A tractor-trailer accident just before 6 p.m. yesterday at the 341 eastbound mile marker of I-40 in Roane County locked up traffic for hours. The Tennessee Highway Patrol says a 1999 Freightliner driven by 56-year-old Porfirio Chinchillas-Valenzuela of Shreveport, Louisiana, lost control in a curve and turned over on its side, striking the guard rail. The vehicle continued to skid for 150 feet before coming to rest and spilling its biodegradable insulation cargo. The driver was restrained at the time of the crash and was not hurt. Traffic was either stopped or down to one lane as crews cleaned up the debris. The interstate at the crash site was re-opened to regular travel around midnight. The 341 mile marker has been the scene of several tractor-trailer accidents in the past year. TDOT is about to start a project there to increase signage to warn motorists, especially tractor-trailer drivers, to slow down before taking the curve and going down the mountain toward Rockwood and Harriman.