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Regional Boards => Mountain West => Topic started by: Roadwarriors79 on April 03, 2018, 12:37:17 PM

Title: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on April 03, 2018, 12:37:17 PM
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.

https://www.youtube.com/watch?v=Sc8cYOTYIt8
Title: Re: Protected Left Turns in Tucson AZ
Post by: i-215 on April 04, 2018, 07:47:18 PM
Wait...  a permissive dual left turn?  How on earth does that work?    :wow:

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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: roadfro on April 05, 2018, 03:58:12 PM
Quote from: i-215 on April 04, 2018, 07:47:18 PM
Wait...  a permissive dual left turn?  How on earth does that work?    :wow:

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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: kdk on April 11, 2018, 06:01:04 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on April 17, 2018, 08:01:58 PM
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."
Title: Re: Protected Left Turns in Tucson AZ
Post by: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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."
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on April 18, 2018, 06:40:02 PM
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:

Quote from: Steve Kozachik, Tucson City Councillor (0:46 in YouTube Clip)
[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!
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on April 18, 2018, 11:09:58 PM
Quote from: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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!
Title: Re: Protected Left Turns in Tucson AZ
Post by: ztonyg on April 19, 2018, 10:54:41 AM
Quote from: roadiejay on April 18, 2018, 11:09:58 PM
Quote from: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on April 19, 2018, 11:29:08 AM
Quote from: ztonyg on April 19, 2018, 10:54:41 AM
Quote from: roadiejay on April 18, 2018, 11:09:58 PM
Quote from: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: doorknob60 on April 20, 2018, 04:07:43 PM
Quote from: ztonyg on April 19, 2018, 10:54:41 AM
Quote from: roadiejay on April 18, 2018, 11:09:58 PM
Quote from: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on April 21, 2018, 07:41:53 PM
Quote from: ztonyg on April 19, 2018, 10:54:41 AM
Quote from: roadiejay on April 18, 2018, 11:09:58 PM
Quote from: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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)
Title: Re: Protected Left Turns in Tucson AZ
Post by: ztonyg on April 21, 2018, 08:08:28 PM
Quote from: roadiejay on April 21, 2018, 07:41:53 PM
Quote from: ztonyg on April 19, 2018, 10:54:41 AM
Quote from: roadiejay on April 18, 2018, 11:09:58 PM
Quote from: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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".

(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi65.tinypic.com%2F263fnsk.jpg&hash=d6c2728c503654c9a86b9538510809953499025b)

I believe the FYA may simply be shut off.

Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on April 22, 2018, 02:31:04 PM
Quote from: ztonyg on April 21, 2018, 08:08:28 PM
Quote from: roadiejay on April 21, 2018, 07:41:53 PM
Quote from: ztonyg on April 19, 2018, 10:54:41 AM
Quote from: roadiejay on April 18, 2018, 11:09:58 PM
Quote from: ztonyg on April 18, 2018, 05:56:12 PM
Quote from: roadiejay on April 17, 2018, 08:01:58 PM
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".

(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi65.tinypic.com%2F263fnsk.jpg&hash=d6c2728c503654c9a86b9538510809953499025b)

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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on April 22, 2018, 03:44:59 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on April 22, 2018, 05:35:39 PM
Quote from: jakeroot on April 22, 2018, 03:44:59 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on October 17, 2018, 08:03:02 PM
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?
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on October 19, 2018, 05:54:57 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on October 19, 2018, 08:01:11 PM
Quote from: Roadwarriors79 on October 19, 2018, 05:54:57 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on October 21, 2018, 02:09:35 AM
Quote from: jakeroot on October 17, 2018, 08:03:02 PM
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!
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on October 21, 2018, 02:39:14 AM
Quote from: roadiejay on October 21, 2018, 02:09:35 AM
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.

Quote from: roadiejay on October 21, 2018, 02:09:35 AM
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!
:cheers:
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on October 21, 2018, 12:50:54 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on October 21, 2018, 01:14:22 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on October 21, 2018, 03:08:03 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on October 21, 2018, 03:12:51 PM
Quote from: Roadwarriors79 on October 21, 2018, 03:08:03 PM
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.
Title: Re: Protected Left Turns in Tucson AZ
Post by: DJStephens on November 01, 2018, 10:22:30 PM
Quote from: Roadwarriors79 on October 21, 2018, 03:08:03 PM
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.

Saw them in construction during May and June while doing asphalt sampling and coring for a geotechnical firm.  They require a substantial amount of additional area in the form of a "bulb out" in order to allow large vehicles to U turn.  Also create additional signals and delays for E-W Grant traffic.   Suspect that these are experimental and will not be duplicated elsewhere in Tucson.
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on November 02, 2018, 12:06:03 PM
Quote from: DJStephens on November 01, 2018, 10:22:30 PM
Quote from: Roadwarriors79 on October 21, 2018, 03:08:03 PM
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.

Saw them in construction during May and June while doing asphalt sampling and coring for a geotechnical firm.  They require a substantial amount of additional area in the form of a "bulb out" in order to allow large vehicles to U turn.  Also create additional signals and delays for E-W Grant traffic.   Suspect that these are experimental and will not be duplicated elsewhere in Tucson.

Other than the major intersections and Grant (which may or may not include Swan Rd), the only other one under construction is at Kolb Rd and Valencia Rd. This is an intersection that I think would have been better served with a grade-separated interchange, or at least a flyover ramp. The heaviest turn movements are EB Valencia to NB Kolb, and SB Kolb to WB Valencia.
Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on November 03, 2018, 04:37:43 AM
Quote from: DJStephens on November 01, 2018, 10:22:30 PM
Suspect that these are experimental and will not be duplicated elsewhere in Tucson.

Probably right. These work very well as part of a coordinated corridor (MI has many examples), but only OK at single-use intersections like here.
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on November 03, 2018, 11:18:36 AM
I don't know if the "Michigan lefts" will get Grant Rd widened any sooner or not. I have seen schematics for future widening projects planned on Broadway (from Euclid Ave to Country Club Rd) and 22nd St (from I-10 to Tucson Blvd). The widened roads would have dual left turn lanes at intersections with other major streets.
Title: Re: Protected Left Turns in Tucson AZ
Post by: DJStephens on November 03, 2018, 12:48:58 PM
The Grant Road project that I was on was Phase II (Stone to Park). It was being reconstructed as a four lane divided arterial.   The ROW appeared wide enough to go six lanes, but do not believe maximum width was a goal of either Phase I or II.   Pedestrian safety, bus pull outs and complete curb and guttering seemed to be the goal.     
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on November 03, 2018, 01:24:36 PM
Quote from: DJStephens on November 03, 2018, 12:48:58 PM
The Grant Road project that I was on was Phase II (Stone to Park). It was being reconstructed as a four lane divided arterial.   The ROW appeared wide enough to go six lanes, but do not believe maximum width was a goal of either Phase I or II.   Pedestrian safety, bus pull outs and complete curb and guttering seemed to be the goal.   

It will be six lanes (eventually). Check out this video (near the end of construction of the Stone-to-Park segment):

https://www.youtube.com/watch?v=Oygo-T4oMP0&feature=youtu.be
Title: Re: Protected Left Turns in Tucson AZ
Post by: tradephoric on November 03, 2018, 03:22:32 PM
^That video of Grant Road does appear to be the first Median U-Turn corridor outside of Michigan.  Now the side-streets still allow direct lefts onto Grant Road so it's not exactly what you would see in Michigan (where all left turns are restricted at the main intersection).  A Median U-turn corridor is really a combination of the two intersection designs below (which is basically what you see in that Grant Road video).  Now the Median U-turn corridor along Grant Road only appears to last a few miles where in Michigan the longest Median U-turn corridor extends over 30 miles along Telegraph Road.. but it's a start!

(https://safety.fhwa.dot.gov/intersection/innovative/uturn/images/image001-left-lgr.jpg)

(https://safety.fhwa.dot.gov/intersection/innovative/uturn/images/image002-right-lgr.jpg)

Here's a video all about Median U-turn corridors.  The guy at 2:30 talking about Woodward avenue who says "you can make it down Woodward quite quickly" isn't lying.  To prove it, I posted a video of a 40 mile drive down Woodward avenue driving BOTH directions, traveling through 124 traffic signals without getting stopped at a single red light.  Say what you want about Michigan lefts, but they really do help with good signal progression along the corridor.

https://www.youtube.com/watch?v=rvazA22vhN0

https://www.youtube.com/watch?v=mb2R2fPB1nE



Title: Re: Protected Left Turns in Tucson AZ
Post by: jakeroot on November 03, 2018, 05:34:18 PM
Quote from: tradephoric on November 03, 2018, 03:22:32 PM
Now the Median U-turn corridor along Grant Road only appears to last a few miles where in Michigan the longest Median U-turn corridor extends over 30 miles along Telegraph Road.. but it's a start!

The thing that MI will always have, that very few other jurisdictions ever will, is infinitely-wide ROWs. The widest roads in my area rarely crack 120 feet in width (curb to curb). Telegraph seems to sit around 150 to 160 feet. That extra room permits, among other things, half of the U-turn maneuver to occur in the median, so as to not require bulb-outs, which are often required at non-MI Median U-turn intersections.

That said, I think some of the bulb-outs are unnecessarily large (those along Grant, above, for example). A truck needing that much room to turn around, may as well be allowed to turn left at the intersection, or (if leaving a parking lot and being forced to turn right), turn left onto another road and come back. A corridor with thousands of trucks should probably just use standard lefts.

Pierce County, WA has built several roads that use U-turns to facilitate some movements. Canyon Road, which has quite a few normal lefts but many U-turn lefts for side streets, doesn't have any bulb-outs (https://goo.gl/DdCocH) because there's three lanes for through traffic, but another (176 St) has bulb-outs (https://goo.gl/hUqQhC), though they are much smaller than those built in Tucson, for example. I have seen trucks perform U-turns along these corridors (it's not a quick process), but it's very rare.
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on September 10, 2020, 10:07:26 PM
The major east side intersections (22nd, Broadway, Speedway at Kolb, Wilmot, Craycroft, etc) have all gone to four head FYA left turn signals with TOD phasing as of my last visit.

In my observation the left turn signal tends to stay red until the queue of through traffic clears the intersection. Then it transitions to FYA, followed by a lagging green arrow as they've historically operated.

The five-head FYA for right turns still remain at intersections where they were previously installed. Odd to see a "tucson experimental" signal treatment and a new MUTCD standard being used at the same intersections.
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on October 24, 2022, 01:18:17 AM
Stayed in Chandler, AZ over the weekend and noticed several intersections with four aspect FYA heads and permissive left turns for dual left turn lanes near the mall.

I figured most cities in the valley would be distancing themselves from "tucson permissive dual lefts", not adopting them.
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on October 24, 2022, 07:40:00 PM
Quote from: JKRhodes on October 24, 2022, 01:18:17 AM
Stayed in Chandler, AZ over the weekend and noticed several intersections with four aspect FYA heads and permissive left turns for dual left turn lanes near the mall.

I figured most cities in the valley would be distancing themselves from "tucson permissive dual lefts", not adopting them.

Most valley cities do not do what Tucson historically does, at least not all the time. Most of the dual lefts in Chandler that have FYA are on time-of-day phasing. Other than a few intersections in Peoria, most of the valley has stuck with standard protected dual left signals.
Title: Re: Protected Left Turns in Tucson AZ
Post by: JKRhodes on October 24, 2022, 08:42:56 PM
Quote from: Roadwarriors79 on October 24, 2022, 07:40:00 PM
Quote from: JKRhodes on October 24, 2022, 01:18:17 AM
Stayed in Chandler, AZ over the weekend and noticed several intersections with four aspect FYA heads and permissive left turns for dual left turn lanes near the mall.

I figured most cities in the valley would be distancing themselves from "tucson permissive dual lefts", not adopting them.

Most valley cities do not do what Tucson historically does, at least not all the time. Most of the dual lefts in Chandler that have FYA are on time-of-day phasing. Other than a few intersections in Peoria, most of the valley has stuck with standard protected dual left signals.

That's a good point. I was also in Tucson recently and noticed most intersections on the east side had gone to 4-aspect FYA with TOD phasing. Traffic was heavy enough at the time  that many of the left turns never saw a permissive phase. By my observations there is only a handful of five aspect permissive/protected dual lefts  remaining in Tucson. One intersection (I wanna say speedway and alvernon) had a 5 aspect signal with dual lefts for one street and a four aspect FYA head with TOD phasing for the other road.  Odd to see a partial upgrade. So I guess what I find appealing is that we're going to start seeing a little more consistency across the map as the FYA with TOD becomes more widely implemented.

Tucson still isn't without its quirks; they have the five aspect signal with FYA for right turns on red which has historically meant yield to u-turns on the cross road which has a green left arrow and no restrictions on U-turns. During my most recent trip, traveling down the newly widened stretch of broadway between country club and Euclid, I noticed this aspect was also displayed during the through green phase. Not sure what the meaning was other than "right turns yield to pedestrians"  which is already implied during a green through phase.

There's a 5-way intersection downtown with a 5 aspect left turn signal and a FYA for lefts, which is used to indicate that  oncoming traffic has a red, but you still need to yield to pedestrians.

I feel bad for Tucson drivers constantly having to deduce the meaning of their local FYA signals.
Title: Re: Protected Left Turns in Tucson AZ
Post by: machias on October 25, 2022, 09:45:30 AM
Quote from: JKRhodes on October 24, 2022, 08:42:56 PM
Quote from: Roadwarriors79 on October 24, 2022, 07:40:00 PM
Quote from: JKRhodes on October 24, 2022, 01:18:17 AM
Stayed in Chandler, AZ over the weekend and noticed several intersections with four aspect FYA heads and permissive left turns for dual left turn lanes near the mall.

I figured most cities in the valley would be distancing themselves from "tucson permissive dual lefts", not adopting them.

Most valley cities do not do what Tucson historically does, at least not all the time. Most of the dual lefts in Chandler that have FYA are on time-of-day phasing. Other than a few intersections in Peoria, most of the valley has stuck with standard protected dual left signals.

That's a good point. I was also in Tucson recently and noticed most intersections on the east side had gone to 4-aspect FYA with TOD phasing. Traffic was heavy enough at the time  that many of the left turns never saw a permissive phase. By my observations there is only a handful of five aspect permissive/protected dual lefts  remaining in Tucson. One intersection (I wanna say speedway and alvernon) had a 5 aspect signal with dual lefts for one street and a four aspect FYA head with TOD phasing for the other road.  Odd to see a partial upgrade. So I guess what I find appealing is that we're going to start seeing a little more consistency across the map as the FYA with TOD becomes more widely implemented.

Tucson still isn't without its quirks; they have the five aspect signal with FYA for right turns on red which has historically meant yield to u-turns on the cross road which has a green left arrow and no restrictions on U-turns. During my most recent trip, traveling down the newly widened stretch of broadway between country club and Euclid, I noticed this aspect was also displayed during the through green phase. Not sure what the meaning was other than "right turns yield to pedestrians"  which is already implied during a green through phase.

There's a 5-way intersection downtown with a 5 aspect left turn signal and a FYA for lefts, which is used to indicate that  oncoming traffic has a red, but you still need to yield to pedestrians.

I feel bad for Tucson drivers constantly having to deduce the meaning of their local FYA signals.

I've lived in Tucson for a little over 18 months. I'm still blown away with how signals are configured here. Tucson really loves its FYA. Some signal installations aren't even in sync, so each FYA is flashing at its own pace. And the dual lane left turns where there's very little sight line to oncoming traffic is especially interesting. The city really does its own thing when interpreting the MUTCD. And don't get me started on the awful overhead signing the city installed a year or two ago.
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on October 25, 2022, 02:22:11 PM
Tucson having a lot of "quirks" is pretty accurate. Even more noticeable since the other agencies in the area (Oro Valley, Marana, ADOT, Pima County DOT) all tend to be more conventional. Keep things simple whenever possible.

Something loosely related, I always wondered how Tucson, which seems to hate most freeways and highways, managed to get a state highway number that actually makes sense (AZ 210) while the Phoenix area seems to have a bunch of random numbers for their newer freeways.
Title: Re: Protected Left Turns in Tucson AZ
Post by: Roadwarriors79 on October 25, 2022, 02:28:37 PM
Speaking of left turns, it looks like for the Grant Road widening, the intersections at Swan and Country Club are going to remain conventional intersections after widening. So the only other "Michigan lefts" planned in this corridor are at Alvernon and Campbell.
Title: Re: Protected Left Turns in Tucson AZ
Post by: Tendies on November 04, 2022, 04:53:41 PM
Quote from: Roadwarriors79 on October 24, 2022, 07:40:00 PM
Quote from: JKRhodes on October 24, 2022, 01:18:17 AM
Stayed in Chandler, AZ over the weekend and noticed several intersections with four aspect FYA heads and permissive left turns for dual left turn lanes near the mall.

I figured most cities in the valley would be distancing themselves from "tucson permissive dual lefts", not adopting them.

Most valley cities do not do what Tucson historically does, at least not all the time. Most of the dual lefts in Chandler that have FYA are on time-of-day phasing. Other than a few intersections in Peoria, most of the valley has stuck with standard protected dual left signals.
Most of the dual FYA lights in Peoria are at places where a major road dead ends into a residential road or parking lot. In these cases, actually having to yield on the yellow arrow almost never happens, as most traffic coming out the other side is usually either turning right (usually on red), or left. More often than not though the FYA doesnt even need to come on, as there is no need for the other side's straight through to even turn green. The one car that does go straight every hour or so gets to go before the other side gets the FYA. There are rare cases where a car going straight approaches an already green light with traffic still turning left on FYA, which can cause issues, however I've seen this happen on single lefts, and even still this hardly ever happens (83 x peoria, peoria x grand, rio vista x thunderbird, 83 x LPP)
https://www.google.com/maps/@33.5816602,-112.2363858,3a,37.5y,54.95h,89.34t/data=!3m6!1e1!3m4!1ss043bHS6Unfm92jlIeM-5Q!2e0!7i16384!8i8192

We do have a diamond interchange (AZ-303 and LPP) which uses a 5 section green circle for permissive lefts with double turn lanes, however its so low volume that the double lanes are completely pointless at this intersection. Diamond interchanges are perfect for dual permissive lefts, as they dont suffer from visibility problems that normal intersections have. Theres another one with the same setup over at northern parkway and sarival in Surprise. Far West valley (especially Peoria) is known for overbuilding the - out of everything.
https://www.google.com/maps/@33.7704339,-112.2497679,3a,28y,352.02h,88.4t/data=!3m6!1e1!3m4!1s_rLk_i7PKSdtFecMPdso3Q!2e0!7i16384!8i8192

Even stranger is that we have two intersections (75 x cactus, 75 x peoria) that were converted from single left on yield to double protected a few years ago, but they installed an FYA signal head that never gets used. It malfunctioned one day two years ago and actually gave the FYA, but it was fixed the next day. These intersections dont even need double lefts anyway. Its not uncommon to see only 5 or so cars turning left even during rush hour. Also cycles are long in peoria, so theres plenty of time with ample gaps in traffic, but nope. There is no TOD phasing either, as its still red even as late as 3:00 am! Double lefts look better on paper, so double left it is!
https://www.google.com/maps/@33.5958479,-112.2197099,3a,37.5y,276.27h,87.54t/data=!3m6!1e1!3m4!1sO7KDIYGRKcVMLf0oKpXgoQ!2e0!7i16384!8i8192
Title: Re: Protected Left Turns in Tucson AZ
Post by: DJStephens on November 05, 2022, 11:58:30 AM
Quote from: Roadwarriors79 on October 25, 2022, 02:22:11 PM
Tucson having a lot of "quirks" is pretty accurate. Even more noticeable since the other agencies in the area (Oro Valley, Marana, ADOT, Pima County DOT) all tend to be more conventional. Keep things simple whenever possible.

Something loosely related, I always wondered how Tucson, which seems to hate most freeways and highways, managed to get a state highway number that actually makes sense (AZ 210) while the Phoenix area seems to have a bunch of random numbers for their newer freeways.

If you mean that "AZ 210" makes sense, in the sense of it possibly being an Interstate number, it does in terms of being "close" to it's parent, but a 210 number it should have been further west.   In Phoenix metro perhaps.    Personally would have used "810" instead of "210" as Tucson is farther East in the state.   What was the Tucson planning mentality, back in the day?  Take the Federal allotments, (10 & 19) and not plan for anything else?   No one saw the writing on the wall?  Meaning increased growth, and transplants?  Very similar to Albuquerque in some ways. Yep, Phoenix seems to have had the same problem as well, it took a Maricopa County sales tax approval in the mid eighties to get the loops there we have today.