More than six hours after the northbound lanes of Interstate 81 were closed by a multi-vehicle crash, the highway has reopened.

The crash near exit 45 (College Street) occurred when a tractor-trailer driver failed to notice traffic in front of him slowing and struck the rear of a flatbed truck around 8:30 a.m.

It took more than an hour to extricate the driver of the tractor-trailer, Donald Charlton, 64, of Martinsburg, from the wreckage. He was rushed to an area hospital, where state police said he was in stable condition Monday aftenroon.

Traffic was still being pulled off I-81 North at the Allen Road, Exit 43 interchange as of 1:30 p.m. while site clean-up continued.

Affected motorists were being re-routed back onto the highway at northbound ramp of Exit 44, avoiding major tie-ups in downtown Carlisle through most of Monday, borough police said.