Do you currently have car insurance? Yes I have insurance. Great, you're all set! Click here if you still want to compare rates. No, I need insurance and I want to compare options. Before you start the test, please answer the following question regarding your insurance status. Without insurance you will not be able to drive in California Question What kind of force must emergency brakes use? Answers Air pressure Mechanical Heavy Electrical Explanation Because air pressure can eventually leak away, the emergency brakes in an air brake system must be held on by mechanical force. Take a FREE Practice Test Now This questions appears in the following tests: New Jersey Knowledge Test Class B , West Virginia Knowledge Test Class B , Maryland Air Brakes , Pennsylvania Air Brakes , South Carolina Air Brakes , South Dakota Air Brakes , Utah Air Brakes ,