Arizona testing smart work zones along I-40 to increase safety

Feb. 5, 2021

Project utilizes a dynamic merge system, a specific type of smart work zone

In order to increase safety and mobility in highway work zones, the Arizona DOT (ADOT) is studying a smart work zone at an existing I-40 bridge project located between Flagstaff and Winslow.

A smart work zone is a traffic management system that can be controlled remotely through computer networks, portable message boards, and sensor technology to provide motorists with real-time traffic information as they approach construction work zones. This project utilizes a dynamic merge system, which is a specific type of smart work zone.

According to ADOT, the dynamic merge system is designed to mitigate the potential hazards of lane closures by altering the time to merge based on the current level of traffic. When traffic is light, electronic signs placed well ahead of the work zone encourage drivers to merge into the open lane prior to the lane closure. When traffic is heavy, the system will encourage drivers to remain in the closed lane for as long as possible in what is known as a zipper merge.

Arizona has been utilizing the zipper merge on various projects since 2016. The zipper merge works by having drivers remain in their lanes and merge just before the lane closure begins. ADOT says this is a more efficient way of moving heavy traffic through a work zone where a lane is closed.

In order to study the potential impact a dynamic merge system can have on safety and mobility in a highway construction work zone, ADOT picked an existing bridge deck rehabilitation project on I-40 at the Two Guns and Meteor Crater bridges as a test site. ADOT set up a dynamic merge smart work zone in the westbound direction and a traditional work zone in the eastbound direction in order to compare the effectiveness of a dynamic merge system.

Crash data and speed data will be gathered from the smart work zone and traditional work zone and used to evaluate the impact and inform decisions on future highway projects.