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 The trailer hand valve should be used: Answers To test the trailer brakes. To check the connection between the trailer and tractor. To accelerate. To test the lights on the trailer. Explanation The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. It should be used only to test the brakes. Take a FREE Practice Test Now This questions appears in the following tests: Kansas Tank , Georgia Combination , North Carolina Combination , West Virginia Combination ,