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Thursday, Aug. 21, 2014 12:01 am

Merge, right?

Too many Illinoisans don’t know how to behave on the road

 There is no traffic situation so bad that drivers can’t make it worse, as I was reminded while driving on I-55 recently. Work on the Des Plaines River bridge required rerouting traffic onto one lane in each direction, resulting in the mother of all merge bottlenecks. Took 40 minutes to get through.

It didn’t need to take quite that long. Most drivers moved out of the affected lane as soon as they saw it was blocked. Only a few drivers continued to drive down the blocked lane, delaying merging until they reached the obstruction. By doing so they risked the wrath of their compatriots of the road. Such behavior is widely damned as queue-jumping, which offends some drivers so much that they pull their cars part-way out of their lane to block the offenders from passing them. (That’ll get you a ticket for improper lane usage, by the way.)  

Drivers who patiently get in line at bottlenecks like this one console themselves with the fact that they are doing the right thing. But an interstate highway is not a movie line. The point of most traffic laws is to keep traffic moving, and the most efficient way to do that is for drivers in both lanes to proceed to the point of obstruction using both lanes, cars in each lane then merging alternately. The maneuver is known as a zipper merge because the cars mesh like teeth on a zipper. Both the feds and state traffic departments have studied the problem extensively, and all came to the same conclusion: The zipper merge speeds up traffic flow by as much as 15 percent and reduces the total length of a backup by 40 percent.  

The problem is, few of the drivers that day were traffic engineers. It wouldn’t help even if a lot of them were; every driver needs to know how it works for zipper merging to work well. In Europe, where drivers are much better informed about how to handle road situations like this, such merges can be done safely and quickly. Here? I read that IDOT put up a sign that read, “Use both lanes, take turns at merge” but I didn’t see it, and it wouldn’t have mattered much if anyone else did. Those who merge early bask in virtue, those who merge later exult in having beaten the game, but everybody is late getting to where they’re going, at a price not only of time but confusion, anxiety and anger.

Merges at speed pose similar problems. I know people who avoid driving on interstates (especially their big-cousins, expressways) because they fear getting onto one. Professional truckers will tell you that merges into traffic are the most dangerous moments in their day. That’s because of the many people who believe – again applying everyday manners to the road – that traffic already on the road should make way for the drivers entering it, as they might expect a stranger to scoot over a few inches to make room under an awning during a sudden rain shower.

Here the problem is not lost time but risks to safety. In California, where I lived for a while, the official driver handbook makes it clear what to do: “Freeway traffic has the right-of-way.” In Michigan the rule is, “Merging motorists shall yield the right-of-way to existing traffic and adjust their speed accordingly.” And Illinois? The Rules of the Road booklet (p. 65) states, “Be ready to either change lanes or allow other traffic to merge into your lane . . . . The driver on the expressway slows down to let the driver on the ramp merge.”  (The Illinois statute book phrases it thus: “The driver of each vehicle on the converging roadways is required to adjust his vehicular speed and lateral position so as to avoid a collision with another vehicle.”)

This is not helpful. Changing lanes to allow other traffic to merge into your lane can’t always be done safely. The whole point of the on-ramp is to enable entering vehicles to reach highway speed so that no one has to slow down; nor can one safely slow down very much when the guy behind you is doing 75 and the entering vehicle is doddering along at 40. That leads to situations that gives liability lawyers wet dreams.

No game can be played well by people who don’t agree on the rules. (Just look at Congress.) We will talk some other time about state drivers’ tests that focus only on what the law requires and not enough on what good driving requires, if indeed better tests are the best way to school the public in a shared road etiquette. If they are not, you have until Sept. 1 to work it out amongst yourselves. That’s when lane restrictions will be imposed on I-55 at Mile 102 north of town for two months. Let me know how you do.

Contact James Krohe Jr. at


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Friday Sept. 20th