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Flex Route

Flex Route on US-23 in University Region.
Department of Transportation

Flex Route

The flex route system is a lane control system that uses overhead signs, cameras, and electronic message boards to let drivers know when an additional lane is available for use during morning and afternoon peak travel periods. Flex Route technology helps manage congestion and improve safety for highways that frequently experience traffic congestion during peak travel periods.

Drive the Flex Route

Flex Route Locations

  • Completed: US-23 between M-14 and M-36 (9 Mile Rd.) in Washtenaw County
  • In Construction: I-96 from Kent Lake Road to the I-275/I-696/M-5 interchange in Oakland County
  • In Design: US-23 extension from south of M-36 (9 Mile Rd.) to the I-96/US-23 interchange in Washtenaw County


MDOT describes what Flex Route is and how it will help with periods of peak travel on US-23 in Livingston and Washtenaw counties, and other possible areas in Michigan.

How do MDOT Flex Routes work?

MDOT's Flex Routes are monitored by the department's Transportation Operations Centers (TOC). The TOCs are a seven-day-a-week operation that houses dispatchers from MDOT and Michigan State Police. The agencies share resources and information by monitoring traffic sensors, distress calls and video feeds from closed-circuit TV cameras. They also coordinate their efforts with law enforcement agencies and other transportation officials.

This includes an intelligent lane control system consisting of overhead signs, cameras, and electronic message boards, which TOC employees monitor and adjust as needed. If a traffic condition develops, the TOCs will adjust the Flex Route through electronic lane control signs mounted above each lane. These signs show motorists which lanes are available and provide the recommended speed for the current travel conditions.

Additionally, traffic incidents are managed with assistance from MDOT’s Freeway Courtesy Patrol and several new crash investigation sites that are strategically located along the corridor.

Why not just add another lane?

A 24-hour fix simply is not necessary on corridors that typically experience traffic slowdowns only during regular peak travel periods. It is more cost-effective to use the shoulder as a temporary third lane than it would be construct a third lane. Employing Flex Route technology increases capacity within the existing infrastructure for less money. 

Using the Flex Route

Flex Route with green arrow showing shoulder is open.
Green Arrow: Shoulder is open and Flex Route is available as a third lane.
Flex Route showing the posted speed limit.
Speed is continuously monitored for traffic slowdowns.
Flex Route showing and incident board directing traffic.
Yellow chevron/merge signs tell motorists to move over to avoid incidents.
Flex Route showing the shoulder is closed with a red X.
Red X: Shoulder is closed and Flex Route is not to be used.
Flex Route with crash speed posting.
Recommended speeds are posted to decrease potential for crashes.
Flex Route showing a blocked lane ahead.
Signs provide motorists with information, such as a crash or blocked lanes ahead.