The trailer hand valve (also referred to as the trolley valve or Johnson bar) is a mechanism that works the trailer brakes. It should only be used to test the brakes. Using it while the vehicle is being driven could cause a skid. Never use the trailer hand valve while parking because doing so may release the air pressure from the braking system, releasing the brakes that are holding the vehicle in place.

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.

When backing with a trailer, you should pull up to reposition your vehicle as needed.

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.

Factors that can affect stopping distance include your vehicle's speed, its weight, and the traction provided by the road surface.

Texting while driving a CMV is prohibited. "Texting" is defined as manually entering text into, or reading text from, an electronic device.

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.

If a vehicle is top-heavy, it is more likely to roll over. The weight of cargo should be positioned as low in a trailer as possible to minimize this risk.

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.

Surge results from the movement of liquid in tanks that are partially filled.

Explosives are placed in hazardous materials Class 1.

When inspecting an exhaust system, you should verify that parts of the system are not loose, broken, or missing. The system's parts must be properly mounted and should not be rubbing against moving parts of the vehicle.

A steering wheel should be held firmly with both hands, positioned on opposite sides of the wheel.

If you are transporting radioactive material and believe there is a leak or broken package in your cargo, you should tell your dispatcher or supervisor as quickly as possible. Do not touch or inhale the material. Do not use the vehicle until it has been cleaned or checked with a survey meter.

Controlled braking is the method of applying a vehicle's brakes as hard as possible without locking the wheels. A driver should keep steering wheel movements very small if braking while using this method.

The most important reason to inspect your vehicle before a trip is to ensure the safety of yourself and others on the road.

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.

You should never exceed the speed shown on a "Maximum Safe Speed" sign.

Tires on the same vehicle should all be equally sized. Ensure your tires are not mismatched when inspecting your vehicle.

Low beam headlights allow you to see about 250 feet ahead of your vehicle. When driving at night, adjust your speed so that you will be able to stop in the distance illuminated by your headlights.