California CDL Permit Test - Combination

Before a trip, you should ensure that air reaches all air brakes on all trailers by opening up the rear emergency line and service line shut-off valves and listening for escaping air. Close both shut-off valves before beginning to drive.

Tractor protection controls in older vehicles may be operated by levers instead of knobs. If an air supply control is set in its "normal" position, it is properly set for you to pull a trailer.

When connecting a converter dolly to a second or third trailer, the trailer height should correct. It should be slightly lower than the center of the fifth wheel.

All trailers and converter dollies manufactured on or after March 1, 1998 must have Anti-Lock Braking Systems (ABS).

Before a trip, be sure to inspect all couplings. There should be no space between the upper and lower fifth wheel.

The emergency air line controls the emergency brakes on a combination vehicle. A loss of air pressure in the emergency line will cause the emergency trailer brakes to activate.

When making a turn, be sure to steer gently and smoothly. Making a quick turn while pulling trailers is dangerous and can increase the risk of the last trailer rolling over.