Active traffic management (ATM) aims to dynamically manage recurrent and non-recurrent congestion based on prevailing and predicted traffic conditions. Researchers analyzed the effectiveness of the US Route 23 Flex route opened by Michigan Department of Transportation (MDOT) in 2017 to mitigate peak-hour congestion, reduce incident response times, and improve safety. The Flex route uses the corridor’s 11-foot wide inside shoulders as dynamic lanes over a length of 8.5 miles. Researchers analyzed the performance of the Flex route, the safety of the adjusted roadway, driver perceptions, and the costs and benefits provided. Operational performance data was collected using various sources including probe vehicle data, microwave vehicle detection system reports, permanent traffic recorder data, ATM reports, and incident clearance data. Real-world safety data was collected before the lane was installed, from 2012 to 2015, and after, from 2018 to 2019.

The capital costs of the Flex route installed on US-23 (Table 1) totaled $60 million, with $3 million going towards software module, $17 million going towards ITS construction, and $40 million going towards shoulder construction, as reported by MDOT in 2021.

Table 1. Capital costs of the US-23 Flex route

The annual operation and maintenance (O&M) costs were estimated by the FHWA’s Tool for Operations Benefit/Cost Analysis (TOPS-BC) Version 4.0., which includes $350,000 for software module, $350,000 for ATM Traffic Operations Center hardware, $1 million for harden shoulder (2.5 percent of the capital costs of shoulder construction), and $340,000 million for ITS (2 percent of the capital costs of ITS construction).