Interstate 91 southbound was closed in Enfield during rush hour after a car carrier struck the Route 5 overpass at exit 49, state police said.
The accident happened around 5 p.m. and caused a mess in the southbound lanes.
Police began to allow cars to pass the accident on the right-hand shoulder, but traffic remained congested for drivers traveling southbound, police said.
State police said no injuries have been reported.