Air brake system tanks must contain drain valves. These valves are used to drain accumulated oil and water from the tanks and may be either manually or automatically operated.

Fatigue and lack of alertness are major hazards when driving at night. Most people are the least alert at night, especially after midnight.

If you are attaching a second trailer to a combination but the trailer is not equipped with spring brakes, you can set the trailer emergency brakes. You can do this by connecting the first and second trailers' emergency lines, charging the air tank, then disconnecting the emergency lines. This should set the emergency brakes, as long as the slack adjusters are properly adjusted.

Your vehicle's engine may need to be running in order for you to check the level of its automatic transmission fluid.

To avoid becoming an aggressive driver, begin a trip with realistic expectations of how long the trip will take, allowing extra time for traffic delays. Do not tailgate other vehicles. To avoid upsetting other drivers, do not drive slowly in the left lane and do not gesture at the drivers (even in seemingly minor ways, like shaking your head).

When driving in reverse, it is always recommended that a driver backs their vehicle toward its left side. This will allow the driver the best possible view of the rear of their vehicle.

Roads are especially slippery when it first begins to rain. Rain water initially mixes with oil and grease on the road to form a slippery film. As the rain continues, this mixture will eventually wash away.

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

Shut-off valves are used in air supply lines to control the passage of air from one trailer to another. The rear shut-off valve should always be closed to prevent air from leaving the braking system.

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.

A hot, poorly-ventilated area can make a person sleepy. Opening a window, opening a vent, or using the air conditioning can help keep the cab cool and reduce the risk of fatigue.

Large combination vehicles take longer to stop when they are empty than when they are loaded. The decreased weight causes a vehicle's wheels to have decreased traction on the surface of the road.

You should never assume that you will hear an approaching train. The train operator may fail to sound the horn, or the use of a train's horn may be prohibited in a specific area. Even if the train does sound its horn, noise from inside your own vehicle may prevent you from hearing the train until it is dangerously close.

If the weight of your vehicle prevents you from matching the speed of surrounding traffic, you should stay in the right lane, if possible.

When starting a trip, be sure that all shut-off valves are in the open position, except for the last valves on the rear trailer. It is important that air reaches the brakes on all trailers and that the air is not able to escape from the back of the vehicle.

It is essential that your low pressure warning light function properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.

A dual air brake system has two separate air brake systems that use a single set of brake controls. One system typically operates the regular brakes on the rear axle or axles. The other system operates the regular brakes on the front axle.

During a trip, you should regularly check the gauge and instrument panels, mirrors, tires, cargo, and lights for signs of trouble.

Convex mirrors are also known as "fisheye", "spot", or "bug-eye" mirrors.

Never unlock the pintle hook with the dolly still under the rear trailer. This could cause the dolly tow bar to fly up, possibly causing serious injury.