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Embrace the zipper merge! Resistance is futile.

Embrace the zipper merge… against your human instincts. This spring, Canadian road construction sites have been springing up in the thousands, as they usually do. And on your impeded commute, you can expect to find standard, orange signs warning you that one of two lanes will disappear. If the left lane is closing ahead, instinctively, 90%* of us will move over into the right lane – as a Canadian, I call it the polite lane. Meanwhile, the seemingly impatient continue to roar past us on the left only to “cut in” once the left lane is finally blocked off.

As they do, at minimum, they get some venomous looks. Some drivers may honk, or even try to prevent them from merging which, even if righteously motivated, is patently dangerous. But, there is a chance that the indignation of polite-laners is misguided. Whether the drivers in the fast lane realise it or not, they are pioneers of the “zipper merge,” a technique purported to ease traffic congestion. And science seems to be on their side.

What is the zipper merge?

Well, what is a zipper? Two strips of teeth that interlock to form a single entity. The zipper merge is a similar concept. When drivers see a sign indicating one lane of traffic is about to close, they must continue to use both lanes. This keeps traffic moving smoothly. At the point where the two lanes converge into one, vehicles must alternate into the remaining lane, like a zipper. The practice has been tested many times across the United States with moderate success, and it’s even supported in Saskatoon. That’s all great. But does it actually solve traffic congestion?

Does it work?

According to the experts, the zipper merge can reduce traffic congestion by up to 40%. Even if we halve that estimate, accounting for a highly inefficient deployment of the zipper merge, the benefit would still be tremendous. According to common sense, it will decrease the likelihood that traffic congestion reaches back to affect other points of intersection. The best way to get a sense of how it will work is to see it in action. Here’s footage of the zipper merge in action compared to the traditional approach.

Will it work?

The zipper merge won’t work if its implementation is contingent upon the good grace and self-enlightenment of Saskatchewan’s drivers. Whether I use the entire length of the closing lane out of selfishness or road savvy, most drivers will assume the latter. The result will be dangerous merges into hostile traffic, increasing the risk of collisions. For the zipper merge to work, nearly all drivers need to understand the benefit. They should also understand the easiest way to achieve that benefit.
The concept could be introduced in driver education, but the seeds of that labour would take years to bear fruit. Instead, drivers need simple road signs that suggest things like “Use both lanes until merge point” and “Take turns. Merge here.” This idea has been introduced, with great success, in many North American cities. While Regina has less traffic congestion than many of those cities, it also has a relatively high amount of construction. Therefore, introducing the zipper merge could be a worthwhile investment in the safety (and mental well being) of the city’s drivers.

* A made-up figure.