EXCLUSIVE

Robert Carradine -- the star of "Revenge of the Nerds" -- was involved in a horrifying car accident with a semi-truck ... TMZ has learned.

The head-on collision occurred last week on a Colorado highway at 3 PM. According to the police report -- obtained by TMZ -- Carradine crossed the dividing line and slammed into the truck.

Firefighters removed Carradine from his car and he was rushed to a nearby hospital with "incapacitating" injuries.

Carradine's wife was in the car and also injured.

We called Carradine's rep to find out how he's doing ... so far no word back.