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C1Difficulty 3/5

A heavy lorry has a working electric retarder. On a steep descent with adequate grip and use permitted by the manufacturer, how should it be used to reduce sustained demand on the service brakes?

Correct answer

Use the retarder and engine braking with an appropriate gear, applying the service brakes when needed.

Use the retarder with an appropriate gear and engine braking according to vehicle instructions; apply the service brakes whenever needed to control speed safely. Auxiliary braking reduces sustained demand and heating of the service brakes but does not replace them in every situation. Adapt power and operation to load, gradient, speed, grip and system design.

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All options

  • Use the retarder and engine braking with an appropriate gear, applying the service brakes when needed.

  • Use only the service brakes continuously and ignore the available retarder.

  • Use the retarder as a complete substitute for service brakes in every situation.

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