2005 Commercial Driver’s License Manual If your vehicle does not have automatic air tank drains, drain your air tanks at the end of each working day to remove moisture and oil. Otherwise, the brakes could fail. Never leave your vehicle unattended without applying the parking brakes orb iibchocking the wheels. Your vehicle might roll away and cause injury and damage. Subsection 5.4 Test Your Knowledge 1. Why should you be in the proper gear before starting down a hill 2. What factors can cause brakes to fade or fail 3. The use of brakes on along, steep downgrade is only a supplement to the braking effect of the engine. True or False 4. If you are away from your vehicle only a short time, you do not need to use the parking brake. True or False 5. How often should you drain air tanks 6. How should you brake when you drive a tractor-trailer combination with ABS 7. You still have normal brake functions if your ABS is not working. True or False These questions maybe on your test. If you can’t answer them all, reread subsection 5.4.