Work Zone Mobility and Safety Program
Photo collage: temporary lane closure, road marking installation, cone with mounted warning light, and drum separated work zones.
Office of Operations 21st Century Operations Using 21st Century Technologies

Best Practice

BEST PRACTICE:

G4−9: Zipper Merge

DESCRIPTION:

When a lane is closed in a construction zone, a zipper merge occurs when motorists use both lanes of traffic until reaching the defined merge area, and then alternate in "zipper" fashion into the open lane. The Minnesota Department of Transportation (MnDOT) has implemented the use of the zipper merge in congested lane reductions caused by maintenance and construction activities. Standard layouts have been designed and are available in the document Temporary Traffic Control Zone Layouts Field Manual (February, 2011), which is part of Minnesota's Manual on Uniform Traffic Control Devices (MUTCD). Both passive (static signs) and active (intelligent work zone) systems are used to implement the zipper merge. MnDOT implemented an educational campaign through the Minnesota Drivers Manual and an advertising effort.

More information is available at http://www.dot.state.mn.us/zippermerge/ and
http://www.dot.state.mn.us/trafficeng/workzone/wzreports.html − see Dynamic Late Merge System.

REASON(S) FOR ADOPTING:

To improve safety in congested areas where lane closures are caused by maintenance and construction activities.

PRIMARY BENEFIT(S):

More even lane use approaching a lane reduction. Reduced speed differential between lanes. More predictable driver behavior. Reduced length of queue (up to 40%).

MOST APPLICABLE LOCATION(S)/PROJECT(S):

Lane reductions with flow ≥ 1500−1800 vehicles per hour.

STATE(S) WHERE USED:

Minnesota

SOURCE/CONTACT(S):

Ken E. Johnson, Work Zone & Pavement Marking Engineer, Minnesota DOT
Phone: (651) 234−7386
E−mail: ken.johnson@state.mn.us

Ted Ulven, Work Zone Standards Specialist
Minnesota DOT
Phone: (651) 234−7058
E−mail: ted.ulven@state.mn.us

Craig Mittelstadt, Construction and Innovative Contracting
Minnesota DOT
Phone: (651) 366−4222
E−mail: craig.mittelstadt@state.mn.us

Office of Operations