Driving while fatigued is dangerous. Warning signs of fatigue include difficulty focusing; repeated yawning or rubbing of the eyes; daydreaming or wandering thoughts; and drifting out of your lane.

Rust around wheel nuts may mean that they are loose. Check the tightness of the nuts if you see any rust in the area.

While driving, you should continually scan the road to spot potential hazards in advance. Make emergency plans for how to deal with the hazards if they become dangerous.

You must have a commercial driver license with a hazardous materials endorsement before driving a vehicle of any size that is used to transport hazardous materials, even if the vehicle is not transporting hazardous materials at the time of operation.

Air expands as it gets warmer, so the air pressure in your tires could reach dangerously high levels while being used in very hot weather. If this happens, stop and let your tires cool. Do not let air out of the tires, as this could result in the pressure dropping to an unsafe level once the tires cool down.

If the words "Inhalation Hazard" appear on a package or its shipping paper, the "Poison Inhalation Hazard" or "Poison Gas" placards, as appropriate, must be displayed.

Because liquids expand when their temperatures increase, some space must be left in a tank to accommodate the expansion. This space is referred to as "outage." The amount of required outage is different for different liquids.

Combination vehicles need more space on the road than other commercial vehicles because they are longer and need more space to turn and stop. It is especially important to properly manage space when you are operating a combination vehicle.

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

Trailers and converter dollies built on or after March 1, 1998 are required to have Anti-Lock Braking Systems (ABS). This will be indicated by the presence of a yellow malfunction lamp. You can determine if older trailers have ABS by checking under the trailers for ECU and wheel speed sensor wires coming from the back of the brakes.

Being under stress can lead to aggressive driving, which is dangerous. Playing calming music can help you become more relaxed if you are feeling stressed while driving.

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.

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.

In places where water collects on the road, it is possible for a vehicle to hydroplane. Low tire pressure or worn tire tread makes this more likely to happen. If there is enough water on a road surface, hydroplaning can occur at speeds as low as 30 mph.

Radioactive materials are categorized as Class 7 hazardous materials.

When inspecting any style of tank, the most important thing for a driver to check for is leaks. Transporting any type of gas or liquid in a leaking tank is illegal.

The average driver has a reaction time of between three-quarters of a second and one second.

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.

If you are approaching a traffic light that has been green for a long time, there is a good chance that it will turn yellow before you reach it. Start slowing down and be ready to stop.

For safe driving, it is essential that you are aware of what is happening on all sides of your vehicle. In addition to watching the road ahead, you should frequently check your mirrors to monitor the road to the sides and to the rear of your vehicle.