Traffic TopicsDoes the Zipper Merge

threaten our way of life?

Ken E. Johnsonken.johnson@state.mn.us

651-234-7386Office of Traffic, Safety and Technology

• Recent media attention:• “Turns out those “jerks” were

right…”– Pioneer Press 5/17/10

• “I’ve seen a threat to our very way of life – The Zipper Merge” – Joe Soucheray 5/23/10

Zipper Merge

Why Zipper Merge?What are the benefits?What have been the problems?Where are we and what is

Mn/DOT doing?

Zipper Merge:

Merging behavior where drivers are encouraged to use both lanes prior to defined merge area

Active Zipper Merge:

Sensors and intelligence telling drivers when to use the Zipper Merge

Passive Zipper Merge:

Signs or PCMS notifying drivers to use Zipper Merge when backups occur

Terminology

Why Zipper?Existing Merging Problems

• Backups• Can extend beyond the advance warning signs when

motorists queue up in a single lane• Can block access or interchanges

• Rear end crashes caused by:• Traffic flow disruptions caused by erratic merging

along the entire length of the queue during backups• Speed differential between lanes

• Increased Road Rage against those “cheaters”• Self-appointed “cops” straddling lanes

• It’s perfectly legal…

This scenario commonly occurs duringThis scenario commonly occurs duringlane closureslane closures

Why Zipper?

Preferred Traffic Flow — UtilizingPreferred Traffic Flow — UtilizingEqual Lane OccupancyEqual Lane Occupancy

Why Zipper?

2004 Dynamic Late Merge Study

• Four Deployments:Four Deployments:

• I-494 Northbound in PlymouthI-494 Northbound in Plymouth

• I-494 Southbound in PlymouthI-494 Southbound in Plymouth

• US 52 in St. PaulUS 52 in St. Paul

• I-35 around LakevilleI-35 around Lakeville

• Evaluation of 2004 Dynamic Late Merge System Evaluation of 2004 Dynamic Late Merge System by URSby URS

Why Zipper?

Dynamic Late Merge Study (2004)Dynamic Late Merge Study (2004)Before and After DeploymentBefore and After Deployment

Why Zipper?

http://www.dot.state.mn.us/trafficeng/workzone/doc/MnDOT%20Video%20DLMS.mpg

Findings and Results of 2004 Dynamic Late Merge Study

• Not enough info to evaluate crashes but it was clear:Not enough info to evaluate crashes but it was clear:• Reduced aggressive drivingReduced aggressive driving• Less confusionLess confusion

• Queue Lengths were reduced by 40%Queue Lengths were reduced by 40%• Lane occupancy increased everyday during congestion - Lane occupancy increased everyday during congestion -

reached near equal lane occupancy after short durationreached near equal lane occupancy after short duration• Throughput not increased – 1600 vphThroughput not increased – 1600 vph

Why Zipper?

Passive Zipper Merge• Signs added:Signs added:

• USE BOTH LANES DURING BACKUPSUSE BOTH LANES DURING BACKUPS• TAKE TURNS AT MERGETAKE TURNS AT MERGE

• Used over the past few years successfullyUsed over the past few years successfully• I-35 between Pine City and HinckleyI-35 between Pine City and Hinckley• I-35 near Faribault and OwatonnaI-35 near Faribault and Owatonna• Hastings bridge maintenance projectHastings bridge maintenance project• State Highway 61 in St. Paul ParkState Highway 61 in St. Paul Park• I-494 in WoodburyI-494 in Woodbury

• Similar benefits to what was found in the DLMSSimilar benefits to what was found in the DLMS

Why Zipper?

ExpectedBenefits

• Speed differential reduced• No Zipper - 1 lane stop and jerk and 1 lane fast• Both lanes moving at same speed

• Reduced length of queue• Theoretically up to 50%• Reduced blocking of accesses and interchanges

• Fair• Both lanes are equally disadvantaged by the backup• Reduced Road Rage

• More protection for work area when both lanes have queues

• But – it won’t get you through faster

Problems? • Inconsistent application

• Some mixed messages• Advance warning sign that tells the driver which

lane is closed• Some road rage issues even at locations signed for Zipper• Online Community Surveyed

• Statewide Work Zone Safety Committee• We know it works, what can we do?

• 80% Early Mergers• 2/3 unhappy about late mergers• 14% would block late mergers

• 40% Zipper Merge concept is new to them

Where are we?What is Mn/DOT doing?

• Decision made:• Work to change typical driver behavior to do the

Zipper Merge as standard• When driving highway speeds – merge early• When backups occur – use both lanes

• How:• Public education effort• More standard implementations of Zipper Merge

• Construction• Maintenance• In Metro – will implement when volumes

exceed 1800 vph (Lane Closure Manual)

Layouts…

Layouts…

Where are we?What is Mn/DOT doing?

• CO Communications:• Working to develop Public Education blitz

• CO Traffic:• Created layout for Field Manual• Trying to get funding for signs for Maintenance

• Construction:• Received Destination Innovation Funding to

implement for 2011 construction projects• Active Zipper Merge systems in Metro projects• Stopped Traffic Ahead systems in Greater MN

projects• Maintenance:

• Implement Zipper Merge where appropriate

Resources…

• Handout available on web:• Late Merge…the Zipper System• Google mndot zipper

• Layouts in the Field Manual

• Dynamic Late Merge System information• http://www.dot.state.mn.us/trafficeng/workzone/wzreports.html• Dynamic Late Merge System Evaluation• DLMS Video

Not the only ones

Taupo, New Zealand – Courtesy of Derrick Dasenbrock

Final thought…

When you go to the grocery store – what line do you get into? Why are highway projects different?

Questions?