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[Roadwarriors79]

I don't know if this will be a trend in the city of Tucson, but they recently switched over one of their busier intersections (Speedway Blvd and Campbell Ave) to have protected left signals in all four directions. Interesting considering the vast majority of the left turn signals within city limits are permissive, even those with dual left turn lanes.

[i-215]

Wait...  a permissive dual left turn?  How on earth does that work?   

It seems to me that when traffic volumes reach a point that a second left lane is needed, it must automatically warrant a protected signal.  Not to mention the safety aspect of having two left lanes fighting to accept gaps in the oncoming traffic.

[roadfro]

Wait...  a permissive dual left turn?  How on earth does that work?   

It seems to me that when traffic volumes reach a point that a second left lane is needed, it must automatically warrant a protected signal.  Not to mention the safety aspect of having two left lanes fighting to accept gaps in the oncoming traffic.

Yeah, the dual permissive left turns thing has been discussed in another thread. It seems incredibly odd to me as well, as most practitioners would automatically move to protected left work dual turn lanes. But it seems to work fine for them, given the typical wide arterial medians and in-intersection yield lines in used where this control has been implemented.

[kdk]

I'm surprised they didn't use them in the past myself either.

I live in Phoenix and like Tucson we have lots of six lane arterial with dual left turn lanes.  All of them here have protected left turn signals, so when I'm in Tucson it feels a bit dangerous pulling out into the intersection to make a left. 

But it seems to work fine actually there.  This also includes the lagging left turn arrows that turn green immediately as the intersection light turns red, versus in Scottsdale where there is a couple of seconds in between.  Seems scary but never had an issue.

[JKRhodes]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

[ztonyg]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

[jakeroot]

I don't think this is related to the double left turn operation, especially since the approaches to Campbell Ave are single lane left turns. There are several single-lane protected lefts along Speedway that operate with TOD phasing, as can be seen in this Street View image: https://goo.gl/MGNdzr. The signs in the video are clearly unique in that "GREEN ARROW ONLY" signs are being used to restrict the movements to protected only, but it very well could be related to traffic levels. Or, in this case, a councillor who's getting involved where they shouldn't be. I would not be surprised if TDOT was forced to change the operation of this intersection by the councillor in question.

In particular, this sweeping generalisation really bothered me:

[Protected lefts are] are recognised internationally as the single safest way to manage a major intersection

The notion that protected-only phasing is always safer is total bollocks. Protected-only left turns naturally have less capacity than permissive lefts, and as a result of that, often have larger delays. As delays increase, drivers grow impatient and start doing things that drivers who were patient wouldn't do, like push yellow lights or follow too closely. What I see in Seattle (at protected lefts) quite often is drivers who turn left after the yellow arrow is expired (since they don't want to wait for another cycle), and nearly clip a pedestrian who entered the crosswalk, not expecting a driver to so blatantly ignore a red signal. I can't seem to find the study at the moment (I will find it and I will post it here soon), but one near me concluded that permissive lefts eventually prove safer because traffic levels improved, which as far as they could tell, reduced driver frustration, leading them to perform less risky maneuvers. I guess allowing drivers the liberty to turn in a gap is less risky than not!

[JKRhodes]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

They have a guy who changes out the signs twice a day... It's labor intensive, but it works great!

[ztonyg]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

They have a guy who changes out the signs twice a day... It's labor intensive, but it works great!

In all seriousness, I've seen this setup before where during periods of "protected only" operation the FYA never operates (only the green, yellow, and red arrows run during a cycle). During the "protected/permissive" operation, the FYA illuminates.

I'm interested to see how this operates with the sign. I can't imagine that anyone changes out the sign. So I'd guess that the FYA is switched off all the time and they run the 4 headed signal with only the green, yellow, and red arrow heads actually in operation.

[jakeroot]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

They have a guy who changes out the signs twice a day... It's labor intensive, but it works great!

In all seriousness, I've seen this setup before where during periods of "protected only" operation the FYA never operates (only the green, yellow, and red arrows run during a cycle). During the "protected/permissive" operation, the FYA illuminates.

I'm interested to see how this operates with the sign. I can't imagine that anyone changes out the sign. So I'd guess that the FYA is switched off all the time and they run the 4 headed signal with only the green, yellow, and red arrow heads actually in operation.

To the best of my knowledge, Tucson has been slowly adopting the flashing yellow arrow city-wide. It looks as though this intersection was converted before being converted again to protected only.

The setup that you (ztonyg) describe is referred to as TOD phasing, aka Time of Day phasing. This is common in some areas near me. I'm personally not the biggest fan.

[doorknob60]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

They have a guy who changes out the signs twice a day... It's labor intensive, but it works great!

In all seriousness, I've seen this setup before where during periods of "protected only" operation the FYA never operates (only the green, yellow, and red arrows run during a cycle). During the "protected/permissive" operation, the FYA illuminates.

Boise does this in a few places, generally during the evening rush. Pretty sure I've seen it in a few locations across Overland Rd, Fairview Ave, and possibly Franklin Rd (though less sure about that, a lot of the busier permissive ones are doghouses still). Usually restricting left turns from eastbound traffic turning against the heavy westbound direction. Pretty sure State St and Chinden (US-20/26) have some of these too, now that I think about it.

[JKRhodes]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

They have a guy who changes out the signs twice a day... It's labor intensive, but it works great!

In all seriousness, I've seen this setup before where during periods of "protected only" operation the FYA never operates (only the green, yellow, and red arrows run during a cycle). During the "protected/permissive" operation, the FYA illuminates.

I'm interested to see how this operates with the sign. I can't imagine that anyone changes out the sign. So I'd guess that the FYA is switched off all the time and they run the 4 headed signal with only the green, yellow, and red arrow heads actually in operation.

I just drove through the area again and was able to verify,  as was the case several months ago when I was last there, that the left turn signals at Speedway at Mountain, cherry, and Campbell all have the same configuration… Four headed signal with FYA and signage with verbiage of “left turn yield on flashing yellow arrow.”  The intersection at Campbell had an illuminated red arrow at the time ( 4 PM with heavy traffic)  which lends credence to the other poster's suggestion that the signal operates on TOD phasing
(edited... voice texting errors)

[ztonyg]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

They have a guy who changes out the signs twice a day... It's labor intensive, but it works great!

In all seriousness, I've seen this setup before where during periods of "protected only" operation the FYA never operates (only the green, yellow, and red arrows run during a cycle). During the "protected/permissive" operation, the FYA illuminates.

I'm interested to see how this operates with the sign. I can't imagine that anyone changes out the sign. So I'd guess that the FYA is switched off all the time and they run the 4 headed signal with only the green, yellow, and red arrow heads actually in operation.

I just drove through the area again and was able to verify,  as was the case several months ago when I was last there, that the left turn signals at Speedway at Mountain, cherry, and Campbell all have the same configuration… Four headed signal with FYA and signage with verbiage of “left turn yield on flashing yellow arrow.”  The intersection at Campbell had an illuminated red arrow at the time ( 4 PM with heavy traffic)  which lends credence to the other poster suggestion that the signal operates on TOD fission

I don't see how you can do TOD with this as the sign says "left on green arrow only".



I believe the FYA may simply be shut off.

[JKRhodes]

Does the new signal have 4 heads? I was just there recently... Speedway/Campbell, IIRC is protected only during peak hours, along with several other intersections along Speedway in the U of A corridor.

Non peak hours, the control is reverted to permissive/Protective (lag arrow) with a new FYA during the "Yield phase."

There is a 4 headed signal but underneath it there's a "left on green arrow only" sign which seems to mean that left turns wouldn't be permitted during a FYA "yield phase."

They have a guy who changes out the signs twice a day... It's labor intensive, but it works great!

In all seriousness, I've seen this setup before where during periods of "protected only" operation the FYA never operates (only the green, yellow, and red arrows run during a cycle). During the "protected/permissive" operation, the FYA illuminates.

I'm interested to see how this operates with the sign. I can't imagine that anyone changes out the sign. So I'd guess that the FYA is switched off all the time and they run the 4 headed signal with only the green, yellow, and red arrow heads actually in operation.

I just drove through the area again and was able to verify,  as was the case several months ago when I was last there, that the left turn signals at Speedway at Mountain, cherry, and Campbell all have the same configuration… Four headed signal with FYA and signage with verbiage of “left turn yield on flashing yellow arrow.”  The intersection at Campbell had an illuminated red arrow at the time ( 4 PM with heavy traffic)  which lends credence to the other poster suggestion that the signal operates on TOD fission

I don't see how you can do TOD with this as the sign says "left on green arrow only".



I believe the FYA may simply be shut off.

Again, the signage was not left on green arrow only yesterday when I drove through there. It was posted left turn yield on FYA in all four directions.

[jakeroot]

Is it possible they've already reverted it due to traffic issues? Also possible that "YIELD ON FYA..." was what they meant to install to limit operation by TOD, instead of all day.

[JKRhodes]

Is it possible they've already reverted it due to traffic issues? Also possible that "YIELD ON FYA..." was what they meant to install to limit operation by TOD, instead of all day.

Perhaps. I know it wasn't too long ago(as recently as last year) the intersection was set up with traditional 5-signal heads and lagging lefts. The KGUN 9 video may have been at the time of initial installation. Either the signage was installed in error, or the setup was reverted to TOD with FYA, because restricted lefts are so out of character for intersections within the city limits of Tucson.

[jakeroot]

I was checking out street view along Speedway (updated to June 2018), and the several double lefts along that stretch all appear to be operating how I was guessing above: TOD (time-of-day).

- During this busier shot at Campbell in June 2018 (during rush hour, I suppose), it is running protected-only: https://goo.gl/QyBGE4
- But, in this evening shot (late evening judging by position of sun and time of year), the signal is operating in permissive mode: https://goo.gl/xxPCKx
- Speedway itself lacks a lot of double lefts, but this one down at Alvernon was running permissive during the late-evening hour as well: https://goo.gl/axp9BG

I think this compromise is acceptable, as it probably does improve pedestrian safety. That said, I am curious how it has impacted traffic.

roadiejay, since you live in the area, couple of questions: (1) how is traffic coping with the new phasing style? Are left turns heavier than before? And (2) are my predictions above true? Does it run with TOD phasing?

[Roadwarriors79]

The signs at Speedway and Campbell now say "Left turn yield on flashing yellow arrow". All the left turn signals on Speedway between Main Ave (just east of I-10) to Alvernon Way look like they have been converted on GSV.

[jakeroot]

The signs at Speedway and Campbell now say "Left turn yield on flashing yellow arrow". All the left turn signals on Speedway between Main Ave (just east of I-10) to Alvernon Way look like they have been converted on GSV.

Evidently, the signs in the video were mistakenly installed.

[JKRhodes]

I was checking out street view along Speedway (updated to June 2018), and the several double lefts along that stretch all appear to be operating how I was guessing above: TOD (time-of-day).

- During this busier shot at Campbell in June 2018 (during rush hour, I suppose), it is running protected-only: https://goo.gl/QyBGE4
- But, in this evening shot (late evening judging by position of sun and time of year), the signal is operating in permissive mode: https://goo.gl/xxPCKx
- Speedway itself lacks a lot of double lefts, but this one down at Alvernon was running permissive during the late-evening hour as well: https://goo.gl/axp9BG

I think this compromise is acceptable, as it probably does improve pedestrian safety. That said, I am curious how it has impacted traffic.

roadiejay, since you live in the area, couple of questions: (1) how is traffic coping with the new phasing style? Are left turns heavier than before? And (2) are my predictions above true? Does it run with TOD phasing?

Yes, it runs with TOD phasing. I spent several weeks in the area late last year and early this year when my daughter was hospitalized at Banner-UMC, and that was the case then. Honestly I don't think it affects the traffic much at all. If anything, it might hold up the lagging left turns by about a half a second during rush hour since traffic is so heavy, it's impossible to turn when thru traffic has a green. So by the time the arrow comes on, turning traffic has to start from the stop bar instead of where they used to previously hang out in the middle of the intersection.

In the interest of full disclosure: I moved to Utah six weeks ago. Last time I was in the area of speedway and campbell was July of 2018. But as with early this year, it was a FYA with TOD phasing,as other posters have confirmed since your last reply. Cheers!

[jakeroot]

Yes, it runs with TOD phasing. I spent several weeks in the area late last year and early this year when my daughter was hospitalized at Banner-UMC, and that was the case then. Honestly I don't think it affects the traffic much at all. If anything, it might hold up the lagging left turns by about a half a second during rush hour since traffic is so heavy, it's impossible to turn when thru traffic has a green. So by the time the arrow comes on, turning traffic has to start from the stop bar instead of where they used to previously hang out in the middle of the intersection.

Thank you for the info. Hope all is well with your kid.

Yeah, I noticed when I was there last December that, for the most part during busy times, there was never a gap. So while traffic was free to pull forward, a green arrow was needed to get a decent number of cars through the intersection. Part of me prefers this method, as it gets a few more cars out of each cycle (cars behind stop line + those waiting out in the intersection, rather than just the former), but it's not a major change, and if there's a problem with cars performing risky maneuvers (due to impatience or whatever), this would help.

In the interest of full disclosure: I moved to Utah six weeks ago. Last time I was in the area of speedway and campbell was July of 2018. But as with early this year, it was a FYA with TOD phasing,as other posters have confirmed since your last reply. Cheers!

Nice! Beautiful state. Probably a nice change from the Tucson scenery. I only enjoy Tucson because of the traffic lights. Without them...not sure I'd like the city too much!

[Roadwarriors79]

At times, I wish Tucson would reconsider either the lagging left at every intersection or not using protected lefts at more intersections. Granted, the city has changed a few of the intersections since I was living there. One I would hope gets adjustments at some point is where Grant Road, Kolb Road, and Tanque Verde Road meet. One direction (going from Grant EB to Tanque Verde EB) gets heavy left turn traffic, while the other direction (Kolb NB to Tanque Verde WB) has significantly less left turn traffic.

https://www.google.com/maps/@32.2481986,-110.849904,3a,75y,343.51h,64.43t/data=!3m7!1e1!3m5!1sxNE_zWPRXqpWro1fIYId6w!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3DxNE_zWPRXqpWro1fIYId6w%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D96%26h%3D64%26yaw%3D304.51367%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656

I have noticed that Tucson has gone from mostly using median left turn signals at major intersections to mostly overhead and far side left turn signals at the newer installations.

[jakeroot]

As long as they remain well-designed, I'm not opposed to double permissive left turns. I'm sure you know my position on them. But I would like to see them changed to flashing yellow arrows with protected phasing by time of day.

[Roadwarriors79]

What do you think of the indirect left turns or "Michigan lefts" planned or in use along Grant Road? The major north-south streets (Oracle Road, 1st Avenue, and others) still have permissive dual lefts for the NB-to-WB and SB-to-EB movements.

[jakeroot]

What do you think of the indirect left turns or "Michigan lefts" planned or in use along Grant Road? The major north-south streets (Oracle Road, 1st Avenue, and others) still have permissive dual lefts for the NB-to-WB and SB-to-EB movements.

I like it! Creates an opportunity for a mid-block crossing for pedestrians, and reduces the number of phases at the primary intersection. Definitely improves corridor progression. I hope they remain as flashing yellow arrows.