When should a retarding device be used while driving a truck?

Using a retarding device, such as an engine brake or Jake brake, should primarily be applied on steep downhill grades. These devices are specifically designed to help control the speed of the vehicle by using the engine's compression to slow down, which can be especially beneficial on steep slopes. This practice helps in preventing brake overheating and reduces wear on the brake system, ultimately enhancing safety.

While retarding devices provide significant control in specific conditions like steep grades, they may not be suitable for everyday driving in normal conditions due to potential traction loss, especially on slippery or uneven surfaces. Utilizing them on snow-covered or wet roads can lead to hazardous situations where the vehicle may lose grip. Therefore, the most appropriate scenario for employing a retarding device is while navigating downhill inclines, where maintaining a controlled speed is crucial.