Pages Navigation Menu

Have You Examined Your Zipper Lately?



Quick pop-quiz: which of the following is the safer, faster and most efficient way for cars to merge into a single lane of traffic? Is it:

  1. Cars in the lane that’s diminishing should wait to merge until the lane they are driving in is no longer available
  2. Cars in both lanes should slow down, and cars in the diminishing lane should merge into the open lane as soon as possible – cooperation is key!
  3. Cars in the diminishing lane should stop and wait for an opening or a signal that it’s OK to merge into the open lane – courtesy is key!

Think you know the answer?

OK, we admit we might have led you astray by our wording in the choices. The correct answer is actually A, and it’s called the zipper method. But please don’t take that to mean that cooperation and courtesy aren’t required.

When drivers are in a lane that’s about to end or they approach a construction barrier or a road closure, their first instinct may be to merge quickly into the open lane. It sounds logical, and it certainly seems more courteous. But research shows that doing so has two negative outcomes:

First, it unnecessarily crowds a single lane when two lanes of traffic could handle twice the number of cars. Yes, you’ll eventually have to merge, but merging too soon wastes available space on the road while forcing a single line of traffic to grow, backing up traffic farther than necessary. (Flaw #2.)

Cars in the available lane are forced to stop as people try to crowd in, which increases your time in traffic. It also ups the odds of an accident and leaves you feeling bitter when someone doesn’t wait their turn to merge.

Instead, drivers in the diminishing lane should stay in their own lane until they’re just a few yards from the end of their lane. That’s when they should safely merge, and you should let them in, creating a zipper effect.

If you’re feeling skeptical, so were we. But this method has been proven to keep traffic flowing more efficiently. A study conducted by the Texas A&M Transportation Institute found that it reduces backups by up to 50 percent, allowing more cars to get through per hour.

But everyone has to cooperate to make it work. If someone refuses to let a driver merge, the whole system breaks down, and you just spilled your coffee because someone in front of you slammed on their brakes.

So please do your part to keep traffic moving. We’ll all be a little bit happier when we get their sooner. Watch and share this video with people you know.