OT but technically very demanding question … Test question official test to the test engineer: 2 vehicles drive with braked trailers with automatic return. They both brake on normal road and this completely flawless. They both drive backwards and the automatic return triggers. During the brake test in the roller brake test stand the trailers are driven into the roller and then pushed back with the vehicle. d not with the other. What is it ? P.S. the technical should be technically called