Illinois CDL Practice Exam

Off-tracking refers to the phenomenon where a vehicle, especially a combination vehicle like a truck and trailer, does not follow the exact path as its front wheels when making a turn. This occurs because the rear wheels of the trailer take a wider trajectory than the front wheels of the tractor, causing the rear wheels to track differently from the front wheels.

This is particularly important for drivers to understand, as it can result in the back of the trailer swinging outward, possibly colliding with obstacles or other vehicles during turns. Recognizing off-tracking helps drivers maintain better control of their vehicles, particularly in tight turns or when navigating through confined spaces.

The other choices do not accurately define off-tracking. Driving off the designated path on highways refers to a different scenario and does not specifically involve the movement characteristics of different vehicle parts. The movement of a trailer when a tractor starts moving doesn't describe the comparative path of the wheels in a turning scenario. Finally, reducing fuel usage by optimizing driving routes pertains to efficiency in driving rather than the technical maneuvers of vehicle movement.