Revision question · The road

What is the purpose of a correctly adjusted roof air deflector between a lorry cab and a taller body or trailer?

Revision material from the imported DVSA bank includes source-checked Lanekind learning corrections. These corrections are not newly issued official examination questions, and practice does not reproduce a live test paper.

Answer options

To increase the load’s permitted height

To improve airflow and reduce aerodynamic drag

To replace load restraints

To remove the need to check crosswinds

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To improve airflow and reduce aerodynamic dragThis was the right answer

The deflector guides airflow between the cab and the taller body or trailer. Set it for the actual combination as the manufacturer instructs. Savings depend on its adjustment, body shape and conditions; a headwind is not a universal test of effectiveness.

Reviewed reading for this question

Guide airflow between cab and trailerReviewed guidance summary · The revised learning question tests the actual aerodynamic function.

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