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6-Inch Pavement Markings

Six-Inch-Wide pavement markings on I-496 in Lansing.
Department of Transportation

6-Inch Pavement Markings

As connected and autonomous vehicles (CAV) become more prevalent, road agencies, like MDOT, understand the future need for changes to traffic control devices such as signs and pavement markings. Why do we need changes to traffic control devices? CAV use technology such as cameras and machine-vision, to detect their location on the road, speed, and distance of nearby objects. Many new vehicles now come equipped with autonomous technologies such as automatic emergency braking, adaptive cruise control, lane departure warning, and lane-keeping assistance. These systems are designed to alert road users to potential conflict points or keep motorists in their lanes. Road departure crashes, including distracted and impaired driving, account for approximately half of all highway fatalities. CAV technology can significantly reduce these types of crashes – saving lives and reducing injuries.

For CAV technology to be successful, good and consistent pavement markings are needed. Wider lane markings and edge lines make it easier for cameras and sensors to read the road. Research has shown that 6-inch-wide pavement markings consistently improve machine vision detection under adverse visibility conditions and can improve detection on high-speed roads where potential conflicting signals may confuse such systems from detecting pavement markings. Research has also shown that 6-inch-wide pavement markings are good for human drivers, too.

Currently, Michigan uses 6-inch-wide edge lines on state trunklines (I, M and US routes). In response to the need for wider lane markings and proposed changes to national standards, MDOT moved forward with 6-inch-wide lane markings on all freeways in summer 2020. MDOT contractors also placed white dotted line extensions on exit and entrance ramps to provide further lane guidance to road users. The additional $200,000 investment for 6-inch lane markings and $450,000 for dotted line extensions were done as part of MDOT’s annual pavement marking restriping projects. In 2021, MDOT started changing both white and yellow lane lines on non-freeways to 6-inches-wide. This effort will take three to four years.

These projects will improve safety and guidance on Michigan trunklines for both human and machine-vision drivers.