Question When about to drive a vehicle with a dual brake system, a driver should: Answers Let the vehicle warm up to ensure the fuel reaches the engine. Wait for air pressure to build in both the primary and secondary systems. Begin driving just after the engine starts. Pump the pedal about 20 times to build pressure, then begin driving. Explanation Before driving a vehicle with a dual air brake system, allow time for the compressor to build up pressure to at least 100 psi in both systems. Take a FREE Practice Test Now This questions appears in the following tests: Mississippi Passenger ,