Question When leaving a vehicle unattended, a driver should: Answers Always set the parking brake. Only set the parking brake if the vehicle is parked on a slope. Deflate the tires by 10 percent. Explanation Always apply the parking brake when leaving your vehicle unattended. This questions appears in the following tests: Alabama Air Brakes Arizona Air Brakes Arizona Air Brakes California Class B Knowledge Test California Class B Knowledge Test Hawaii Air Brakes Iowa Air Brakes Louisiana Air Brakes Maine Class A Knowledge Test Maine Air Brakes Maryland Class A Knowledge Test Michigan Class B Knowledge Test Mississippi Bus Montana Air Brakes North Carolina Class B Knowledge Test North Carolina Air Brakes Oklahoma Class A Knowledge Test Rhode Island Class A Knowledge Test South Carolina Air Brakes South Dakota Air Brakes Washington Air Brakes Wyoming Class B Knowledge Test