A Danbury man was killed in a highway crash last night in Waterbury.  A tractor trailer was headed west on I-84 near exit 23 around 8:30pm when the driver of a Chevy Silverado failed to slow down due to traffic, rear ending the truck.  The truck driver was transported to St. Mary's Hospital for evaluation.  The other driver, 20-year old Zachary Carlson of Danbury, was pronounced dead at the scene.  Both vehicles were towed from the highway.  State Police say the accident remains under investigation. Any one with information is asked to contact Tpr Paustian #1094 at Troop A at (203)-267-2200.