The easiest way to spot a trailer skid is to use your mirrors. Any time you brake hard, check your mirrors to ensure that your trailer is still in its proper position.

The trailer hand valve works the trailer brakes but should only be used when testing them. Using it while driving could create 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.

The service air line carries air and is controlled by either the foot brake or trailer hand brake. The service air line is attached to relay valves, which allow the trailer brakes to be applied quickly.

You can tell that your vehicle is equipped with an Anti-Lock Braking System (ABS) if it has a yellow ABS malfunction lamp on the instrument panel.

Retarders are mechanisms in some vehicles that help slow a vehicle and reduce the need for braking. However, using a retarder may cause wheels to skid when they have poor traction. Turn off retarders when traveling under wet, snowy, or icy conditions.

To avoid becoming an aggressive driver, begin a trip with realistic expectations of how long the trip will take, allowing extra time for traffic delays. Do not tailgate other vehicles. To avoid upsetting other drivers, do not drive slowly in the left lane and do not gesture at the drivers (even in seemingly minor ways, like shaking your head).

If confronted by an aggressive driver, the most important thing to do is try to get out of their way. Avoid making eye contact with the driver and do not let yourself be provoked by gestures. Do not try to challenge aggressive drivers by speeding up.

In a double or triple, the more heavily-loaded trailer should be immediately behind the tractor.

At dawn or dusk, and in snowy or rainy conditions, you should turn on your headlights to make it easier for other road users to see your vehicle.

The earliest and best way to recognize the beginnings of a trailer skid is by seeing the trailer veer off-course in your mirrors.

Wheels or rims with welding repairs are not safe.

Due to the "crack-the-whip" effect caused by rearward amplification, changing lanes too quickly in a combination vehicle can result in a rollover.

Stay aware of upcoming obstacles and hazards by consistently watching the road at least 12 to 15 seconds ahead of your vehicle. When traveling at highway speeds, this is equivalent to about a quarter of a mile.

If a pre-trip inspection reveals anything unsafe about your vehicle, you must get it repaired. It is illegal to operate an unsafe vehicle.

Anti-Lock Braking System (ABS) malfunction lamps are usually yellow. Even if the ABS isn't working properly, a driver will still have access to the vehicle's usual braking functions.

Driving at excessive speeds is a major cause of fatal crashes. Never drive above the posted maximum speed limit and adjust your speed to fit conditions.

Before starting down a hill, be sure to switch into a low gear. Gravity will increase your vehicle's speed as you travel downhill.

A trailer tends to swing around, potentially resulting in a trailer jackknife, if its wheels lock up.

Brakes can get out of adjustment quickly, especially if they are used to the point of overheating. Brake adjustment should be checked frequently.

The "crack-the-whip" effect makes the last trailer in a combination the most likely to turn over. Be especially careful when operating a double or triple combination vehicle around a turn or corner.