Lagging Left Turns Would Improve Crosswalk Safety at Complex Intersections

Useful location for lagging left turn signal
People have already started crossing Halsted on a green light, even though a late left-turning motorist is stuck in the intersection.

When left turn signals are installed, they typically turn green at the start of a street’s green phase. However, simply reversing that order and putting left turns at the end of the green phase could reduce conflicts between turning cars and people walking in the same direction. As left turn signals have been installed at more Chicago intersections, motorists often are caught completing their left turns just as through traffic – and pedestrians – get a green light. The resulting conflict isn’t safe for anyone.

It’s standard engineering practice to have a “leading left turn phase,” in which the green-arrow light for protected left turns goes first, before through traffic gets a green light. However, Chicago drivers often make left turns at the end of the green phase, after opposing traffic has cleared the intersection.

One example of an intersection where the leading left turn poses a problem for pedestrians is across Halsted Street at Grand and Milwaukee Avenues. During the weekday afternoon rush hour, and at peak times on weekends, motorists end up finishing their turns after through traffic has gotten a green — and end up driving into a crowd of pedestrians. This has happened ever since October, when the Chicago Department of Transportation installed a left-turn signal on Grand Avenue.

To eliminate this conflict, the turn signal here could be shifted to a “lagging left turn,” which puts left turns at the end of the phase, instead of at the beginning. Moving the left turn to the end of the Grand green light would allow pedestrians to cross once the light turns green, then allow any drivers waiting to make a left to finish their turns within a protected left-turn cycle.

Useful location for lagging left turn signal
The leading left turn signal cuts short the pedestrian crossing time across Grand, and split left-turning traffic. This photo shows four motorists turning, and thus blocking people from crossing the street during their green phase.

Lagging left turns are highlighted by the Chicago Pedestrian Plan as a “tool for safer streets.” The plan even mentions that, by reducing conflicts between pedestrians and vehicles, the lagging left turn can even improve car traffic “operations,” and can be done inexpensively since it’s merely reprogramming existing infrastructure. However, CDOT will only install lagging lefts where they “will not negatively affect the operations of the intersection” – engineer-speak for slowing down drivers.

The Pedestrian Plan specifically recommends lagging left turns at intersections with any of the following characteristics:

  • A left turn phase with high-pedestrian volumes. At Milwaukee/Grand/Halsted? Yes
  • Three or more crashes in three years between left turn vehicles and pedestrians. This is most likely the case
  • People crossing during the left turn phase. Maybe
  • The intersection gives pedestrians a head start with a leading pedestrian interval. Not at this intersection

CDOT points to a successful lagging left at Huron Street and Fairbanks Court in Streeterville, near Northwestern Memorial Hospital. Previously, drivers were “unable to turn left” because people were walking across during the entire green phase. After installing a lagging left turn, “pedestrians crossed safely with their signal and the issues with vehicles queueing disappeared.”

Based on those qualifications, the Milwaukee/Grand/Halsted intersection seems like a sure bet for a lagging left turn. Where else in Chicago would a lagging left turn improve pedestrian and vehicle safety?

  • Ross

    I’m pretty familliar with this intersection, and a change like that would do wonders. Also would work great on North Ave and Clybourn, where I see drivers getting caught making left turns due to pedestrians ALL the time.

  • A lot of drivers I see making left turns from SB Clybourn onto EB North Avenue make the turn but cannot complete the turn during the green arrow phase because the traffic has backed up from the light at Halsted (and thus block the crosswalk). A lagging left turn would likely not have this problem and you wouldn’t even have to adjust the signal at Halsted.

  • steven crane

    i’m a growing believer in pedestrian scrambles, or at least a brief period of a four-way-red-light for all busy intersections.

    an analogous but not-quite-the-same situation is NB kimball at lawrence for right-turning cars. you can’t make a right turn on red because pedestrians crossing kimball. you can’t make a right turn on green because pedestrians crossing lawrence. the volume of pedestrians is so high that there should be a phase to let them clear the intersection, independent of vehicle traffic.

  • Mcass777

    I agree. Especially at this location where the city has reversed the red/ green light order. Most intersections seem to transfer counter clockwise but here it was reversed last year to clockwise. Many bikers and peds (including me) assume they are next to get the green light and start moving but they still have the red.

  • John

    Lagging lefts can indeed be a good solution at many locations. However, the downside is that you have to install the turn arrows in both directions and have them go at the same time to avoid introducing a left turn trap (think “oncoming traffic has longer green” like at Damen/Elston/Fullerton). Sometimes only one direction needs a left turn arrow. Sometimes one direction needs a longer turn arrow than the other.

    Another thing to consider at complex intersections is banning left turns altogether. When you have a six-legged intersection, there isn’t a lot of spare time to devote to left turn phases. At some interections (I’m thinking Damen/North/Milwaukee), you could potentially take the space from the left turn lanes and use it to widen sidewalks instead.

  • Damen/North/Milwaukee: I’ve been contemplating that, getting rid of all left turns from the intersection. Allowing them doesn’t seem to do anyone any good, except the person wanting to turn left. No buses need to turn left, and turning left means you are turning into 1-2 streets of pedestrians crossing, not just one like at 4-way intersections.

  • FG

    So CDOT has the staff to monitor all the intersections make appropriate plans? I ask because last time I heard staff numbers (admittedly a long time ago) for traffic management staff, Evanston had more than double the number Chicago did in that depeartment. I see this becoming politicized (i.e. citizen and aldermanic requests rather than actual need or inappropriate solutions due to lack of staff).

    Doesn’t LA traffic generally lag on left turns? I’ve heard they do. Local quirks are fun (Michigan’s flashing orange, Seattle’s fear of being caught in an intersection after a light changes, Minneapolis’ passive-aggressive merges, etc).

  • Mishellie

    This would help immensely on Michigan Ave at both Chicago AND Superior (at LEAST.) As soon as the light turns green, peds start walking, but there are cars turning into them.

  • kastigar

    I’ve long advocated for getting rid of ALL left turn signals.

    Think about it: whenever the left turn signal is activated pedestrian traffic must stop in all directions. Pedestrians stop, so cars can move.

    When it’s raining, pedestrians must stand in the rain and wait while motorists inside their cars can drive. When it’s cold, pedestrians must wait in the cold which motorists inside their heated cars can drive though easier. When it’s hot pedestrians must swelter in the sun, while motorists sit inside their air-conditioned cars.

    Balance. Eliminate all left-turn arrows.

  • Buff Bagwell IV

    This is just silly and also increases the risk of a pedestrian (in most of the city who are a rare occurrence FYI) getting hit by a left hand turner.

  • Katja

    A thing not mentioned by this article, but that’s important:

    Right now, if you want to cross Milwaukee, you must cross during the green on Halsted. When it’s getting ready to turn green on Grand, there’s a “don’t walk” sign for Milwaukee, due to the left turn signal. This “don’t walk” across Milwaukee remains on during the green phase on Grand, even though the ostensible reason for not crossing (the left turn arrow) isn’t on anymore. This leads to pedestrians sometimes looking both ways across Milwaukee, then going anyway.

    Having a lagging arrow would give pedestrians significantly more time to cross Milwaukee legally.

  • Katja

    Is there a lagging left arrow at Western/Lawrence? I feel like there is.

    I don’t remember lagging lefts in LA, but haven’t been there in a while. That’s a place that sure knows traffic, it’d be interesting to find whether lagging lefts work better for them.

  • Coolebra

    LA drivers don’t pay attention to red lights, let alone leading/lagging green arrows . . . they rank 188 out of 200 when it comes to cities with the best drivers.

  • rohmen

    Is the resulting couple minute or so reduction in wait time a pedestrian would have before being able to cross a street by eliminating a left-turn arrow worth an increase in the exact type of pedestrian/turning-car conflicts this article notes and seeks to address really worth it?

    Eliminating left turn arrows does not eliminate cars turning left, it likely just means cars would be even more aggressive to crossing pedestrians at intersections where the left signal was removed. Take a walk in the loop and watch how taxis deal with pedestrians in intersections where a left-turn arrow isn’t present for a good example of what I’m talking about.

  • BlueFairlane

    This argument always seems silly to me.

    Consider this example. Say you’re walking a mile-long stretch of road. Just to pick an example, let’s put this stretch on Western Ave., from Fullerton to North. (You can put it anyplace else you’d prefer.) If you walk at a fairly average 3 miles per hour, the walking portion of this stroll not counting stop time will take you 20 minutes.

    If you count the lights both at Fullerton and at North, there are six lights along this stretch. Two of these are associated with the dogleg at Wabansia, so the left turn at one of them won’t affect you. Say you get caught at each of the other five, and each of those five has a left turn sequence. A left turn signal lasts, at most, 15 seconds. So waiting for the left turn sequence at each of the five lights adds a total of 1 minute and fifteen seconds to your 20-minute walk, an increase of 6.25%. If it’s raining, getting where you’re going a minute and fifteen seconds earlier isn’t going to keep you dry.

  • cjlane

    There is an existing lagging turn signal at Fullerton and Clybourn. Has *nothing* to do with pedestrian safety, of course, just about clearing the triangle slightly more safely.

  • JasonMath

    There’s a lagging left turn northbound on Western at Van Buren (onto I-290), at least when I was over there two years ago. It has more to do with clearing the turning lane of traffic than pedestrian safety.

  • nikhil trivedi

    There is, and as a driver I love it. Makes turning left so much easier.

  • nikhil trivedi

    Logan and Western would be a great candidate for a lagged-left. I don’t think they expected pedestrians to be there at all when they designed that intersection!

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