What's the best way to merge? It's probably not what you think

Jet Sanchez
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Drivers who wait until the last minute to merge when losing a lane may frustrate you, but studies show they are merging correctly.

The zipper merge is a safer and more efficient way to merge in slow-moving, congested traffic. Here is how—and why—it works.

What is the zipper merge?

Zipper merge

The zipper merge, a surprisingly efficient traffic manoeuvre, may initially seem counterintuitive to many drivers.

Named after the interlocking teeth of a zip fastener, this method orchestrates vehicles from two or more lanes to merge seamlessly, akin to the smooth operation of a zip.

In practice, this means that when you're driving on a busy highway and encounter a construction zone sign indicating your lane will soon end, the zipper merge instructs you to remain in your lane until the very end.

At the merge point, vehicles from the terminating lane take turns merging into the continuing lane, ensuring a smooth and orderly transition.

Why does the zipper merge work?

Many drivers, believing they are being courteous, tend to merge as soon as they see the warning sign, often resulting in slower traffic flow and increased congestion.

However, the zipper merge is designed to maximise road space usage, keeping traffic moving more efficiently. By staying in your lane until the merge point and then taking turns with drivers in the adjacent lane, you contribute to a smoother traffic flow.

This method requires cooperation among drivers, who must work together and adhere to the turn-taking principle. It’s crucial to maintain a consistent speed without rushing ahead only to brake abruptly, which can disrupt the flow and cause further delays.

Benefits of the zipper merge

Research has shown that the zipper merge can significantly reduce the length of traffic backups in construction zones.

By promoting similar travel speeds between merging lanes, it enhances safety and reduces the likelihood of accidents.

Additionally, this method helps create a sense of fairness, as all lanes move at a comparable pace, reducing the frustration often associated with merging.

Several countries have adopted the zipper merge, incorporating it into traffic regulations over the past decade.

Studies indicate that this method not only improves traffic flow but also fosters a more equitable driving environment, where the perception of 'cutting in line' is mitigated.

When to avoid the zipper merge

While the zipper merge is highly effective in congested, slow-moving traffic, it is not always the best approach.

In situations where traffic is moving at posted speeds and there are no significant backups, merging earlier into the continuing lane is advisable. This helps maintain the smooth flow of traffic without unnecessary delays.

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