Is the ‘Michigan Left’ Right for America?
Left turns at intersections are the bane of traffic. They impede traffic flow (a “protected” green arrow holds up the majority of the intersection for a minority of drivers), UPS drivers’ routes are programmed to avoid them, and they’re dangerous for drivers (who often have trouble judging the speed of oncoming drivers, or have their view obstructed in determining whether it’s safe to cross) — not to mention pedestrians, who typically have the “Walk” signal when cars have a left-turn signal (and, because of the aforementioned problems, cars may only be paying attention to pedestrians at the very last moment).
Yesterday, John J. Miller asked me about a regional specialty in the world of traffic, the so-called “Michigan left.” Having spent some time in the environs of the Motor City, I had a passing familiarity with the system, but had sort of filed it away in my brain — and didn’t bring it up in the book. But he raised a very good point: Why isn’t it used elsewhere?
The Michigan left (not to be confused with the “Pittsburgh left”), or the “median U-turn crossover,” is what the Federal Highway Administration, in engineering logo, would call an “alternative intersection treatment.” It originated a few decades ago in response to rising traffic volumes, particularly on suburban arterials. Basically, it seeks to remove that dangerous, traffic-slowing left-turn from the main intersection by having drivers who wish to turn left as they approach an intersection first make a right turn, drive a short ways, then make a u-turn via a short bay, and then head in their desired direction, back through the original intersection.
It looks a little something like this (illustration courtesy of Michiganhighways.org):
If you’re still confused, there’s a nice Flash animation by the Michigan DOT here. MDOT goes on to say that the treatments provide “20 to 50 percent greater capacity than direct left-turns” and, on roads with Michigan lefts, crashes have been reduced “30 to 60 percent overall.”
The only problems I can see with the Michigan left is 1.) You need adequate space for dividing medians (which have a further benefit in reducing head-on crashes) and 2.) Drivers tend to find them a bit confusing and counterintuitive — why should I have to turn right to turn left?
The FHWA also opines that they should only be used in places where left-turning traffic is a relative minority of traffic: “Locations with high left-turning volumes may not be good candidates because the out-of-direction travel incurred and the potential for queue spill back at the median U-turn location could outweigh the benefits associated with removing left-turns from the main intersection.”
The Michigan left is not limited to Michigan. North Carolina has been giving them a spin, while New Jersey-ians of course have the related “Jersey Jughandle.” (I’ll save its intricacies for another post). Then there’s CFIs (ditto). The strangest approach to the left-turn, over-saturated intersection problem I’ve seen recently was on the approach to Sanibel Island, Fla., from Fort Myers, at the intersection of Summerlin and San Carlos: A huge, ghastly, looming “flyover,” which seemed horribly out of place amidst the flat sprawl (a few businesses have been literally lost in its shadows).
But, from what I can tell, the “Michigan left” essentially remains a regional specialty, the traffic equivalent of the state’s sour cherries. What do you say, America, are you ready for the Michigan left at an intersection near you?
ADDENDUM: The reader in the comments below rightfully asked about roundabouts, which are of course superior in both safety and flow to conventional signalized intersections — up to a certain traffic flow (after which they lose effectiveness) and when space permits. I should have qualified the whole discussion by positing Michigan lefts as a superior alternative to “conventional signalized intersections.”
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This entry was posted on Wednesday, July 9th, 2008 at 2:20 pm and is filed under Drivers, Traffic Culture, Traffic Engineering, Traffic Wonkery. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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July 9th, 2008 at 2:29 pm
What’s the typical capacity for multi-lane roundabouts? Thankfully (finally!), a few single- and multi-lane roundabouts have been popping up in the Twin Cities area (Edina has a series of three single-lane roundabouts just south of Southdale and the new SuperTarget in Richfield by the airport is accessed via a multi-lane roundabout). The “Michigan left” just seems like a clumsy approach at a roundabout. I would guess that roundabouts are safer than Michigan lefts?
July 9th, 2008 at 8:38 pm
I have been to Vegas and sat in those “3 lanes turn left” intersections for what seems like 5 to 7 minutes for the signal to turn, thinking a Michigan crossover style boulevard would be superior to those intersections with left turn signals. M-59 in Macomb County handles traffic loads that I think would be impossible without crossover type intersections. They installed a roundabout on M-53 where it branches off to Mound Road and old Van Dyke and I still see people who can’t function in the roundabout because in Michigan ‘crossing solid white lines just because I can’ seems to be the prevailing through, even though you’re in a lane that only goes straight and the sign says you go straight, you want to go left to Mound crossing two other lanes that also go straight through the loop. It’s insane.
And when we had that big power failure in 2003 the divided highways functioned perfectly, the police blocked through traffic making everyone use the crossovers to go straight. Worked like a champ.
-Ron
July 15th, 2008 at 8:00 am
Why isn’t it used elsewhere?
Don’t forget the informal “Michigan Left”.. the old turn right and u-turn. Common in Los Angeles, particularly when traffic is too fast or persistent to cross in one go.
July 18th, 2008 at 10:17 am
I seem to recall that there are a few intersections in New Orleans that work like this. The Melbourne hook turn is related to this idea, too.
July 28th, 2008 at 11:40 am
What is especially annoying and confusing about the MI Left is how they are indicated. Most of the intersections have no graphic sign as shown above in this post. Most tell you what you cannot do: No Left Turn! (But that’s what I have to do.) The indications are almost all counter intuitive to what the driver actually wants to do.
July 29th, 2008 at 6:30 pm
I was taught in California traffic school that you when you turn right, you MUST turn into the nearest lane. (Same when you turn left from/to one-way streets.) Only after entering that lane can you do a lane change to the left.
But the flash demo clearly shows the “North to West” cars turning right into the far lane rather than the near one…. Same when the “East to North” cars cross two lanes at the Stop sign in order to turn right.
So is turning right into a far lane legal in Michigan?
I think the median U-Turn (what you call the “Pittsburgh left”) is a LOT more intuitive.
July 29th, 2008 at 6:31 pm
Heck, even a right-hand cloverleaf makes more sense!
August 3rd, 2008 at 11:00 pm
I live in the city, where most left turns are illegal. So what do we do? We pass the street and go around the block to the right.
Two wrongs don’t make a right, but three right’s do make a left!