State Police are investigating a three car crash that happened in Bethlehem on Friday afternoon.  A 28-year old Watertown man was headed north on Flanders Road near Thomson Road and rear ended a 58-year old Bethlehem man's car, which pushed into the rear of a 77-year old Bethlehem woman's vehicle.  The older man was transported to Waterbury hospital for treatment of serious injuries.  No other injuries were reported.  This crash is an ongoing investigation. Any witnesses are asked to contact Troop L at 860-626-7900.