Inexperienced drivers often believe that a strong truck with a trailer hitch is all that's needed for safe hauling. A good truck with the right hitch is certainly very important, but it has nothing to do with pulling that trailer safely.
Driver knowledge and experience must be added before a trailer can be pulled safely. The driver must understand the pulling characteristics of his particular truck. Slight differences between vehicles can make a huge difference in the performance of the truck/trailer combination on the road.
Same could be different
Individual trailers, and even identical trailers, often pull very different when moving down the road. Length, loaded weight, balance, and tongue weight of the trailer are other important factors in how well it pulls (and stops) at road speed. Beyond that, the trailer's lights, brakes, load security, and flagging (if needed) are critical issues every driver must check before hitting the road.
Trailer lights and hook up (including the safety pin) must be checked each time the driver makes a stop. Walk around the trailer to check the load and tie downs before heading to the next destination.
Tongue weight is a critical safety issue. If there is too much weight, the front of the truck lifts slightly, often affecting the performance of the brakes in an emergency. If there is too little weight, the trailer has the tendency to sway excessively in turns and during stops. In an emergency, rear truck tires can lose traction and jackknife.
Most trailers should have a tongue weight of around 60% of the total trailer weight. The trailer can normally be balanced properly by shifting a heavy item forward or backward before tying everything down.
Trailer brakes must be in good working condition and be properly adjusted. Check to make certain that they are operating properly before pulling into traffic by depressing the manual lever on the brake controller. Adjust trailer brakes for each trailer you pull, every time you use it.
When stepping on the brake pedal, you should be able to feel the trailer brakes apply, but they should not jerk the truck. If a problem develops with the adjustment process, a mechanic will be able to help you master the skill.
The condition of the truck is also important. Pulling a trailer puts a heavy load on the vehicle, and if it is not running properly, don't risk breaking down in traffic. Mechanics prefer to work on the truck at a lot or in their shop rather than in traffic along a congested highway.
Driver experience is very important. Learn to drive the trailer, not the truck. In other words, drive so the trailer maintains proper road position in curves and turns, and most importantly, stays in the proper lane. Longer trailers make this skill extremely important.