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ADOT tests ‘zipper merge’ in Buckeye

ADOT tests ‘zipper merge’ in Buckeye construction zone


zipper merge in Buckeye

ADOT tests ‘zipper merge’ in Buckeye construction zone

An Arizona Department of Transportation (ADOT) project in the West Valley has been using a “zipper merge” to reduce delays when narrowing traffic to one lane.

The merge has been used during daytime hours on westbound Interstate 10 in Buckeye.

A zipper merge works best for construction projects in areas of heavy traffic and slow speeds. Digital signs remind drivers to stay in both lanes until just before the lane restriction occurs. Then, drivers take turns merging from each lane, much like the way the teeth on a zipper close a zipper.

To be effective, drivers approaching such work zones must let go of the idea of merging early.

For safety and efficiency, they also must resist the urge to straddle both lanes.

Studies by the Texas Transportation Institute, Minnesota Department of Transportation and Federal Highway Administration have shown that the zipper merge (thus named because both lanes are used and drivers take turns merging one car at a time, like the teeth of a zipper) improves traffic flow by as much as 15 percent, according to the Detroit News. MnDOT also found it reduces the total length of a backup by as much as 50 percent, and commonly by 40 percent.

A zipper merge can reduce traffic backups by 40 percent, according to the Federal Highway Administration. It also makes driver behavior more predictable — and enhances safety.

ADOT has used the zipper merge concept twice now and will evaluate results to see which future projects may benefit from its implementation.


“Although motorists seem to believe that a single lane of traffic flowing into a work zone should flow through unrestricted and much faster without a slow down for merging traffic, this just does not happen in the real world of traffic hazards,” MnDOT says. “Motorists slow down because of the uncertainty of the drivers’ actions ahead, poor visibility beyond, signs/drums/barricades and (other obstructions). That slows down the rest of the line of traffic, and the longer the queue, the more it slows down and a longer time before it regains speed.”

Can the zipper merge in Buckeye construction zones overcome such deeply rooted aversion? Proponents believe with enough public education and practice, motorists will get the idea. In the meantime — as always — it seems all we can do is stay alert, pay attention to signs, be courteous to other drivers and exercise caution when changing lanes.


Organizations in this Story

Arizona Department of Transportation

206 S 17th Ave
Phoenix, AZ 85007