Semi-Truck and Trailer Plunge Down Mountain Cliff After Losing Control Colorado Rockies — A terrifying accident unfolded on a snow-covered mountain highway when a semi-truck and its trailer lost traction on an icy stretch of road and plunged down a steep cliff, disappearing from view as debris and snow cascaded down the mountainside. The aftermath was captured by a nearby motorist who stopped just short of the damaged guardrail. The video shows the immediate scene following the crash, with the g