A single vehicle accident just after 4 a.m. this morning on I-40 in Cumberland County tied up traffic for a few hours but no injuries were reported. Troopers say a United States Postal Service tractor-trailer operated by 51-year-old Timothy Turner of Sparta was traveling west at the 313 mile marker when the drive axle broke causing it to veer off the road. The rear double trailer flipped onto its side and the tractor jackknifed. Turner was restrained at the time of the accident.