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Author Topic: Protected Left Turns in Tucson AZ  (Read 9871 times)

DJStephens

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Re: Protected Left Turns in Tucson AZ
« Reply #25 on: November 01, 2018, 10:22:30 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.
« Last Edit: November 01, 2018, 10:28:12 PM by DJStephens »
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Roadwarriors79

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Re: Protected Left Turns in Tucson AZ
« Reply #26 on: November 02, 2018, 12:06:03 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.
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jakeroot

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Re: Protected Left Turns in Tucson AZ
« Reply #27 on: November 03, 2018, 04:37:43 AM »

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.

Roadwarriors79

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Re: Protected Left Turns in Tucson AZ
« Reply #28 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.
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DJStephens

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Re: Protected Left Turns in Tucson AZ
« Reply #29 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.     
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Roadwarriors79

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Re: Protected Left Turns in Tucson AZ
« Reply #30 on: November 03, 2018, 01:24:36 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):

« Last Edit: November 03, 2018, 09:19:10 PM by Roadwarriors79 »
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tradephoric

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Re: Protected Left Turns in Tucson AZ
« Reply #31 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!





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.





« Last Edit: November 03, 2018, 03:40:41 PM by tradephoric »
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jakeroot

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Re: Protected Left Turns in Tucson AZ
« Reply #32 on: November 03, 2018, 05:34:18 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 because there's three lanes for through traffic, but another (176 St) has bulb-outs, 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.

JKRhodes

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Re: Protected Left Turns in Tucson AZ
« Reply #33 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.
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JKRhodes

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Re: Protected Left Turns in Tucson AZ
« Reply #34 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.
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Roadwarriors79

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Re: Protected Left Turns in Tucson AZ
« Reply #35 on: October 24, 2022, 07:40:00 PM »

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.
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JKRhodes

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Re: Protected Left Turns in Tucson AZ
« Reply #36 on: October 24, 2022, 08:42:56 PM »

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.
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machias

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Re: Protected Left Turns in Tucson AZ
« Reply #37 on: October 25, 2022, 09:45:30 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.
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Roadwarriors79

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Re: Protected Left Turns in Tucson AZ
« Reply #38 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.
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Roadwarriors79

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Re: Protected Left Turns in Tucson AZ
« Reply #39 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.
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Tendies

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Re: Protected Left Turns in Tucson AZ
« Reply #40 on: November 04, 2022, 04:53:41 PM »

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
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DJStephens

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Re: Protected Left Turns in Tucson AZ
« Reply #41 on: November 05, 2022, 11:58:30 AM »

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.   
« Last Edit: December 17, 2022, 10:55:02 AM by DJStephens »
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