An emergency structural inspection triggered the sudden closure of a critical I-75 overpass in Sterling Heights Wednesday afternoon, trapping thousands of commuters in a gridlock that stretched for more than 12 miles and stranded motorists for up to four hours during one of the busiest travel periods of the year.

The Michigan Department of Transportation ordered the closure of the I-75 overpass at Hall Road at approximately 3:15 p.m. after a routine drone inspection identified a previously undocumented crack in one of the bridge’s primary support beams. MDOT officials said the decision to close the span immediately was made out of an abundance of caution after engineers assessed photographs from the inspection.

“Our job is to protect the traveling public, and when we see something that raises a structural concern, we act,” said MDOT spokesperson Jeff Cranson. “We understand the significant inconvenience this causes, but we cannot compromise on bridge safety.”

The closure sent shockwaves through the already-congested evening rush hour network in Macomb County. Traffic on I-75 backed up to well south of 8 Mile Road, and drivers seeking alternate routes quickly overwhelmed local streets including Van Dyke, Mound Road, and Gratiot Avenue. Michigan State Police troopers were dispatched to manage traffic at dozens of key intersections.

Several motorists reported being stuck on the highway for more than three hours without moving, as GPS applications routed thousands of drivers simultaneously onto the same side streets, creating secondary gridlock throughout Warren, Sterling Heights, and Utica. Some frustrated drivers abandoned their vehicles on shoulders to find facilities or food, drawing safety warnings from troopers.

MDOT deployed a team of structural engineers overnight to conduct a full bridge inspection. Officials said the span would remain closed until engineers could confirm it was safe for travel or complete emergency stabilization work. A timeline for reopening was not provided Wednesday evening.

Commuters were advised to use M-59 as an alternate corridor and to allow significantly extra travel time Thursday morning. The closure affected both northbound and southbound lanes of I-75 through the Hall Road interchange area. MDOT said it would provide updates every six hours until the bridge was cleared for reopening.