A two car accident on I-684 NB at about 5 p.m. today resulted in a pretty large traffic backup on the interstate at the height of the rush hour. Katonah Fire Department, with KBHVAC, was dispatched today to the accident, which occurred in the left lane of the highway on the overpass to the Saw Mill River Parkway. One of the occupants complained of chest pain and was transported by KBHVAC. Katonah units remained on scene, creating a safety zone and directing traffic until the cars were towed and the ambulance left. Units were back in service by 5:30 p.m.