Under what conditions are retarders typically used?

Retarders are typically utilized when going down long hills primarily due to their ability to help control the speed of the vehicle without relying solely on the brakes. When traversing long, steep descents, standard brakes can overheat or wear out due to continuous use, leading to diminished braking performance and potential brake failure. Retarders work by offering a supplemental braking force, often utilizing engine braking or electronic devices to manage vehicle speed effectively while maintaining control and safety. This is particularly crucial in emergency responses where maintaining a safe speed is essential to ensure both the safety of the ambulance occupants and the public, as well as the timely delivery of emergency care.

The other options refer to scenarios where the use of retarders is either unnecessary or potentially counterproductive. For instance, high-speed driving typically requires acceleration rather than deceleration, while heavy traffic places emphasis on maneuverability and responsiveness rather than ongoing deceleration. Sharp turns call for precise steering control rather than heavy braking, which could destabilize the vehicle.