Driving has its frustrating moments, but few experiences can make drivers pull out their hair like a stretch of road where two lanes of traffic reduce to one. Some people, not wanting to be rude, move into the proper lane as soon as they see a lane ending sign. Others stay until the last possible moment, only merging when required.

What should you actually do in these situations? Consider the zipper merge.

How to do the zipper merge

The zipper merge (also sometimes called late lane merging) is a pretty simple concept. Picture the cars in two lanes as teeth on each side of an open zipper. As you zip, those teeth take turns slotting above and behind one another as they come together in a single line.

That’s exactly how it can work on a road. As the two lanes of traffic approach the merge point, drivers take turns moving into the oncoming single lane. Right lane, left lane, right lane, left lane.

Those motorists who wait until the last second to get over? They may actually be doing things the most efficient way.

Why zipper merging works

The York Daily Record points out the law doesn’t require the zipper merge. You won’t get in trouble for choosing to move over early, but officials encourage zipper merging because, to put it simply, it works.

Studies have shown it cuts traffic lines significantly, as cars use up more of the road rather than lining up in a single lane. In addition, traffic doesn’t really have to slow down – no slamming on brakes when someone veers over at the last possible moment. Instead, each vehicle would slot in behind and in front of one another, able to just about maintain their normal speed.

Drivers have to cooperate, however, which is where things get tricky. If one motorist decides to not let a fellow driver in, it can slow everyone else down as they adjust. That can lead to anger, some choice words uttered in the privacy of the car and even unpredictable, aggressive driving. That’s not a safe situation for anyone on the road.

Next time you come to a lane closure, remember: It’s OK for motorists to wait to merge.