Michigan CDL Permit Test - Combination

Correctly following the steps to couple and uncouple trailers is vital to safely operating a combination vehicle. After connecting the air lines to the trailer while coupling, you should supply air to the trailer.

To help prevent a rig from rolling over, you should keep the weight of the cargo as close to the ground as possible when loading. You should also drive slowly around turns.

When connecting a converter dolly to a second or third trailer, the trailer height should correct. It should be slightly lower than the center of the fifth wheel.

Combination vehicles need more space on the road than other commercial vehicles because they are longer and need more space to turn and stop. It is especially important to properly manage space when you are operating a combination vehicle.

Older trailers do not have spring brakes. This means that if the air supply in an older trailer's air tank has leaked away, there will be no working brakes connected to the trailer and its wheels will turn freely.

Railroad-highway crossings may be difficult to cross when pulling a trailer with a low underneath clearance. In particular, both low-slung units and single-axle tractors pulling long trailers are especially challenging to drive over raised crossings.

When making a turn, be sure to steer gently and smoothly. Making a quick turn while pulling trailers is dangerous and can increase the risk of the last trailer rolling over.