The Virginia Department of Transportation Staunton District is launching a pilot program about zipper merges in work zones.
With a zipper merge, traffic entering an active work zone uses both travel lanes up to the single lane closure and then takes turns operating like two sides of a zipper at the merge point to form a single lane, traveling past the work zone.
For the pilot project, the zipper merge will only be activated when lengthy queues or traffic congestion form prior to a work zone. Sensors will activate dynamic electronic message boards at key decision points as drivers approach a work zone. Drivers will be instructed to use all lanes up to the merge point, where they will take turns to merge and form a single lane. Traffic is expected to move through the work zone more efficiently with reduced queue lengths and reduced delays. Under non-congested conditions, motorists will merge to a single lane as they normally would for a work zone.
The first use of the zipper merges will take place during spring 2024 on Interstate 81 in Shenandoah County. VDOT will perform deck maintenance on the I-81 southbound bridge over Route 600 (Saumsville Road) at mile marker 287.8. Signs related to the work zone will be placed during the week of Monday, May 6, 2024, using shoulder closures. Starting, Monday, May 13, single lane closures will be used for bridge deck work for approximately two weeks. Work will be done Monday through Friday, 8 p.m. to 7 a.m. each day.
In late May or early June 2024, the zipper merge will be used again on I-81 southbound for the bridge over Route 625 (Harman Road) at mile marker 288.1. Bridge deck work with single lane closures lasting approximately two weeks will be performed Monday through Friday, 8 p.m. to 7 a.m. each day.
Both the Route 600 and Route 625 bridges are between exit 291 at Toms Brook and exit 283 at Woodstock.
“There is a common view that merging early and waiting patiently in a single travel lane before the merge area is correct behavior,” Staunton District Traffic Operations Director Matt Shiley said. “Rushing ahead of the line in the adjoining lane can be perceived as unsafe or rude. What we are trying to achieve with the zipper merge under congested conditions is to use all available capacity of both lanes to move traffic more efficiently, reducing the delays for all.”
VDOT frequently sees traffic back-ups during daytime and nighttime work zones. Delays are updated on the VDOT 511 system, which sends alerts stating how many miles of delay exist.
Shiley said the pilot project will evaluate traffic data and in-person field experience so VDOT can see what is working and what may be improved.
“It is an ongoing process in all of our traffic operations. We have seen zipper merges work well in other states and we want to give it a chance here to help make I-81 as safe and efficient as possible,” Shiley said.
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Rebecca Barnabi
