Combination
All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Missouri Commercial Driver License Manual. Section 6 provides the information needed to safely operate tractor-trailers, doubles, triples, and straight trucks with trailers. The test is made up of 20 multiple-choice questions, and applicants will need to correctly answer a minimum of 16 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.
Number of Question
Passing Score
1. When coupling a trailer, you should:
Explanation
When coupling air brake hoses, you should make sure the proper pairs of gland hands are connected. They are sometimes color-coded to help drivers avoid mistakes. Typically, blue is used for service lines and red is used for emergency lines.
2. If a trailer begins to skid, it is best for the driver to:
Explanation
If your trailer begins to skid, you should release the brakes to regain traction. The trailer will begin to straighten out once the wheels begin to grip the road again.
3. What is a tractor protection valve?
Explanation
A tractor protection valve keeps air in a tractor or truck air brake system should the trailer break away or develop a bad leak. The valve will close automatically if the pressure drops to an unsafe level.
4. When braking while pulling a trailer equipped with anti-lock brakes, you should:
Explanation
When driving a tractor-trailer combination that is equipped with an Anti-Lock Braking System (ABS), you should brake in the same manner that you would if the vehicle was not equipped with ABS.
5. When backing up while coupling a trailer, the tractor should be positioned:
Explanation
When backing up to couple a trailer, you should position the tractor directly in front of the trailer. Trying to couple while backing at an angle could cause the trailer to move and the landing gear to break.
6. When driving with trailers, you should:
Explanation
To reduce the risk of tipping over when driving with a trailer, you should steer gently and smoothly. Avoid making sudden movements.
7. All trailers made after ____ must be equipped with Anti-Lock Braking Systems (ABS).
Explanation
