US-23 Flex Route

As part of state’s first active traffic management (ATM) project, the Michigan Department of Transportation’s US-23 Flex Route project creates a safer and more timely driving experience for Michigan drivers. As the prime consultant, HNTB was the lead design firm for the planning, design, design assistance during construction and system management of the intelligent transportation system (ITS).

The main goals of the US-23 Flex Route project were travel time reliability and safety. Dynamic shoulder lanes reduced congestion during peak periods and special events, improved travel time reliability by providing consistent conditions and reduced crashes by providing speed advisories and advance notice of conditions ahead. The dynamic shoulder use strategy provides an additional lane of traffic during the peak periods, special events and unexpected congestion. The variable speed advisory and queue warning strategies convey speeds to reduce stop and go conditions and messages, such as “stopped traffic/2 miles ahead.” Dynamic lane use combined with dynamic shoulder use direct traffic safely around major incidents to improve traffic flow and safety of first responders.

The US-23 Flex Route uses overhead lane control gantries equipped with various ITS equipment to facilitate the following ATM strategies: dynamic shoulder use, dynamic lane control, variable speed advisories and queue warning. A real-time truck parking information and management system (TPIMS) features the delivery of real-time truck parking availability information to truck drivers along the US-23 Flex Route, and the overheight vehicle detection system provides a warning for overheight vehicles to exit US-23 to avoid low bridges on the corridor.

The project was packaged with several large road and bridge projects to construct the shoulder, drainage, and widened bridges to facilitate part-time shoulder use. HNTB was the prime consultant for bridge design of 6 Mile Road, 8 Mile Road, and North Territorial Road, and the as-needed construction engineering and inspection (CEI) firm for roadway construction.