The suspension system keeps a vehicle's axles in place. Damaged suspension parts, such as leaking shock absorbers, may be potentially dangerous defects on a vehicle.

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.

Always speed up smoothly and gradually so that your vehicle does not jerk. Rough acceleration can cause mechanical damage.

A steering wheel should have no more than 10 degrees of play. This is equal to about two inches of movement at the rim of a 20-inch wheel. If there is more play than this, it may be difficult to steer.

To avoid being blinded by the lights of oncoming vehicles, you can glance to the right side of the road until the vehicle has passed.

If confronted by an aggressive driver, don't let yourself be provoked by their actions or angry gestures. Do not risk provoking the other driver by making eye contact. Get out of their way if you can do so safely.

Hazardous materials placards must be placed on a vehicle at least three inches away from any other markings and must positioned so that the words or numbers are level and read from left to right.

Before a trip, be sure to inspect all couplings. There should be no space between the upper and lower fifth wheel.

Pre-trip inspections should be conducted in the same way every time. This will reinforce the steps, making it less likely that you will forget to inspect something important.

If a cargo leak develops while you are carrying hazardous materials, do not continue driving any farther than safety requires. The farther you drive, the larger the contaminated area will become. You should park the vehicle, secure the area, and stay with the vehicle while sending someone else to get help.

The easiest way to become aware that your trailer has begun to jackknife is to observe it in your mirrors. Checking your trailer in your mirrors will also allow you to spot any skidding at the earliest possible moment.

It is critical that an engine have sufficient oil pressure. The engine can be destroyed rapidly if run without oil.

The leading cause of injury and death in roadway work zones is excessive speed by passing drivers. Lower your speed when driving through a work zone.

If the weight of your vehicle prevents you from matching the speed of surrounding traffic, you should stay in the right lane, if possible.

When inspecting your vehicle, you should check the wiper blades for damage, stiff rubber, and proper securement. Clean the blades if they are dirty.

To avoid becoming fatigued on a long trip, you should take a break after every 100 miles or two hours of driving. Driving through the night, or during any other time when you would normally be asleep, raises the danger of fatigue.

You should tap your brakes and flash your brake lights to warn other drivers any time you plan to slow or stop where other drivers may not expect you to do so. Use this technique when stopping on the road to unload cargo or passengers.

After a trip, you may be required to perform an inspection and file a report on each vehicle that you've driven.

During a pre-trip inspection, you should activate your lights, then get out of the vehicle to look at them.

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

Trailers equipped with Anti-Lock Braking Systems (ABS) are equipped on the left rear with a yellow malfunction lamp. If the malfunction lamp stays on after the engine has been started, the ABS is malfunctioning.

At times when visibility is low, you should turn your headlights on to the low beam setting. If you are having a difficult time seeing others, they are probably having a difficult time seeing you.

Tractors without semi-trailers are referred to as "bobtail tractors." Bobtail tractors are difficult to operate and drivers must exercise caution.

An Anti-Lock Braking System (ABS) helps prevent wheel lockup during hard braking. If ABS detects impending lockup, it reduces braking pressure to a safe level.

Black ice is a thin layer of ice that is clear enough for the road surface to be seen through it. A road covered in black ice may look like it is merely wet. You should be very careful when temperatures are below freezing and the road looks wet.

Eating while driving can be a dangerous distraction to the driver both because it diverts their attention away from the task at hand and requires them to remove a hand from the steering wheel.

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.

Black ice is a thin layer of ice that is clear enough for the road surface to be seen through it. A road covered in black ice may look like it is merely wet. You should be very careful when temperatures are below freezing and the road looks wet.

Wheels or rims with welding repairs are never safe to use.

On a steep downgrade, you must use the engine's braking effect as your primary method of speed control. Be sure to decelerate and downshift appropriately before beginning to drive down the hill.