Heavy Traffic: The Great Merge Debate

A quick true/false quiz:
- Late merges at lane closings are rude and make traffic worse.
- Variable speed limits only confuse drivers.
- EZ Pass-style automated pay lanes cut down on accidents near tollbooths.
- The nearer you are to a major city, the deadlier the highways.

All false, as you may have guessed.

Technology marches on, but traffic still crawls. Moreover, our knowledge of what makes traffic stop and go inches forward at roughly the same rate. According to a study by the Texas Transportation Institute, total traffic delays in the U.S. increased by 655 percent in the nation’s 26 largest urban areas from 1982 to 2003. It turns out that a new generation of traffic analysts, more computer geek than slide-rule engineer, have demonstrated rather convincingly that everything we know about how to make traffic flow smoothly and efficiently is dead wrong.

More highways don’t help. Fewer highways don’t help. More bike lanes don’t help. No bike lane at all doesn’t help. Raising the speed limit doesn’t help. And neither does lowering it.

What, for the love of what’s left of our lives, can the nation’s engineers, in this, the year 2009, do about traffic? Or are we destined to average two or three hours a day immersed in it, fighting road rage, letting our attention drift, or alternately steaming or shouting behind the wheel, traveling at 10 miles per hour on the world’s finest interstate highway system?

Start with the late merge:

The concept of delaying a merge when two lanes are funneled into one, as often happens during road repair work, caught on with traffic engineers after studies showed that traffic flow speeded up as much 15 percent over the old “merge early and politely” philosophy. The driver you shake your fist at while he speeds by in the lane to be closed is actually making your trip shorter. What happens is that all that early merging creates an underused lane — everybody crammed into one lane while there are still two useable ones. Merging when necessary, in zipper fashion, is the better way to go.

Article Author: Dirk Hanson

Dirk Hanson is a freelance science reporter and novelist who lives in Minnesota. He has worked as a business and technology reporter for numerous magazines and trade publications, and is the author of "The Chemical Carousel: What Science Tells Us About Treating Addiction."
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