After multiple crashes in a U.S. 50 construction zone near the Montrose Regional Airport, the Colorado State Patrol is reminding motorists to use the “zipper merge” to ease congestion and improve safety.

The “zipper” technique, used widely in other states, keeps traffic moving smoothly and shortens backups when drivers merge late and take turns entering a single open lane. The Colorado State Patrol recommends that vehicles fill both lanes as they approach the merge point and then alternate vehicles merging into one lane.

“Drivers already in the open travel lane should avoid blocking the merge lane and welcome drivers to go to the end before alternating with vehicles to enter,” said Col. Mathew Packard, chief of the Colorado State Patrol in a release. “They aren’t acting aggressive — those drivers are actually doing it right and helping to reduce the backup if they wait until the end.”

Cooperation by drivers in alternating merging vehicles with through traffic is essential to successfully improving traffic flow through construction zones, but gaining that cooperation also relies on good signage by the Colorado Department of Transportation reminding drivers of the practice to reduce conflicts due to habitual behavior.

In a Federal Highway Administration study researchers noted that education is vital. A 2021 federal research study supports Packard’s point.

“Public education is vital, since many drivers either do not understand zipper merge or are averse to changing from the long-held practice of early merging,” said the study.

A Federal Highway Administration study conducted in the early 2000s by Pennsylvania, Michigan, and Maryland DOTs with FHWA participation found that well-signed late-merge zones “reduce aggressive driving behavior and smooth overall flow” when traffic volume nears capacity.

A Minnesota Department of Transportation analysis cited by AAA showed the zipper merge can cut traffic backups by up to 40% and decrease road rage by clarifying right-of-way expectations.

A 2024 Iowa State University report found that when signs instructed drivers to merge late, compliance and throughput improved during heavy congestion. The report also noted that “driver understanding and trust in signage are critical to sustained success.”

A Federal Highway Administration 2020 report agreed, stating that properly managed late merges “increase operational efficiency under high-volume conditions.”

CDOT officials say using both lanes until the merge point helps reduce congestion in construction zones and protects roadside workers. Drivers are encouraged to watch for posted signs and to merge late and courteously — one car at a time.

More information about safe zipper merging is available at the Colorado Department of Transportation..