US-23 Flex Route

As part of Michigan’s first active traffic management (ATM) project, US-23 Flex Route, HNTB served as the prime consultant and lead design firm for the planning, design, design assistance during construction, and system management of the intelligent transportation system (ITS). This 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.

The US-23 Flex Route uses overhead lane control gantries equipped with various intelligent transportation system (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 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 corridor.

The main goals of the US-23 Flex Route project are 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 will provide an additional lane of traffic during the peak periods, special events and unexpected congestion. The variable speed advisory and queue warning strategies will 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 will direct traffic safely around major incidents to improve traffic flow and safety of first responders.