CDL Combination Vehicles TestCoupling and UncouplingEasy
A driver is connecting the air lines between the tractor and trailer. Which of the following is the correct procedure for connecting the emergency (red) air line?
- AConnect the red glad hand to the blue glad hand on the trailer, then secure it.
- BConnect the red glad hand to any available glad hand on the trailer, then test for leaks immediately.
- CConnect the red glad hand from the tractor to the red glad hand on the trailer.
- DConnect the red glad hand to the service line on the trailer, then charge the system.
Show answer & explanationAnswer & explanation
Correct answer: C. Connect the red glad hand from the tractor to the red glad hand on the trailer.
The emergency (red) air line on the tractor must always be connected to the emergency (red) glad hand on the trailer to ensure proper brake system function and safety.
Why the other options are wrong
- A. Connecting red to blue would cross the air lines, leading to brake malfunction.
- B. Glad hands are color-coded and specific to their function; connecting to 'any available' is incorrect.
- D. The red line is for emergency air, not the service line, and connecting incorrectly would cause issues.
Emergency Air Line Connection
The emergency air line (red) connects the tractor's emergency air supply to the trailer's emergency brake system, allowing for automatic braking if air pressure is lost.
- Always connect red to red.
- Supplies air to release trailer spring brakes.
- Activates trailer brakes if pressure drops or lines separate.
Memory trick: Red-to-red, blue-to-blue, keeps your trailer braking true.