South Dakota Department of Transportation improved safety on a 19-mile segment of Interstate 29 by deploying the state’s first Variable Speed Limit (VSL) system. Located between South Dakota Highway 32 in Flandreau and U.S. Highway 14B in Brookings, the corridor runs through the wind- and snow-prone Coteau des Prairies region and has historically experienced elevated winter crash rates.

The $3 million project allows SDDOT to adjust speed limits in real time based on weather, roadway, and traffic conditions. Using data from cameras and sensors that monitor temperature, visibility, wind, pavement conditions, and traffic speeds, the system lowers speed limits as conditions deteriorate and restores them as conditions improve. This approach promotes safer, more consistent driver behavior during adverse winter weather.

Implemented in November 2025, the system benefits commuters who rely on this stretch of I-29 to access jobs, businesses, healthcare services, and educational institutions in Brookings and the Sioux Falls metropolitan area. Early benefits include reduced crash risk, enhanced safety for snowplow operators and emergency responders, and clearer guidance for less experienced drivers, out-of-state travelers, and commercial vehicle operators.

By leveraging real-time data to improve decision-making on the roadway, the Variable Speed Limit system enhances safety, mobility, and reliability while helping keep a vital transportation corridor operating efficiently during challenging winter conditions.