Oklahoma’s first Zipper Merge coming to I-35 in Pauls Valley this week

Published: 03/11/2021, 7:32 AM
Edited: 03/11/2021, 11:24 AM
(GARVIN COUNTY, Okla.) Drivers on I-35 in southern Oklahoma should get ready to “zip” when merging to help improve safety and efficiency in a busy work zone in Garvin County. Beginning this week, speed sensors in the work zone where I-35 narrows to one lane at SH-19 (mm 72) in Pauls Valley will monitor the flow of traffic and adjust the merging method. When congestion begins to build, digital message signs will instruct drivers to continue using both lanes up to the merge point and then take turns merging – alternating between the left and right lanes – into a single lane. This will most likely occur during peak travel times like weekends and holidays. It’s important to note that this Zipper Merge won’t be in effect at all times and that the new merging method won’t be used in every highway work zone statewide. The Oklahoma Department of Transportation will closely monitor how this first Zipper Merge on I-35 is working and may decide to implement more in the future. While the Zipper Merge won’t eliminate all traffic tie-ups due to highway construction, the department expects the change to significantly improve the travel conditions on I-35 where implemented. Unlike the more traditional early merge used in Oklahoma work zones, where all vehicles are directed to move into one lane well in advance of the closure, the Zipper Merge makes full use of the available roadway and helps reduce a long lines of traffic backing up in a single lane while the adjacent lane sits unused. “The Zipper Merge has been used very successfully in other states nationwide and this location on I-35 in Pauls Valley will be our first test in an Oklahoma work zone,” ODOT Chief Engineer Brian Taylor said. “The Zipper Merge is a change from how many of us are used to merging in work zones, so this will be a learning process and a time to show other drivers some patience and grace.” The late merge concept is commonly known as the “Zipper Merge” because the movement of two alternating lines of cars merging into one lane resembles the interlocking teeth of a zipper on a piece of clothing. The method has been generally well-received because it is intuitive and requires drivers to be cooperative, rather than competitive. A video produced by ODOT to explain the Zipper Merge can be found on the agency’s Vimeo webpage https://vimeo.com/odot/videos. “I know it may be frustrating when we think someone is cutting in line on the highway, but the Zipper Merge method actually moves large volumes of traffic through a choke point more efficiently,” Taylor said. “If we can all be courteous and patient with other drivers, we all benefit.” Until 2018, state law in Oklahoma required drivers in all highway work zones to merge a certain distance from the lane closure with “State Law, Merge Now” signs posted in construction areas as a reminder. While this method generally works well in less-congested work zones, a lane closure on a busy interstate like I-35 can become more problematic as large volumes of cars and commercial trucks all try to move into one lane as traffic quickly slows or even comes to a stop. A recent change in state law now allows other work zone arrangements that meet national standards. This means the Zipper Merge can be used where appropriate but is not required in all work zones statewide. Drivers must continue to observe the signage in each work zone and merge as directed. Along with the flashing digital signs, orange work zone signs can also be used to alert drivers that a Zipper Merge is ahead and to direct traffic to use both lanes and take turns merging. The $3.5 million project to rehabilitate the I-35 bridges over SH-19 in Pauls Valley began in spring 2020 and is being performed in two phases. The first phase included rehabilitation of the northbound bridge and was completed in late 2020 so the interstate could be fully open for holiday travel. The second phase to rehabilitate the southbound bridge is expected to continue through summer 2021. Silver Star Construction, of Moore, is the contractor on the job.
Digital message signs connected to real-time traffic sensors will direct drivers to use both lanes and perform a Zipper Merge where north and southbound I-35 narrow to one lane at SH-19 in Pauls Valley. While this is the first Zipper Merge used by the Oklahoma Department of Transportation, it has been used successfully in many other states.


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