AARoads Forum

In my opinion, one of the most interesting things about roads is the variety of ways in which left turns are handled.  For the purpose of this topic, I'm limiting poll choices to controlled left turns--i.e., left turns that are either signalized and not entirely unprotected, or left turns that are separated from the mainline or handled via an alternative roadway design treatment (which can include roundabouts).  Probably the best answer would be "It depends on the context," but if you can sum it up to relatively generalizable conditions, what would be your preferred method?

Personally, I'll admit that for a long time I've been fascinated with jughandles, but I can see their disadvantages, mostly the amount of real estate they use.  I tend to wonder if this is the main reason they're not very common outside of New Jersey and Pennsylvania (several other states have a handful here and there, but they're not common enough to be typical intersection designs in most states).  I also really wonder how other road enthusiasts and experts prefer to see left turns treated on arterial highways and at signalized intersections on expressways.  Do you prefer a traditional protected/permissive or protected-only signal with as many phases as necessary, or do you prefer the way they're often handled in Michigan and/or New Jersey?  And why?

And, of course, one of the poll options is "No Left Turn--Find Your Own Way!" (one of too many examples to list: https://goo.gl/maps/cpV9XigTLxGp4iXR8 ).  Does anyone think this approach is generally warranted, would you rather see signs telling drivers how to make the connection, or would you rather slow down through traffic with an extra signal phase?

Signals should be two phases if possible unless it's a 5-way (or more) intersection. I voted for forward jughandle, but Michigan lefts also work. Left turns can be prohibited entirely if there's an easy way to get to the same place (e.g. turning left at the previous signal) or if turning right earlier enables you to go straight across later, making an effective left turn.

Quote from: 1 on April 08, 2021, 10:39:08 AM
Signals should be two phases if possible unless it's a 5-way (or more) intersection.

Does this mean green arrows should not exist?

Here is an example (https://www.google.com/maps/@43.0768397,-77.522353,3a,44.9y,170.96h,79.25t/data=!3m6!1e1!3m4!1sBnIx16XbJLFuzueJ3ocmpg!2e0!7i16384!8i8192!5m1!1e1) of a roughly K-shaped intersection where each of the four directions has their own phase. Four phases total, but no arrows. I get why this setup is used here, but it makes for some very long red lights.

What about requiring left turns to be made from the frontage road?

Quote from: kphoger on April 08, 2021, 11:32:22 AM
What about requiring left turns to be made from the frontage road?

Like in a multi-way boulevard?  I haven't seen a lot of good examples.  Although, there is this one in Kansas City, which seems kind of awkward and involves two very closely spaced traffic signals, but it works: https://goo.gl/maps/p5VoigVqDiW7zPuT9

Quote from: webny99 on April 08, 2021, 10:46:31 AM

Quote from: 1 on April 08, 2021, 10:39:08 AM
Signals should be two phases if possible unless it's a 5-way (or more) intersection.

Does this mean green arrows should not exist?

Here is an example (https://www.google.com/maps/@43.0768397,-77.522353,3a,44.9y,170.96h,79.25t/data=!3m6!1e1!3m4!1sBnIx16XbJLFuzueJ3ocmpg!2e0!7i16384!8i8192!5m1!1e1) of a roughly K-shaped intersection where each of the four directions has their own phase. Four phases total, but no arrows. I get why this setup is used here, but it makes for some very long red lights.

If possible. Quite a lot of signals, likely over half, can't become two-phase easily.

Quote from: stridentweasel on April 08, 2021, 12:05:31 PM

Quote from: kphoger on April 08, 2021, 11:32:22 AM
What about requiring left turns to be made from the frontage road?

Like in a multi-way boulevard?  I haven't seen a lot of good examples.  Although, there is this one in Kansas City, which seems kind of awkward and involves two very closely spaced traffic signals, but it works: https://goo.gl/maps/p5VoigVqDiW7zPuT9

Didn't North Avenue (IL-64) use to have a section or two like this?  I can't seem to find it on GSV right now, but maybe they got rid of that.

At any rate, I've encountered this type of traffic control in Mexico.  Here are three such left turns I've personally done:  example 1 (https://goo.gl/maps/dx5bLvSJngsKSu2Z7), example 2 (https://goo.gl/maps/JNwEzBZLRCiNr1y48), example 3 (https://goo.gl/maps/3fd15JVRVhTMMBDJ7).

Quote from: kphoger on April 08, 2021, 12:47:17 PM
At any rate, I've encountered this type of traffic control in Mexico.  Here are three such left turns I've personally done:  example 1 (https://goo.gl/maps/dx5bLvSJngsKSu2Z7), example 2 (https://goo.gl/maps/JNwEzBZLRCiNr1y48), example 3 (https://goo.gl/maps/3fd15JVRVhTMMBDJ7).

Interesting!  I'd call those multi-way boulevards, although The Boulevard Book advises against using slip lanes to access the frontage roadways, which makes me wonder, if you're going to require use of the frontage roads for all turns, is there really a better alternative?

I'm not sure if there's an area that actually does this, but in high traffic/pedestrian areas, you could use a FYA and use it as a protective only during peak times, and switch on the flashing yellow function at other times.

In low density residential areas, roundabouts are my preferred type.

Quote from: 1 on April 08, 2021, 12:11:12 PM

Quote from: webny99 on April 08, 2021, 10:46:31 AM

Quote from: 1 on April 08, 2021, 10:39:08 AM
Signals should be two phases if possible unless it's a 5-way (or more) intersection.

Does this mean green arrows should not exist?

If possible. Quite a lot of signals, likely over half, can't become two-phase easily.

What are some examples of signals with more than two phases that could be reduced to two? Most that I can think of that have four need all four.

Quote from: webny99 on April 08, 2021, 01:15:31 PM

Quote from: 1 on April 08, 2021, 12:11:12 PM

Quote from: webny99 on April 08, 2021, 10:46:31 AM

Quote from: 1 on April 08, 2021, 10:39:08 AM
Signals should be two phases if possible unless it's a 5-way (or more) intersection.

Does this mean green arrows should not exist?

If possible. Quite a lot of signals, likely over half, can't become two-phase easily.

What are some examples of signals with more than two phases that could be reduced to two? Most that I can think of that have four need all four.

Take MA 114 and MA 133 in North Andover, for example. Very few people should be turning left from 133, both eastbound and westbound, since there's a faster connector (MA 125 on one side, Waverley Rd./High St. on the other). While the lefts are permissive here, if they would have to be upgraded to protected, they should be banned entirely so it can be 3 phases instead of 4.

I would even say ban them now; while it doesn't save a phase, it still reduces crashes.

Quote from: webny99 on April 08, 2021, 01:15:31 PM
What are some examples of signals with more than two phases that could be reduced to two? Most that I can think of that have four need all four.

Tell that to Chicago (https://goo.gl/maps/JFxrUzBovZbZ4pw76) (intersection chosen at random).

Left turns are one of my favorite things to discuss.

I prefer regular left turns. I find alternative designs, like median U-turns or jug-handles, take too much land and aren't always as friendly to pedestrians.

In terms of the US: I quite like Tucson. I think their street network and traffic operations are pretty much perfect: green arrows at the end, red arrows to protect pedestrians during the beginning of the phase, permissive phasing otherwise, even at double left turns.

An engineer near me once claimed "the best left turn is a skipped left turn". In other words: default to permissive.

Quote from: kphoger on April 08, 2021, 01:59:17 PM

Quote from: webny99 on April 08, 2021, 01:15:31 PM
What are some examples of signals with more than two phases that could be reduced to two? Most that I can think of that have four need all four.

Tell that to Chicago (https://goo.gl/maps/JFxrUzBovZbZ4pw76) (intersection chosen at random).

Is that an intersection that needs more than two phases? I don't see why. Unless there are insane backups at rush hour.

I am personally of the opinion that through traffic is far more important than turning traffic. Adding left turn phasing to intersections that don't absolutely need it reduces the amount of time given to through traffic, which can place a bigger burden on other nearby intersections.

Quote from: jakeroot on April 08, 2021, 02:20:11 PM
Left turns are one of my favorite things to discuss.

I prefer regular left turns. I find alternative designs, like median U-turns or jug-handles, take too much land and aren't always as friendly to pedestrians.

Jughandles do take up a lot of land, and slip ramps aren't the safest things to cross on foot.  Although, in New Jersey, you'll often find that jughandles tend to be on highways that don't have sidewalks to begin with, but sometimes, yes, they do have to cross a sidewalk.  As for median U-turns, the variety that they use in Michigan typically involve roads with a huge right-of-way, but in those cases, the U-turns don't extend beyond the right-of-way (one might infer that the width was designed to accommodate them).

Quote
In terms of the US: I quite like Tucson. I think their street network and traffic operations are pretty much perfect: green arrows at the end, red arrows to protect pedestrians during the beginning of the phase, permissive phasing otherwise, even at double left turns.

It's worth noting that Tucson has started using downstream U-turns similar to the Michigan left concept, although the ones I know of in Tucson involve loons rather than extra-wide medians.  Examples: https://goo.gl/maps/awya3hGXVpjddaf5A

Quote
An engineer near me once claimed "the best left turn is a skipped left turn". In other words: default to permissive.

I'm not sure I fully understand the quotation.  "Skipped" as in, the signal has the ability to skip the protected phase?

Which application do you feel works best for signalized intersections on expressways?  Especially expressways that transition from and between freeways?  (And before somebody says "Expressways shouldn't have traffic signals," I understand the sentiment, but that's not the topic at hand, and in the real world, they often do.)  Would you still stick to traditional intersections with protected/permissive phasing?  Here are a couple of examples in Missouri that have a lot of protected-only left turn signals: MO 291 in Independence: https://goo.gl/maps/p9MobgTqLBCBPbjx9 , and MO 152 near Liberty: https://goo.gl/maps/aB5s9hEdd5GUQF6k6 .  And for the other end of the left turn philosophy spectrum (if you want to call it that), here are some expressways in New Jersey that keep the signals to two phases as much as possible: NJ 138 east of I-195: https://goo.gl/maps/bcdBczeDoqdhujwS9 , and US 1 and NJ 18 south of New Brunswick: https://goo.gl/maps/npjdFbFRJnHquCuk6 .  (And yes, I recognize the gray area in the definition of "expressway," as some would prefer the term not to include anything with a driveway, which is why I picked ones with fewer driveways rather than many, but I still disagree with the driveway-excluding definition, as I don't believe the term "partial control of access" was ever intended to mean "absolutely no driveways whatsoever.")

(Edited because I typed "left term" when I meant "left turn."  I wonder if that's a first.)

Quote from: jakeroot on April 08, 2021, 02:22:46 PM
Is that an intersection that needs more than two phases? I don't see why. Unless there are insane backups at rush hour.

I would post busier intersections that more clearly warrant more than two phases, but it seems Chicago has been installing a lot more left-turn arrows over the last two decades since I lived in the area.

Quote from: stridentweasel on April 08, 2021, 05:24:17 PM
Jughandles do take up a lot of land, and slip ramps aren't the safest things to cross on foot.  Although, in New Jersey, you'll often find that jughandles tend to be on highways that don't have sidewalks to begin with, but sometimes, yes, they do have to cross a sidewalk.  As for median U-turns, the variety that they use in Michigan typically involve roads with a huge right-of-way, but in those cases, the U-turns don't extend beyond the right-of-way (one might infer that the width was designed to accommodate them).

I don't mean to imply that they are urban disasters by any stretch, but they certainly seem to end up wider than a typical arterial road.

Quote from: stridentweasel on April 08, 2021, 05:24:17 PM
It's worth noting that Tucson has started using downstream U-turns similar to the Michigan left concept, although the ones I know of in Tucson involve loons rather than extra-wide medians.  Examples: https://goo.gl/maps/awya3hGXVpjddaf5A

Yeah, I've been seeing those. I'm indifferent to them.

Quote from: stridentweasel on April 08, 2021, 05:24:17 PM

Quote from: jakeroot on April 08, 2021, 02:20:11 PM
An engineer near me once claimed "the best left turn is a skipped left turn". In other words: default to permissive.

I'm not sure I fully understand the quotation.  "Skipped" as in, the signal has the ability to skip the protected phase?

I think I slightly misquoted it: "the best left turn *phase" is a skipped left turn *phase*". Meaning exactly what you wrote. If you can skip the green arrow, try and do so.

I'm pretty much alone in my thinking, but my favorite controlled left turn is a T-intersection all-way stop when I'm turning from the ending road onto the through road.

Protected-only is a close second, mostly since they take some pressure off me.

Quote from: kphoger on April 08, 2021, 12:47:17 PM
Didn't North Avenue (IL-64) use to have a section or two like this?  I can't seem to find it on GSV right now, but maybe they got rid of that.

* North Avenue at Roy Avenue (https://goo.gl/maps/xmsbp6yf3FMFZins7)

* North Avenue at Cornell Avenue/35th Avenue (https://goo.gl/maps/Los4kmWy6nyVytRR7)

* North Avenue at Hawthorne Avenue (https://goo.gl/maps/kuF6Sb2MwLXMxysc6)

---

Also a couple sections on Palatine Road but with one way frontage roads.

* Palatine Road at Windsor Drive (https://goo.gl/maps/QFb2oekgLsa2heX28)

* Palatine Road at Schoenbeck Road (https://goo.gl/maps/kiHbbMYgYNJktu8K7)

* Palatine Road at Wheeling Road (https://goo.gl/maps/zbQwqVAjxXonFJrr8)

Quote from: 1 on April 08, 2021, 01:34:08 PM

Quote from: webny99 on April 08, 2021, 01:15:31 PM
What are some examples of signals with more than two phases that could be reduced to two? Most that I can think of that have four need all four.

Take MA 114 and MA 133 in North Andover, for example. Very few people should be turning left from 133, both eastbound and westbound, since there's a faster connector (MA 125 on one side, Waverley Rd./High St. on the other). While the lefts are permissive here, if they would have to be upgraded to protected, they should be banned entirely so it can be 3 phases instead of 4.

I would even say ban them now; while it doesn't save a phase, it still reduces crashes.

That's somewhat similar to these three intersections (https://www.google.com/maps/place/Twelve+Corners,+Brighton,+NY+14618/@43.1270218,-77.566649,18z/data=!4m5!3m4!1s0x89d6b55ec4b625bd:0x506f7651c87cff77!8m2!3d43.127007!4d-77.5655546!5m1!1e1) in a triangle in Brighton, NY, known locally as Twelve Corners. The second left turn is banned on all three outside approaches, as shown here (https://www.google.com/maps/@43.127051,-77.5651857,3a,75y,303.96h,73t/data=!3m6!1e1!3m4!1sl8_bZ7QRo4FiErkbwKriMQ!2e0!7i16384!8i8192!5m1!1e1). (It doesn't matter for the three inside approaches, since the nonsensical turn movement is a right turn.)

Monroe/Elmwood is three-phase with arrows on Monroe, Elmwood/Winton is three-phase with arrows on Elmwood, and Winton/Monroe is two-phase. It seems to work fine as-is, but it's also a very specific situation. I can't think of many other examples where arrows could be easily removed, since most intersections don't have such convenient shortcuts.

Quote from: Revive 755 on April 08, 2021, 10:20:28 PM

Quote from: kphoger on April 08, 2021, 12:47:17 PM
Didn't North Avenue (IL-64) use to have a section or two like this?  I can't seem to find it on GSV right now, but maybe they got rid of that.

* North Avenue at Roy Avenue (https://goo.gl/maps/xmsbp6yf3FMFZins7)

* North Avenue at Cornell Avenue/35th Avenue (https://goo.gl/maps/Los4kmWy6nyVytRR7)

* North Avenue at Hawthorne Avenue (https://goo.gl/maps/kuF6Sb2MwLXMxysc6)

---

Also a couple sections on Palatine Road but with one way frontage roads.

* Palatine Road at Windsor Drive (https://goo.gl/maps/QFb2oekgLsa2heX28)

* Palatine Road at Schoenbeck Road (https://goo.gl/maps/kiHbbMYgYNJktu8K7)

* Palatine Road at Wheeling Road (https://goo.gl/maps/zbQwqVAjxXonFJrr8)

Thank you.  The Palatine Road examples are what I was looking for, but it appears left turns at all of your North Avenue examples are now handled in the typical way from the main lanes:  left-turn lane, five-section signal.

Quote from: kphoger on April 09, 2021, 12:00:56 PM

Quote from: Revive 755 on April 08, 2021, 10:20:28 PM

Quote from: kphoger on April 08, 2021, 12:47:17 PM
Didn't North Avenue (IL-64) use to have a section or two like this?  I can't seem to find it on GSV right now, but maybe they got rid of that.

* North Avenue at Roy Avenue (https://goo.gl/maps/xmsbp6yf3FMFZins7)

* North Avenue at Cornell Avenue/35th Avenue (https://goo.gl/maps/Los4kmWy6nyVytRR7)

* North Avenue at Hawthorne Avenue (https://goo.gl/maps/kuF6Sb2MwLXMxysc6)

---

Also a couple sections on Palatine Road but with one way frontage roads.

* Palatine Road at Windsor Drive (https://goo.gl/maps/QFb2oekgLsa2heX28)

* Palatine Road at Schoenbeck Road (https://goo.gl/maps/kiHbbMYgYNJktu8K7)

* Palatine Road at Wheeling Road (https://goo.gl/maps/zbQwqVAjxXonFJrr8)

Thank you.  The Palatine Road examples are what I was looking for, but it appears left turns at all of your North Avenue examples are now handled in the typical way from the main lanes:  left-turn lane, five-section signal.

I am looking through these pictures of Palatine Rd. and I'm not understanding the benefit of allowing left turns from the service road.  Left turns in the service road would require a separate signal phase from thru traffic, thus adding phases to the signal and slowing everyone down.  It would seem easier to use some of the ROW of the service road to make the main road wide enough for left turn lanes. 

Here is another example of left turn from a service road, but it is limited to buses.  The westbound Q46 bus comes from Union Turnpike, makes a right onto the Queens Blvd service road and discharges all its passengers at the first stop.  (This stop is right next to the subway entrance.)  It then picks up a new set of eastbound passengers at the same stop and drives along the service road to this traffic signal.  When main lanes get a protected left, buses also get a left to make a u-turn to head back to Union Turnpike.

https://www.google.com/maps/@40.7160848,-73.833132,3a,37.5y,307.47h,85.92t/data=!3m6!1e1!3m4!1s2UBDSRDeVr3x4kIHUnNHLg!2e0!7i16384!8i8192

I don't want to pointlessly bump a topic, but there is something I wanted to add.  I vaguely remember hearing something along the lines of, one of the reasons jughandles didn't catch on more is because traffic signal technology advanced since the 1950s to produce more efficient intersections.  Obviously, the FYA is a lot newer than jughandles, but this leaves me wondering a few things.  Did protected-only left turns come out before protected/permissive signals?  When were protected/permissive left turns first used (and where)?  And why do so many places still use protected-only left turns when, absent of a rigorous study on my part, it at least looks like protected/permissive would be feasible?

Oklahoma seems to be one place with a lot of protected-only left turns in places that at least appear as if protected/permissive would be feasible.  Just look at US 69 in Muskogee, for example.  FWIW, the city I live in has been moving to protected/permissive about everywhere it can, but stopping short of going full-Tucson with protected/permissive double left turns.

Quote from: mrsman on April 11, 2021, 11:54:28 AM

Quote from: kphoger on April 09, 2021, 12:00:56 PM

Quote from: Revive 755 on April 08, 2021, 10:20:28 PM

Quote from: kphoger on April 08, 2021, 12:47:17 PM
Didn't North Avenue (IL-64) use to have a section or two like this?  I can't seem to find it on GSV right now, but maybe they got rid of that.

* North Avenue at Roy Avenue (https://goo.gl/maps/xmsbp6yf3FMFZins7)

* North Avenue at Cornell Avenue/35th Avenue (https://goo.gl/maps/Los4kmWy6nyVytRR7)

* North Avenue at Hawthorne Avenue (https://goo.gl/maps/kuF6Sb2MwLXMxysc6)

---

Also a couple sections on Palatine Road but with one way frontage roads.

* Palatine Road at Windsor Drive (https://goo.gl/maps/QFb2oekgLsa2heX28)

* Palatine Road at Schoenbeck Road (https://goo.gl/maps/kiHbbMYgYNJktu8K7)

* Palatine Road at Wheeling Road (https://goo.gl/maps/zbQwqVAjxXonFJrr8)

Thank you.  The Palatine Road examples are what I was looking for, but it appears left turns at all of your North Avenue examples are now handled in the typical way from the main lanes:  left-turn lane, five-section signal.

I am looking through these pictures of Palatine Rd. and I'm not understanding the benefit of allowing left turns from the service road.  Left turns in the service road would require a separate signal phase from thru traffic, thus adding phases to the signal and slowing everyone down.  It would seem easier to use some of the ROW of the service road to make the main road wide enough for left turn lanes. 

Here is another example of left turn from a service road, but it is limited to buses.  The westbound Q46 bus comes from Union Turnpike, makes a right onto the Queens Blvd service road and discharges all its passengers at the first stop.  (This stop is right next to the subway entrance.)  It then picks up a new set of eastbound passengers at the same stop and drives along the service road to this traffic signal.  When main lanes get a protected left, buses also get a left to make a u-turn to head back to Union Turnpike.

https://www.google.com/maps/@40.7160848,-73.833132,3a,37.5y,307.47h,85.92t/data=!3m6!1e1!3m4!1s2UBDSRDeVr3x4kIHUnNHLg!2e0!7i16384!8i8192

I'm not personally a fan of Palatine Rd exactly for the reason you stated, and I live about ten minutes away from it, so I'm pretty familiar with the road. The light takes a long time to cycle through, with phases for the Palatine Rd thru-traffic, the side streets which now all have protected-permissive left signals also, and two separate phases for the frontage roads, one for each direction. There's been times where I've hit all three of these lights wrong while on Palatine and it's not fun waiting.

In an ideal world I'd like to see IDOT convert these three intersections to something similar to what's at IL-83 / Elmhurst Rd. Then you'd only have to deal with traffic at Rand Rd, Arlington Heights Rd, and Kennicott Dr.

Maybe this is a niche, but I really like double left permissive left turns. There is one near me with 2 doghouse signals (my favorite type of signal), so that is my favorite intersection.

Quote from: stridentweasel on April 21, 2021, 06:56:33 AM
Oklahoma seems to be one place with a lot of protected-only left turns in places that at least appear as if protected/permissive would be feasible.  Just look at US 69 in Muskogee, for example.  FWIW, the city I live in has been moving to protected/permissive about everywhere it can, but stopping short of going full-Tucson with protected/permissive double left turns.

It very much depends on the city. Damn near every intersection in Norman that isn't a double left is protected/permissive, including some where it's probably not very helpful due to the volume of oncoming traffic.

^ I would think this is something where the State DOT should step in when it's a State or US highway.

Quote from: JoePCool14 on April 22, 2021, 10:03:47 AM

Quote from: mrsman on April 11, 2021, 11:54:28 AM

Quote from: kphoger on April 09, 2021, 12:00:56 PM

Quote from: Revive 755 on April 08, 2021, 10:20:28 PM

Quote from: kphoger on April 08, 2021, 12:47:17 PM
Didn't North Avenue (IL-64) use to have a section or two like this?  I can't seem to find it on GSV right now, but maybe they got rid of that.

* North Avenue at Roy Avenue (https://goo.gl/maps/xmsbp6yf3FMFZins7)

* North Avenue at Cornell Avenue/35th Avenue (https://goo.gl/maps/Los4kmWy6nyVytRR7)

* North Avenue at Hawthorne Avenue (https://goo.gl/maps/kuF6Sb2MwLXMxysc6)

---

Also a couple sections on Palatine Road but with one way frontage roads.

* Palatine Road at Windsor Drive (https://goo.gl/maps/QFb2oekgLsa2heX28)

* Palatine Road at Schoenbeck Road (https://goo.gl/maps/kiHbbMYgYNJktu8K7)

* Palatine Road at Wheeling Road (https://goo.gl/maps/zbQwqVAjxXonFJrr8)

Thank you.  The Palatine Road examples are what I was looking for, but it appears left turns at all of your North Avenue examples are now handled in the typical way from the main lanes:  left-turn lane, five-section signal.

I am looking through these pictures of Palatine Rd. and I'm not understanding the benefit of allowing left turns from the service road.  Left turns in the service road would require a separate signal phase from thru traffic, thus adding phases to the signal and slowing everyone down.  It would seem easier to use some of the ROW of the service road to make the main road wide enough for left turn lanes. 

Here is another example of left turn from a service road, but it is limited to buses.  The westbound Q46 bus comes from Union Turnpike, makes a right onto the Queens Blvd service road and discharges all its passengers at the first stop.  (This stop is right next to the subway entrance.)  It then picks up a new set of eastbound passengers at the same stop and drives along the service road to this traffic signal.  When main lanes get a protected left, buses also get a left to make a u-turn to head back to Union Turnpike.

https://www.google.com/maps/@40.7160848,-73.833132,3a,37.5y,307.47h,85.92t/data=!3m6!1e1!3m4!1s2UBDSRDeVr3x4kIHUnNHLg!2e0!7i16384!8i8192

I'm not personally a fan of Palatine Rd exactly for the reason you stated, and I live about ten minutes away from it, so I'm pretty familiar with the road. The light takes a long time to cycle through, with phases for the Palatine Rd thru-traffic, the side streets which now all have protected-permissive left signals also, and two separate phases for the frontage roads, one for each direction. There's been times where I've hit all three of these lights wrong while on Palatine and it's not fun waiting.

In an ideal world I'd like to see IDOT convert these three intersections to something similar to what's at IL-83 / Elmhurst Rd. Then you'd only have to deal with traffic at Rand Rd, Arlington Heights Rd, and Kennicott Dr.

Sure, a full fledged grade separation is wonderful, but so expensive that only a limited number of surface intersections can be converted as such.

Quote from: stridentweasel on April 21, 2021, 06:56:33 AM
<SNIP> And why do so many places still use protected-only left turns when, absent of a rigorous study on my part, it at least looks like protected/permissive would be feasible?

Oklahoma seems to be one place with a lot of protected-only left turns in places that at least appear as if protected/permissive would be feasible.  Just look at US 69 in Muskogee, for example.  FWIW, the city I live in has been moving to protected/permissive about everywhere it can, but stopping short of going full-Tucson with protected/permissive double left turns.

I think this has to do, in part, with the signal philosophy of the local public works department. Some agencies have very rigid criteria as to when they will consider PPLT phasing as opposed to protected-only, whereas other agencies may be more lax.

It also likely has to do with cost. There just may not be funds available to convert protected-only to PPLT when there's other competing needs vying for limited dollars, especially for smaller jurisdictions. To make this conversion, you have to purchase and install the new signal heads as well as potentially pull new wiring. If the existing signal controller doesn't have PPLT logic or doesn't have the FYA logic (which may be likely if the controller was installed before the mid-2000's), you may need to go through a bigger monetary investment of replacing the controller to implement PPLT phasing. For some agencies, the cost may not be worth it.

Quote from: stridentweasel on April 23, 2021, 07:02:30 AM
^ I would think this is something where the State DOT should step in when it's a State or US highway.

Depends on how things are set up. For example, in Nevada, NDOT may maintain the state highway, but they actually don't maintain the signals they install on said highways–signal operation is generally left to the local city or county jurisdiction. The state may not get a say unless they're going to provide funding to the local agency for any signal upgrades, or some other agreement is brokered.

Quote from: MCRoads on April 22, 2021, 12:10:35 PM
Maybe this is a niche, but I really like double left permissive left turns. There is one near me with 2 doghouse signals (my favorite type of signal), so that is my favorite intersection.

Personal opinion: double doghouses look gross.

Quote from: stridentweasel on April 23, 2021, 07:02:30 AM
^ I would think this is something where the State DOT should step in when it's a State or US highway.

I'm of two minds on this. Having the state DOT assert jurisdiction over state highways means that signal policy is uniform statewide on state highways, which is good, especially on lengths of rural highway where one is passing through several small cities with stoplights where the state highway intersects the main drag.

However, it means that large cities that have state highways passing through them will have corridors where the signals will be consistent with each other, but not with the rest of the city. I'm thinking about MoDOT specifically here, which makes no attempt at making its signals and signal signage resemble nearby city installs in style or operation. This particularly sticks out in cities like Springfield which are criss-crossed by a lot of state highways.

In Oklahoma specifically, I'm kind of glad that ODOT doesn't enforce policy on city-maintained signals, because their signal installations leave a lot to be desired. Many of their installations in McClain County still use incandescent bulbs, and I can think of one that has extremely laggy actuation equipment, so you are left to sit at a red light waiting to turn for a kind of absurd amount of time at 12am.

Quote from: roadfro on April 24, 2021, 01:51:37 PM
There just may not be funds available to convert protected-only to PPLT when there's other competing needs vying for limited dollars, especially for smaller jurisdictions.

Was protected-only invented before PPLT?  Or was protected-only just really over-used for a long period of time, and if so, do you know what drove that philosophy?  Was it simply a matter of being overly cautious?  I can see that, except it seems inconsistent with allowing unprotected left turns at most non-signalized intersections, which tends to happen in most states that are not New Jersey.

Quote from: stridentweasel on April 24, 2021, 10:40:12 PM

Quote from: roadfro on April 24, 2021, 01:51:37 PM
There just may not be funds available to convert protected-only to PPLT when there's other competing needs vying for limited dollars, especially for smaller jurisdictions.

Was protected-only invented before PPLT?  Or was protected-only just really over-used for a long period of time, and if so, do you know what drove that philosophy?  Was it simply a matter of being overly cautious?  I can see that, except it seems inconsistent with allowing unprotected left turns at most non-signalized intersections, which tends to happen in most states that are not New Jersey.

I can't speak with certainty without doing additional research, but it seems reasonable to conclude that protected-only phasing has been around far longer than PPLT phasing (at least through phasing types that use doghouses or FYA displays now in the MUTCD). My hunch is that protected-only phasing was developed as a safety measure (beyond permitted-only) for busy intersections or possibly a capacity measure, and then PPLT displays were later adopted to help reduce delay during non-peak periods.

Protected-only still seems to be overused by some jurisdictions...possibly because of old policy or safety rationales held by the agency ("a permitted left turn across two lanes is unsafe", "a permissive turn when opposing speed limit is 40 or greater causes increased crashes", etc. [neither of which I 100% agree with]), possibly because the agency has not sought to make any changes (operating under the "if it ain't broke..." philosophy or otherwise), or possibly because nobody has ever brought up the idea of using PPLT's.

Quote from: roadfro on April 24, 2021, 01:51:37 PM
It also likely has to do with cost. There just may not be funds available to convert protected-only to PPLT when there's other competing needs vying for limited dollars, especially for smaller jurisdictions. To make this conversion, you have to purchase and install the new signal heads as well as potentially pull new wiring. If the existing signal controller doesn't have PPLT logic or doesn't have the FYA logic (which may be likely if the controller was installed before the mid-2000's), you may need to go through a bigger monetary investment of replacing the controller to implement PPLT phasing. For some agencies, the cost may not be worth it.

I would be curious if the logic on older controllers would permit changing the left turns from protected-only to permissive-only (by removing the left turn signals).

Good example is this intersection in Tacoma (https://goo.gl/maps/TLJnYf2hHijXMTa48). Neither street possesses anywhere near the traffic levels required for a protected-only left turn, much less a PPLT. Assuming the controller logic isn't capable of PPLT (either "yield on green" or FYA), it would be easier to simply rip out the protected lefts altogether.

Quote from: jakeroot on April 25, 2021, 03:23:05 PM

Quote from: roadfro on April 24, 2021, 01:51:37 PM
It also likely has to do with cost. There just may not be funds available to convert protected-only to PPLT when there's other competing needs vying for limited dollars, especially for smaller jurisdictions. To make this conversion, you have to purchase and install the new signal heads as well as potentially pull new wiring. If the existing signal controller doesn't have PPLT logic or doesn't have the FYA logic (which may be likely if the controller was installed before the mid-2000's), you may need to go through a bigger monetary investment of replacing the controller to implement PPLT phasing. For some agencies, the cost may not be worth it.

I would be curious if the logic on older controllers would permit changing the left turns from protected-only to permissive-only (by removing the left turn signals).

Good example is this intersection in Tacoma (https://goo.gl/maps/TLJnYf2hHijXMTa48). Neither street possesses anywhere near the traffic levels required for a protected-only left turn, much less a PPLT. Assuming the controller logic isn't capable of PPLT (either "yield on green" or FYA), it would be easier to simply rip out the protected lefts altogether.

Removing a protected-only phase and having no separate left turn phases shouldn't be a problem for most signal controllers.

The initial transition from doghouses to FYAs may have been a challenge in some cases, because older signal controllers didn't have the programming to run the FYA logic and I believe in some cases couldn't be reprogrammed to do so. (Similarly, many places running Dallas Phasing prior to the proliferation of FYA needed special controller logic to run it, because some of the principles conflict with standard NEMA signal controller programming.)