Dedham police are seeking the public's help to find a driver in an apparent road rage incident that seriously injured a teenager.Police say a male teenager was dragged by an unknown vehicle during an apparent road rage incident at about 4:50 pm. Friday in the area of West Street at Lyons Street, and also Common Street. The teenager suffered serious injuries, police said.Police are hoping to find the driver of that vehicle. Anyone who has information or witnessed the incident is asked to call police at 781-751-9300.