When inspecting your vehicle's engine, check the belts for tightness and excessive wear. The amount of "give" that is safe for each belt in a given engine will vary, so learn what is appropriate for your vehicle.

Because the weight of cargo gives them a higher center of gravity, fully-loaded rigs are 10 times more likely to roll over in a crash than empty rigs.

Always apply the parking brake when leaving your vehicle.

When using a fire extinguisher, you should stand as far away from the fire as possible. Aim the extinguisher at the base of the fire, not at the flames. If you are not sure which kind of extinguisher should be used on a fire, particularly a hazardous materials fire, you should wait for the firefighters to arrive and allow them to extinguish it.

The air compressor of an air brake system is connected to the engine through gears or a v-belt. The compressor may be air-cooled or cooled by the engine cooling system.

The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.

If your vehicle "pulls" to one side when braking, you may have brake trouble. If there is an issue with your brakes, you should fix the issue before driving. Operating an unsafe vehicle is against federal and state laws.

Before driving during the winter, make sure to check your defrosting and heating equipment, coolant and antifreeze levels, wipers and washers, tire tread, tire chains, lights, reflectors, and exhaust system. Clear ice and snow from all windows, mirrors, hand holds, steps, deck plates, and radiator shutters. Make sure the winterfront is not closed too tightly.

To make a normal stop in a vehicle with air brakes, push the brake pedal down. The harder the pedal is pressed, the more air pressure is released.

If you must drive slowly, you should use your emergency flashers to warn other drivers. Be sure that the use of emergency flashers is permitted by local laws.

If you are not sure which kind of extinguisher should be used on a fire in your vehicle, particularly a hazardous materials fire, you should wait for the firefighters to arrive and allow them to extinguish it.

If you experience an engine fire, you should turn off the engine as soon as safely possible. Avoid opening the vehicle's hood when extinguishing the fire.

If your CMV gets stuck on railroad tracks, you should immediately leave the vehicle and get away from the tracks. Check the signposts or signal housing at the crossing for emergency contact information and call 911, or another appropriate emergency number.

If you choose to use a mobile phone while operating a CMV, you may only use a hands-free mobile phone that is located close to you. However, even a hands-free mobile phone can be a dangerous distraction while driving. Make sure you are aware of all cell phone laws in the state in which you are driving.

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.

In general, the parts of the service air line are coded blue and the parts of the emergency air line are coded red.

Before driving, you should always verify that your service brakes are in good working order. Testing the brakes before a trip allows you to locate any problems before you need to brake while on the road.

A broken exhaust system can allow poisonous fumes to enter a vehicle's cab or sleeper berth. Be sure to regularly check your exhaust system for defects.

Be sure to test the trailer emergency brakes before beginning a trip. After ensuring that the trailer rolls freely, you can test the emergency brakes by pulling out the trailer air supply control, or placing it in the "emergency" position. Pull forward slightly with the tractor and make sure the trailer does not move.

Watch the gauges in your vehicle before starting a trip. After starting your vehicle's engine, the coolant temperature should begin a gradual rise to the normal operating range.