Innovation Spotlight

Innovation Spotlight: Dynamic Zipper Merge

For most, the term “dynamic zipper” is a funny name with no significance, but for the I-40 Davie County Project team, it is the name of an innovative system that improves the traveling public’s experience on the bustling I-40.

Introduced by project owner North Carolina Department of Transportation in 2019, the Dynamic Zipper Merge is a system that consists of both speed sensors and digital message boards. The system features seven speed sensors spaced a half-mile apart and eight changeable message signs.

The apparatus uses advanced coding technology to display important messaging based on the speed of the traffic. If traffic is flowing smoothly, the message boards will tell drivers which lane is closed ahead. If congestion is present, the message boards will say that traffic is slow “x” miles ahead. In the event of the latter scenario, the system seeks to reduce the queue by displaying a ‘use both lanes to merge point’ message.


Flatiron’s I-40 Davie County Project

As its name suggests, this type of merge is intended to work like a zipper. By taking turns at the merge point, drivers experience smoother merging conditions, which reduces traffic backups and the amount of time it takes to go through the merge.

The innovative merge system reduces the confusion between drivers who think they should merge early versus those who want to use the open lanes for as long as possible.


Flatiron’s I-40 Davie County Project consists of a 6.5 mile stretch of highway. The project scope is primarily shoulder strengthening both east and west bound with 12 edge-of-travel-way drainage areas.

Additionally, there are two main line bridges in the area that are being demolished and reconstructed. The project is anticipated to be complete in late 2021.


Flatiron’s I-40 Davie County Project

A great assist to travel planning, the Dynamic Zipper Merge also features a lane closure device compatible with Google Maps, Apple Maps and Waze. This component of the innovation uses satellite technology to communicate live updates to these map service providers, giving users more accurate travel times and current traffic conditions.

The presence of the Dynamic Zipper Merge in Davie County is one of the first uses of this technology in North Carolina. Although the average person driving by may not be able to distinguish it from any other roadside message board, the unseen speed sensors, satellite technology and programming of the system classify it far more advanced than the average roadside digital message board.


The Dynamic Zipper Merge is managed by Carolina Traffic Devices, a South Carolina-based traffic control contractor. Outsourcing the management of the system allows the Flatiron project team the ability to focus solely on the construction elements of the project with the peace of mind that these extra safety measures are being taken to protect the traveling public.

“The Dynamic Zipper Merge technology allows motorists to know the upcoming roadway conditions. This helps eliminate last-minute braking, the cause of most highway traffic accidents,” says Mary Nous, I-40 Davie County Field Engineer. “We believe the system helps significantly to reduce the potential of traffic accidents.”

In essence, the Dynamic Zipper Merge is a smart system that embraces Innovation to deliver safety and convenience to travelers.


It’s another example of how Flatiron benefits from the application of innovative technology—a system with potential benefits for future highway projects.


Jalie Creech
Marketing & Communications

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