Two Clinton residents were killed and two were badly hurt in a traffic accident Sunday afternoon near Mount Saint Clare College in Clinton. A car driven by 77-year-old Robert Adler of Clinton collided with another car and ended up on its roof. Adler was killed. Also killed was 61-year-old Diane Adler of Clinton. Two passengers in the car were injured. 54-year-old Dale Wheeler is in serious condition at University Hospitals in Iowa City and 58-year-old Joan Greene is in critical condition. Both Wheeler and Greene are from Clinton. The accident is under investigation.