You should test the tractor protection valve by allowing the air supply to properly charge, turning off the engine, then releasing air from the system by pressing the brake pedal several times. The tractor protection valve should move into its emergency position when psi drops to an unsafe level.

When applying for an original or renewed HazMat endorsement, you must undergo a federal security threat assessment done by the Transportation Security Administration (TSA).

One way to know when it is time to shift gears is to learn your vehicle's operating rpm range. You should shift up when your engine reaches the top of that range. You can also learn which speeds each gear is good for and shift up based on your speedometer.

Tanks require extra care when being driven because they tend to have high centers of gravity. Drivers operating tank vehicles should be particularly careful when taking curves and corners.

Bridges tend to freeze before other parts of the road surface. You should be especially careful on bridges when temperatures are near the freezing point.

A tank vehicle transporting liquids is less stable than other vehicles and may be prone to roll over or skid if not operated in a safe manner. If you must make a quick stop to avoid an accident while transporting liquid cargo, it may be a good idea to use the controlled braking method.

During a trip, you should regularly make checks to ensure that your vehicle is operating properly. Check the instrument panel and gauges; look at your mirrors; and examine the tires, cargo, and lights. Use all of your senses and be alert for anything that could be an early indication of trouble.

Backing a truck is always dangerous because the driver may not be able to see everything behind them. CMV operators should avoid backing whenever possible.

Ice cream trucks can create hazardous conditions for other drivers because they attract children. Children often do not notice or pay attention to other vehicles on the roadway when running to or from ice cream trucks.

Using a hand-held mobile telephone while operating a CMV is both illegal and dangerous.

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 must drive so slowly that you will impede the flow of traffic, you should turn on your four-way flashers to alert drivers behind you (as long as local laws allow the use of flashers).

Combination vehicles are usually heavier and longer than single combination vehicles. Operating a combination vehicle requires a higher level of driving skill than operating a single commercial vehicle.

When connecting a converter dolly to a second or third trailer, the trailer height should correct. It should be slightly lower than the center of the fifth wheel.

If you must drive in reverse, you should first walk around your vehicle to look at the path of travel and check for obstacles. Because mirrors have blind spots, you cannot rely exclusively on them. It is recommended to use a helper whenever possible.

A person attending a parked placarded vehicle must be either awake inside the vehicle or they must be within 100 feet of it. If not inside the vehicle itself, the person must have a clear view of the vehicle. The person attending may not be inside the sleeper berth.

Baffled tanks contain holed bulkheads that allow liquid to flow through the tank. This helps to inhibit front-to-back surge, but does not prevent side-to-side surge.

If transporting any amount of chlorine, a driver must always stop at a railroad crossing 15 to 50 feet from the nearest track, regardless of the presence of a train.

While driving, you should watch your vehicle's gauges for signs of trouble. Be sure to inspect your gauges before beginning a trip to ensure that they are in proper working order.

Liquids expand as they get warmer and drivers must allow extra space in a tank to accommodate this expansion. Different liquids expand to different degrees, so drivers must be aware of the outage requirements of the specific load they are carrying.