What is the primary function of retarders in a vehicle?

The primary function of retarders in a vehicle is to assist the braking system in slowing the vehicle. Retarders work by applying a resistance to the drive wheels, which helps to reduce the speed of the vehicle without solely relying on traditional brakes. This is particularly beneficial in large vehicles like trucks, where maintaining control and stability during braking is crucial.

Using a retarder reduces wear and tear on the vehicle’s brake components, enhances safety by providing additional braking power, and helps maintain a consistent speed on downhill grades. This means that, not only do retarders assist in slowing the vehicle effectively, they also contribute to the overall safety and efficiency of the operation of heavy vehicles.

The other options are not correct in this context, as retarders do not provide power to the engine, increase the vehicle’s speed, or primarily improve fuel efficiency. Their main purpose is to enhance braking capabilities, especially in demanding driving conditions.