A big rig driver who crashed off Interstate 5 in Cottonwood Tuesday night was dead when medics arrived. At 6:20PM the unidentified driver of a Freightliner hauling a 53-foot Wal-Mart box trailer was southbound when the tractor-trailer left the pavement north of the Main Street exit, went down an embankment and up the other side, coming to rest in a stand of small oak trees. The CHP says the driver may have suffered a medical emergency prior to running off the road. There was no sign of drugs or alcohol.