers I've seen during rush hour, use the middle lane to turn onto I-80 E...

Probably given the traffic demand, both lanes SHOULD be allowed to turn left onto the freeway.

I agree. There are three lanes on that on-ramp. No reason they couldn't allow a sharp double left turn.

[jakeroot]

While good to see more of these, it is understandable to see the sf configurations.  No opposing left.  Lagging left.  Option lane.  Clear sightlines.

On very busy streets with option lanes, this signalization is ideal.  You may be ALLOWED to turn left during permissive phase, but practically speaking, you will only be ABLE to during the protected phase, during most parts of the day.  The typical concerns that normally disallow permissive double left don't really apply here.  And it's nice that the DOT recognizes it and allows for the possibility of permissive left and avoids split phasing. 

Again, I agree with your points. Nevertheless, it surprises me that SF installed these to begin with. I never associated California with permissive left turns along major arterials (outside of LA proper), much less any that allow left turns from two lanes. I think most Californian municipalities, and even San Francisco themselves along any reconstructed arterials, would design the road layout in a manner appropriate for protected-only left turns if the road were designed today. Which is more than unfortunate IMO, since these seem to work adequately when properly designed.

[fwydriver405]

While good to see more of these, it is understandable to see the sf configurations.  No opposing left.  Lagging left.  Option lane.  Clear sightlines.

On very busy streets with option lanes, this signalization is ideal.  You may be ALLOWED to turn left during permissive phase, but practically speaking, you will only be ABLE to during the protected phase, during most parts of the day.  The typical concerns that normally disallow permissive double left don't really apply here.  And it's nice that the DOT recognizes it and allows for the possibility of permissive left and avoids split phasing. 

Again, I agree with your points. Nevertheless, it surprises me that SF installed these to begin with. I never associated California with permissive left turns along major arterials (outside of LA proper), much less any that allow left turns from two lanes. I think most Californian municipalities, and even San Francisco themselves along any reconstructed arterials, would design the road layout in a manner appropriate for protected-only left turns if the road were designed today. Which is more than unfortunate IMO, since these seem to work adequately when properly designed.

I believe Van Ness Ave is being reconstructed in that area to remove left turns in that area and to add bus lanes in the middle of the road. The only left turns that are being retained are:

SB Van Ness onto EB Broadway (the example I posted)
NB Van Ness onto WB Lombard (triple left turn lane, protected only)

I wonder what will happen with the SB Van Ness onto EB Broadway double left when the entire project is complete... especially with the new bus lanes.

Also, at least one SF intersection was converted from PPLT double left + thru to protected only recently. Harrison to I-80 E's (current) middle lane was converted from thru-left to a dedicated only left turn lane in 2013. Of course, they had to change the phasing from PPLT lag left to protected only. Still lagging left though... (pay attention to the arrow in the distant signal)

[jakeroot]

Also, at least one SF intersection was converted from PPLT double left + thru to protected only recently. Harrison to I-80 E's (current) middle lane was converted from thru-left to a dedicated only left turn lane in 2013. Of course, they had to change the phasing from PPLT lag left to protected only. Still lagging left though... (pay attention to the arrow in the distant signal)

So there was even more? Very interesting. Did you live in the area? Curious because that KRON4 video was from soon after the signal was modified, and the story seems to about the massive tailbacks being caused by that left turn. I would be interested in knowing how that signal modification has affected traffic flow. Usually the main arguments against these are either too many crashes, or pedestrian conflicts. But there doesn't seem to be that much oncoming traffic (total non-scientific observation), and there is no pedestrian crossing. So why the change? hmm.

I believe Van Ness Ave is being reconstructed in that area to remove left turns in that area and to add bus lanes in the middle of the road. The only left turns that are being retained are:

SB Van Ness onto EB Broadway (the example I posted)
NB Van Ness onto WB Lombard (triple left turn lane, protected only)

I wonder what will happen with the SB Van Ness onto EB Broadway double left when the entire project is complete... especially with the new bus lanes.

Typically with center bus lanes, any permissive left turns are eliminated, as traffic would have to yield to buses from behind them, oncoming buses, oncoming traffic, and pedestrians. Even I think this might be too much! South Africa, a haven for permissive right turns (they drive on the left), does not allow them across bus lanes, except where the buses do not have constant green lights (such as when they have to make turns).

The catch will be if the BRT lanes merge with general traffic near those left turns. If that happens, the left turns can probably stay, as the primary reason for eliminating permissive turns across bus lanes is due to buses coming from behind you. Barring that, there's no reason the double left onto Broadway would need to lose its permissive phase. At exceptionally busy turns, South Africa will merge buses with traffic, but the buses get a "pre-signal" that allows them to merge into the through lanes prior to the beginning of the turn lane. I've not seen this used elsewhere, but seems like an option for Van Ness @ Broadway and Lombard.

[mrsman]

While good to see more of these, it is understandable to see the sf configurations.  No opposing left.  Lagging left.  Option lane.  Clear sightlines.

On very busy streets with option lanes, this signalization is ideal.  You may be ALLOWED to turn left during permissive phase, but practically speaking, you will only be ABLE to during the protected phase, during most parts of the day.  The typical concerns that normally disallow permissive double left don't really apply here.  And it's nice that the DOT recognizes it and allows for the possibility of permissive left and avoids split phasing. 

Again, I agree with your points. Nevertheless, it surprises me that SF installed these to begin with. I never associated California with permissive left turns along major arterials (outside of LA proper), much less any that allow left turns from two lanes. I think most Californian municipalities, and even San Francisco themselves along any reconstructed arterials, would design the road layout in a manner appropriate for protected-only left turns if the road were designed today. Which is more than unfortunate IMO, since these seem to work adequately when properly designed.

I believe Van Ness Ave is being reconstructed in that area to remove left turns in that area and to add bus lanes in the middle of the road. The only left turns that are being retained are:

SB Van Ness onto EB Broadway (the example I posted)
NB Van Ness onto WB Lombard (triple left turn lane, protected only)

I wonder what will happen with the SB Van Ness onto EB Broadway double left when the entire project is complete... especially with the new bus lanes.

Also, at least one SF intersection was converted from PPLT double left + thru to protected only recently. Harrison to I-80 E's (current) middle lane was converted from thru-left to a dedicated only left turn lane in 2013. Of course, they had to change the phasing from PPLT lag left to protected only. Still lagging left though... (pay attention to the arrow in the distant signal)

San Francisco is pretty well known for having many major 2-way corridors that completely disallow nearly all left turns altogether:  19th Ave, Sunset, Geary.  In pre-construction days there were several intersections where lefts were prohibited from Van Ness, but it's true that more were allowed than just Lombard and Broadway.  Lombard-Van Ness - Broadway  is a main connecting route from the Golden Gate Bridge to Downtown SF, which is why there are multiple left turn lanes and why the lefts are still allowed even with the construction (and will probably still be allowed after the bus lanes are put in place).

I think that the bus lane would probably end at Greenwhich (one block south of Lombard).  They need some way to allow for that massive left turn, and there would be no additional room for a bus lane.  At Broadway, there will probably be a protected-only left (to be made from the lane that is to the right of the bus lane), but it may be limited to one lane.