Page 2 General Knowledge Test Study Guide for the CDL

Other Safety Precautions

Backing Up the Trailer

Try to avoid backing up your trailer whenever possible. If you must back it up, back to the driver’s side (left) for optimum visibility. Unlike in other shorter vehicles, when you back up a trailer, you turn the wheel in the opposite direction of where you want to go. Drive slowly and use your mirrors. If you start to head in a direction you do not want to go, turn the steering wheel toward that direction to correct the drift.

Seeing While You Drive

Because of the length of commercial tractor-trailers, every action you make takes extra time and consideration. While driving, try and look 12–15 seconds ahead of you to make sure you have enough time to react to topography changes, traffic, and difficult road conditions. Use your mirrors, but do not look at them for too long. Your main focus should always be what is coming up ahead.


Use your turn signals to indicate to other drivers what you intend to do. Put them on well before you make a turn and do not turn them off until you have completed it. If you see a hazard ahead such as debris in the road, flash your brake lights. Because of your size, the drivers behind you may not be able to see very far ahead of them, and flashing your brake lights helps alert them to slow down. If you are passing a bicyclist or pedestrian and it is safe and legal to do so, honk your horn. They might not hear or see you so this alerts them of your presence. If you ever have to stop on the side of the road, put out your reflective triangles within 10 minutes of the stop.

Managing Space

Because your vehicle is much bigger than many others on the road, you need more space in front of you for stopping. A good rule of thumb is that you need 1 second for every 10 feet of vehicle length at speeds under 40 miles per hour. If you are traveling faster than 40 miles per hour, add an extra second. For example, a 50-foot trailer driving 60 miles per hour would need 6 seconds to stop (5 seconds for vehicle length plus 1 second for going over 40 miles per hour). Of course, if road conditions are slippery or you are on a hill you may need additional time to stop, so adjust your speed accordingly.


If you are turning left, you should have reached the intersection before beginning your turn. When there is more than one turn lane, always take the outside-right lane, instead of the inside-left lane, because you may need to swing right to complete your turn. If you were on the left lane, swinging right would mean you could potentially end up hitting the driver next to you. If you are turning right and need to swing wide, try and keep the rear of the vehicle close to the curb so other drivers do not try to pass you on the right.

Difficult Road Conditions

Knowing what to do in different types of inclement weather or challenging topography can greatly increase your chances of a safe trip. Be aware that even on hot, sunny days, tar on the roads can rise to the surface, making the road slippery. If you cannot avoid driving in fog, drive cautiously, turn on your low beams, and be prepared to stop. If you are driving in a mountainous area, shift to low gear before descending down a hill. Drive slowly enough that you do not constantly have to use your brakes. Using brakes too often causes them to get hot and may result in brake failure. If you are driving through a large puddle and your brakes get wet, put the transmission in low gear and gently put pressure on the brakes. When you are out of the water, continue to put light pressure on the brakes to heat them up and dry them out.