Gross Combination Weight (GCW) is the total weight of a powered unit, its trailer(s), and the cargo being carried.

For safe driving, it is essential that you maintain cushions of space on all sides of your vehicle. This helps to ensure that you will have time to take appropriate action if a problem arises.

If you begin to feel sleepy while driving, the only safe response is to stop driving and get some sleep. Attempting to fight off exhaustion is dangerous and a major cause of fatal crashes. Stimulants are not a safe solution because they may help keep you awake but will not make you more alert. Once stimulants wear off, you will be even more tired than you were originally.

Brakes are particularly prone to getting out of adjustment if they are hot. Be sure to routinely check the adjustment of your brakes. For a vehicle to be safely controlled, all brakes must be properly functioning and adjusted.

It is important to know the maximum air loss rate that is safe for your specific vehicle. A triple combination should have a leakage rate no higher than 6 psi in a minute during an applied leakage test.

If water and compressor oil are left to build up in an air brake system, the system can be damaged. Air storage tanks are equipped with drains to allow this accumulation to be removed. Manually controlled drains should be operated at the end of each day of driving.

Rollovers occur when drivers turn or change lanes too quickly.

If there is enough water on the road, hydroplaning can occur at speeds as low as 30 mph. It is most likely if the tires' air pressure is too low or if tires' tread is worn.

Mirror adjustment should be checked prior to the start of each trip. Any attached trailer should be straight while mirrors are being adjusted.

To alert drivers behind you that you plan to slow down, tap your brake pedal lightly a few times to make the brake lights flash.

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.

When turning on your vehicle's engine, the lights on the dash should come on and then turn off. If the ABS malfunction light stays on, the system is not working properly. In the case of a truck with a trailer, if the yellow light on the left rear of the trailer stays on once the engine has been started, the system is not working properly.

While regular mirror checks should be part of your normal scanning routine, be especially sure to check your mirrors when changing lanes.

The securement of cargo must be checked before beginning a trip, within the first 50 miles of a trip, and then again every three hours or 150 miles.

Driving at night is more dangerous than driving during the day because hazards become more difficult to see in the dark.

The total stopping distance for vehicles equipped with air brakes is made up of four factors: perception distance, reaction distance, brake lag distance, and braking distance. When braking at a speed of 55 mph while driving on dry pavement, the brake lag can add around 32 feet to a vehicle's total stopping distance.

When performing a static leakage test on a triple combination vehicle with air brakes, the leakage rate should be no more than 5 psi in one minute. If air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

Vehicles with ABS have yellow malfunction lamps to alert drivers when the braking systems are not working. Be sure you know where the malfunction lamp on your vehicle is before beginning a trip.

A vehicle with air brakes must be equipped with a low air pressure warning signal. If the warning signal goes off while a vehicle is being driven, the driver should bring the vehicle to a complete stop and have the system repaired.

The adjustment of your mirrors should be checked prior to the start of all trips. Adjust your mirrors as needed.