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How the zipper merge can help beat bottlenecks—and be the polite thing to do

We’ve all been there. A sign warns of a lane closure ahead and you’re faced with two options: immediately merge into the bottleneck and secure your spot in line, or drive to the end of the closing lane before making your move—in front of drivers who waited their turn.

As it’s put in the AMA Insider, there are two driver types—the “line-uppers” and the “late-mergers”—and each tends to be equally convinced their way is best. The former because their behaviour seems polite and less stressful; the latter because their strategy leverages empty road real estate and saves time. But who’s right?

For years, the question has been up there with pineapple on pizza and the series finale of Game of Thrones in its ability to spark debate—especially during BC’s busy construction season. A possible answer is the “zipper merge”.




How does it work?

When there’s a bottleneck, drivers use both lanes fully and proceed to the point of closure (or defined merge area), filling both lanes of traffic rather than merging early to line up in a single lane. That means every car in the lane that's ending can remain in that lane.

At the source of the merge, drivers then alternate, like the teeth on a zipper, into the open lane so that no line of traffic is held up. This technique maximizes available road space, which results in less time spent in line. In fact, research shows it can reduce congestion by as much as 40% (Wow!). And with both lanes filled, no one can zoom past which, let’s admit, is what makes many drivers feel annoyed and cheated.




So why do some drivers zipper merge and others don’t?

The challenge is that as Canadians, our natural instinct to form one lineup and wait for our turn is baked in pretty deep. To many of us, it seems unfair and pushy to rush to the front of any line and overtake anyone who’s been waiting. So, drivers in the closing lane who are practicing the zipper merge properly, mistakenly appear to be merging late and are seen to be cheaters.

While this can hold true in many lineup situations like those at retail or grocery stores or the bank (oh the havoc that would create!), it’s not the case when it comes to zipper merging in traffic. The system is meant to use all the available road space for as long as possible which helps to ensure both lanes are filled and end up moving at an equal pace.

As with any well-intentioned system, all drivers need to be on the same page when it comes to zipper merging. The system won't work if drivers who remain in the closing lane are shunned, as no one will dare do the very thing that makes the zipper merge efficient.


Zipper merge and traffic congestion in BC

In various parts of BC there are “Merge like a zipper” signs in place, such as along Highway 91 within the Lower Mainland. The BC Ministry of Transportation and Infrastructure also provides details on how to properly zipper merge.

A CAA study, “Grinding to a Halt, Evaluating Canada’s Worst Bottlenecks”, concluded that bottlenecks are the single biggest contributor to road delays. The study showed that Canada’s worst bottlenecks are as serious as those in major US cities such as New York and Los Angeles. In Vancouver, the four identified bottlenecks listed below cost drivers half a million hours in lost time due to delays and $13 million in lost productivity each year. It also results in an additional four thousand tonnes of carbon dioxide emissions, which is approximately the same weight as two thousand cars!

  1. Granville Street at SW Marine Drive
  2. West Georgia Street between Seymour Street and West Pender Street
  3. Broadway Street and West 16th Avenue
  4. George Massey Tunnel on Highway 99

So, maybe it’s time to change our views on the zipper merge and those so called “cheaters”? While it’s difficult to get past our philosophies around line ups, there are cases when two lines are better than one.

As the debate around zipper merge continues, one way for all of us to help take the edge off when congestion happens is to maintain driver courtesy and share the road. Acknowledge whenever someone lets you through even if it’s your right of way—a friendly held up hand and head nod can go a long way in keeping everyone relaxed. In the end, each of us has somewhere to go and we all want to get there safely—and still in a great mood.




Tips for a safe and successful zipper merge (when conditions allow):

The zipper merge works best in traditional congestion situations like construction zones. If a lane closure is due to a crash or vehicle breakdown, follow the Slow Down Move Over law when you see orange cones, or any vehicle stopped alongside the road that has flashing red, blue or yellow lights to keep emergency workers and/or tow truck operators safe.


Driving in the closing lane

  • Drive consistently. Don’t rush ahead, only to slam on your brakes later.
  • When getting close to the source of the merge, signal your intent which gives other drivers time to notice and react. Then merge in an alternating fashion.
  • If there’s no bottleneck and traffic is moving, feel free to make an early merge if it makes sense.

Driving in the open lane

  • Leave extra room between you and the car ahead and drive consistently.
  • At the source of the merge, give enough room for the car from the closing lane to merge into your lane in an alternating manner.

Practice driver courtesy

  • When driving in a Cone Zone, slow down safely, pay attention to the placement of the cones and watch for roadside workers or sudden traffic changes.
  • Always give other drivers enough space.
  • Avoid aggressive driving behaviours such as tailgating, weaving in and out of traffic, abrupt braking and jack-rabbit starts.

Photo credits: Getty Images

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