Missouri39s Department of Transportation produced a video with adults walking in cardboard vehicles educating children about the benefits of the zipper merge MODOT
<p>Missouri&#39;s Department of Transportation produced a video with adults walking in cardboard vehicles educating children about the benefits of the zipper merge.</p>

The magic and mystery of the Zipper Merge

The Zipper Merge.

Truck drivers know it works. Traffic engineers know it works. The proof is rock solid.

Why don't motorists get it?

The answer is psychological, visceral and more complicated than most of us imagine, according to those who study traffic from the driver's point of mind. As traffic congestion grows  and road construction makes it worse, states are fighting human nature and ingrained driver habits to persuade motorists to merge the zipper way.

Several states including Minnesota, Missouri, Kansas and Washington are going full speed ahead this summer on public outreach programs to convince motorists that the zipper merge is fair, safe, cuts congestion and can reduce backups by as much as 40 percent. Some states have produced videos showing how to merge. Missouri's Department of Transportation even produced a video with adults walking in cardboard vehicles educating children about the benefits of the zipper merge. Minnesota has an entire website devoted to the maneuver's benefits. Kansas, for instance, uses animated talking barricades to get the point across in its video. Many states are using road signs to tout the benefits of the zipper merge at lane merging spots, and several newspapers have made zipper merges the subject of editorials hoping to sway public sentiment about something that's right but feels so wrong.

The zipper merge gets its name from how the movement looks. In a construction zone for example, drivers are ordered by signs to merge into one lane. The most efficient way is for drivers to fill the two lanes and not stop and merge before the two lanes become one. This holds up traffic (and may be illegal, subject to a fine). When the lanes become one, drivers take turns merging at the end – like a closing zipper.

Unfortunately, most drivers are reluctant to do it and may look down upon drivers who do, according to Dwight Hennessy, PhD., professor of psychology at Buffalo State, who has studied driver psychology for more than 20 years. "In order for zipper to work, we all have to follow the rules. That's really the only thing that makes it work, but there are so many things working against it."

He adds: "When a person drives down the merging lane, we assume they are a jerk, that they're getting away with something because they're moving ahead of us. Now, because they are a jerk, and they're breaking the rules, we are not obligated to let them in. We start getting defensive. On top of that, we think, 'I've already been driving down this lane, and how many other people have gotten in before me?' In our mind the rule is: the law abiding, good, polite citizen gets in the main lane and it's only the jerk who drives in the disappearing lane. We make these judgments about them, that they are terrible people, and we just don't want to let them in. We protect that space. We are very territorial when we drive."

It can get even worse, in drivers' minds, says Hennessy, when motorists believe they are being punished for what they think is the polite action. "'I got over earlier. Why didn't that jackass get over earlier, too?' It creates anger when we think that other people are ripping us off, that they're breaking the rules and they're getting ahead. 'I followed the rules; you didn't, and you're beating me.' This really ticks people off." And, at the merging point the compliant driver, the one who really is driving the best way by doing the zipper merge, has to endure dirty looks from those who feel cheated by the latecomer.

Hennessy says it's worse for truckers who try to do the right thing. "I feel for truck drivers… One of those things that prevents people from zippering is the idea that they don't want  to get stuck at the very end, and I'm certain trucks really don't like getting stuck in the end [because of their length compared to cars]. A lot of people don't like to let trucks in because even though it takes only a couple of seconds longer, our concept of time is so [skewed] when we drive. 'I can't let that truck in because I'm going to be two seconds later getting to work.'"

Like some other proven scientific ideas, many people will simply not believe that the zipper merge works no matter how much evidence is thrown their way, says Hennessy. "States are trying to tell people that you only have to merge one time in the zipper, but people don't necessarily believe it. Even when you present them with real evidence, once they've made up their mind it's over. It's something called belief perseverance. Once we spend our time and energy creating ideas in our minds – even when we are confronted with contrary facts – we still hold onto our ideas."

What will change peoples' minds about the excellence of the zipper merge? Says Hennessy: "How do you change a person's mind who has convinced themselves that is not going to work? This may take time because what we're trying to do, essentially, is change the mind-frame of what the rules are to this game. The more people work at it, the more people who are saying that it works, and the more people who are doing it – even if other people don't like it – and then seeing that it works, then maybe you can change the culture."

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