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Incorrect!

Your lorry is stuck in snow. You use the diff-lock to move off. When should you switch the diff-lock off?

Only after selecting top gear
Once the engine has warmed up
You selected this answer
As soon as the vehicle is moving
Correct answer
As soon as the snow has cleared

DVSA theory test explanation

You must always disengage the diff-lock as soon as the vehicle is moving. The differential allows the rear wheels to revolve at different speeds, and this allows the vehicle to follow a curved path. Attempting to turn with the diff-lock engaged could result in the vehicle continuing straight on.

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