KINGSPORT — The northbound lanes of Interstate 81 were closed for two hours Tuesday afternoon when two tractor-trailers collided. According to a news release from Kingsport Police Department Public Information Officer Tom Patton, at approximately 3:30 p.m., officers from the KPD’s Patrol Division and Traffic Unit responded to a motor vehicle collision involving two tractor trailers on Interstate 81 at mile marker 58.After a thorough analysis of the crash scene and a review of statements given by both drivers and three independent witnesses, investigators were able to determine that the following occurred:A 2001 International tractor-trailer, driven by Ram Avtar, Longueil, Quebec, and owned by Papineau International, was northbound on Interstate 81 at the 58 mile marker in the right lane.