New Mexico CDL Permit Test - Combination

Trailers built before 1975 are not required to have spring brakes. When parking a trailer without spring brakes, be sure to use wheel chocks to prevent the trailer from rolling.

Tractors without semi-trailers are referred to as "bobtail tractors." Bobtail tractors are difficult to operate and drivers must exercise caution.

In vehicles equipped with an automatic tractor protection valve, the valve will pop out if air pressure drops to a level between 20 and 45 psi. When the valve pops out, the protection valve will close, stopping the flow of air.

More than half of all accident-related truck driver deaths are a result of truck rollovers. To help prevent a rollover, be sure to load cargo low to the ground and centered on your rig. Take corners slowly and carefully.

When driving a tractor-trailer combination that is equipped with an Anti-Lock Braking System (ABS), you should brake in the same manner that you would if the vehicle was not equipped with ABS.

Making a sudden lane change can be dangerous while driving a combination vehicle. You can avoid the need to make a sudden lange change by looking down the road for upcoming obstacles that will require you to change lanes.

If you are operating a vehicle built before 1998 and are unsure if the trailer has an Anti-Lock Braking System (ABS), you can check under the trailer for wheel speed sensors coming from the back of the brakes.