Correctly following the steps to couple and uncouple trailers is vital to safely operating a combination vehicle. After connecting the air lines to the trailer while coupling, you should supply air to the trailer.

A vehicle's weight is an important factor affecting its stopping distance. The heavier a vehicle is, the more work the brakes will need to do to bring it to a complete stop.

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

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.

While baffles in a tank inhibit forward and backward surge, they do not prevent side-to-side surge. Surge to the sides can cause rollovers.

Roads are particularly slippery when it first begins to rain. The water mixes with oil drippings on the road that have not yet washed away, creating a slippery and dangerous mixture.

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.

Unless your engine runs a pump for product transfer, turn it off when loading or unloading a compressed gas tank. If you do use your engine to run a pump, you should turn the engine off after the product transfer but before unhooking the hoses.

Before starting down a hill, decelerate and shift down into a gear that will allow you to control your vehicle without braking too hard. Using too much brake when driving downhill can cause the brakes to overheat, reducing the braking power.

In wet conditions, a lack of spray coming from the tires of other vehicles indicates that ice has formed on the road. Be especially cautious when traveling under wet conditions in freezing weather.

The first hazardous materials class includes explosives such as ammunition, dynamite, and fireworks.

Except when parking briefly to perform necessary functions for vehicle operation (such as refueling), never park a vehicle carrying Division 1.1, 1.2, or 1.3 explosives within 300 feet of a bridge, tunnel, or building. Never park such a vehicle within five feet of the traveled portion of the road.

Strong winds can make it difficult to keep a vehicle in its proper lane. Strong wind can be a particular problem when a vehicle is being driven out of a tunnel.

It is illegal to transport liquids or gases in a leaking tank. If you do drive a leaking tank, you may be liable for the costs of cleaning up the spilled material.

Ice becomes wet when the weather is just warm enough to melt the ice slightly. Wet ice is much more slippery than ice that is not wet.