Police say the driver of a tractor trailer on northbound I-91 fell asleep early Friday, ran off the road and crashed into a patch of boulders, shutting down a portion of the highway for several hours.

Vermont State Police responded to the crash between Exits 7 and 8 at 3:17 a.m. The driver, Thomas Moore 59, of Hamden, Connecticut, was not injured.

Police say Moore initially ran off the shoulder of the road. When he tried to correct his course, he traveled back across the interstate and into the median, hitting the boulders.

The front end of the truck was damaged extensively.

The crash shut down one lane and disrupted morning traffic. Police said all lanes were open by 9 a.m.

A crew from Vermont Department of Transportation remained on the scene to clean up a small oil spill.