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.

If your trailer begins to drift while you are backing, you should correct the drift immediately by turning the top of the steering wheel in the direction of the drift.

Bobtail tractors are tractors that are not attached to any semitrailers. When operating a bobtail, you should be aware that stopping can be difficult and that it will take a longer distance to bring the bobtail to a complete stop than it would a tractor attached to a loaded semitrailer.

Tractors without semi-trailers are referred to as bobtail tractors. Operating a bobtail tractor requires drivers to exercise caution.

To lower the risk of a rollover, load your cargo as closely to the ground as possible. To further reduce this risk, take curves and corners slowly.

On newer vehicles, the trailer air supply control is an eight-sided red knob. It's used to control the tractor protection valve.

Before a trip, ensure that air in the air brake system reaches all trailers. Do this by waiting for air pressure to build, then sending air to both the emergency and service lines and opening the shut-off valves on the rear of the last trailer. If air escapes from the shut-off valves in the rear of the combination, the air is being supplied to the entire vehicle.

When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is known as off-tracking, or "cheating."

While inspecting a coupling, you should go under the trailer and look into the back of the fifth wheel. Ensure that the fifth wheel jaws are secured around the shank of the kingpin.

Combination vehicles require more space on the road than other vehicles. When entering or crossing traffic while driving a combination vehicle, it is especially important that there is a large enough gap in traffic for you to safely do so.

When a combination vehicle is lightly loaded, it may have poor traction. It is very easy for wheels to lock up on lightly-loaded vehicles when they are being stopped.

When driving a tractor-trailer combination equipped with an Anti-Lock Braking System (ABS), you should brake in the same manner that you would if operating a vehicle without ABS.

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.

Tractor protection controls in older vehicles may be operated by levers instead of knobs. If an air supply control is set in its "emergency" position, the air supply will be stopped and the trailer emergency brakes will be applied.

Having an Anti-Lock Braking System (ABS) on only the trailer, or even on just one axle, will still provide a driver with additional control over the trailer when braking.

Rollovers can happen when a combination vehicle is turned too quickly. To help prevent the risk of rollover, it is important to keep the vehicle's center of gravity low by loading cargo as close to the ground as possible.

If your trailer starts to skid while you are braking, you should release the brakes and allow them to begin to regain traction. Once its wheels have regained their grip on the road, the trailer will begin to straighten out and follow the tractor.

Due to the "crack-the-whip" effect caused by rearward amplification, changing lanes too quickly in a combination vehicle can result in a rollover.

Before coupling together a tractor and a trailer, you should make sure the trailer is at the proper height. If the trailer is too low, the trailer nose may be damaged. If the trailer is too high, it may not be able to couple correctly.

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