Zipper Merge Pilot Project
The City launched a zipper merge pilot project at two construction zones in 2015.
What is a zipper merge?
When a lane is closed for construction, a zipper merge occurs when drivers use both lanes until reaching a defined merge point. At the merge point drivers then take turns merging into the open lane in a "zipper" like fashion.
What's the purpose of using a zipper merge?
The goals of using the zipper merge are:
- to reduce the length of the traffic queue waiting to enter the construction zone, which can reduce congestion at intersections leading up to the closure, and
- to encourage similar speeds in both lanes at the merge point for safety. Speed differentials, or the difference in travelling speeds between vehicles, are a significant risk factor in motor vehicle collisions.
How will motorists know they should zipper merge?
To notify motorists that they should use the zipper merge technique, Variable Message Sign (VMS) boards will be added to the existing work zone traffic control displaying messages that encourage drivers to use both lanes until reaching the defined merge point and to take turns merging. Motorists are reminded to merge only when it is safe to do so.
The VMS boards will look like this:
What are the next steps?
The City's Public Works Department monitored and collected data during the pilot project to determine the zipper merge's effectiveness and to assess driver behaviour. A marginal increase was observed in the use of the closed lane however generally there was minimal benefit. At this time no further zipper merge trials are planned however should a suitable situation arise where the zipper merge could be of benefit, Public Works may employ this type of setup.
- Zipper Merge Demonstration Courtesy: Minnesota Department of Transportation