When should you not use speed control on a truck with multiple trailers?

Using speed control on a truck with multiple trailers should be avoided on slippery or steep roads due to the potential for loss of control. When navigating such conditions, the additional weight and length of the trailers can make it more challenging to respond to changes in traction and incline. Slippery surfaces, such as those that are wet, icy, or snowy, require a driver to maintain greater control over their speed and braking to prevent skidding or jackknifing.

On steep roads, the dynamics of a multiple trailer setup change significantly. The tendency for trailers to push against the towing vehicle can increase on declines, requiring careful management of speed through manual throttle and brake control rather than relying on a speed control system that may not adjust as effectively. Maintaining direct control allows the driver to react to the terrain and road conditions in real-time, enhancing safety and stability.