What's Your Favorite Controlled Left Turn (and Why)?

[Ned Weasel]

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?

[hotdogPi]

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.

[webny99]

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 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.

[kphoger]

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

[Ned Weasel]

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

[hotdogPi]

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 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.

[kphoger]

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, example 2, example 3.

[Ned Weasel]

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, example 2, example 3.

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?

[SkyPesos]

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.

[webny99]

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.

[hotdogPi]

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.

[kphoger]

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 (intersection chosen at random).

[jakeroot]

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.

[jakeroot]

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 (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.

[Ned Weasel]

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).

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

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.)

[kphoger]

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.

[jakeroot]

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.

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.

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.

[interstatefan990]

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.

[Revive 755]

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

* North Avenue at Cornell Avenue/35th Avenue

* North Avenue at Hawthorne Avenue


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

* Palatine Road at Windsor Drive

* Palatine Road at Schoenbeck Road

* Palatine Road at Wheeling Road

[webny99]

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 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. (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.

[kphoger]

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

* North Avenue at Cornell Avenue/35th Avenue

* North Avenue at Hawthorne Avenue


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

* Palatine Road at Windsor Drive

* Palatine Road at Schoenbeck Road

* Palatine Road at Wheeling Road

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.

[mrsman]

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

* North Avenue at Cornell Avenue/35th Avenue

* North Avenue at Hawthorne Avenue


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

* Palatine Road at Windsor Drive

* Palatine Road at Schoenbeck Road

* Palatine Road at Wheeling Road

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

[Ned Weasel]

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.

[JoePCool14]

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

* North Avenue at Cornell Avenue/35th Avenue

* North Avenue at Hawthorne Avenue


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

* Palatine Road at Windsor Drive

* Palatine Road at Schoenbeck Road

* Palatine Road at Wheeling Road

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.

[MCRoads]

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.