Cpl. Edwin Ritter says officers believe the rail was damaged by a tractor-trailer that left the scene. Ritter says the damage to the guardrail left a large section of it in the roadway, and several motorists were unable to avoid it.
All motorists heading northbound on I-85 were diverted to I-985.
The cable wire is part of a large section of the cable guard rail system that runs along the median of the interstate.
The road was closed for a time just before daybreak.

http://accesswdun.com/article/2011/7/240265