Iowa cdl Double - Test 1
Number of questions: 20
Passing score: 80%
Acceptable number of errors: 4
This endorsement is required if the driver will pull two or three trailers. To receive this endorsement, applicants must pass a test. The test consists of 20 multiple choice questions. To pass, the applicant must answer at least 16 questions correctly. Each question has three possible answer choices. Test questions come from the Iowa Commercial Driver License Manual. Questions come from chapters covering: Driving Safely, Air Brakes (if applicable), Combination Vehicles and Doubles and Triples. The Double/Triple endorsement can be used with the Class A CDL.
To DMV Handbooks16. When operating a vehicle with a dual air brake system, the driver should:
Let the vehicle warm up before driving to ensure that the fuel reaches the engine.
Let the air compressor build up a minimum of 100 psi pressure in the primary and secondary systems before driving.
Begin driving just after the vehicle starts.