What does side underrun protection do on trucks and trailers?

If you see bars down the side of a truck or trailer between the axles, this is side underrun protection and it's designed to stop cyclists, motorcyclists low vehicles and other road users falling, sliding or driving underneath the truck or trailer and being run over by the rear wheels.

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What does side underrun protection do on trucks and trailers?

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What is side underrun protection on a truck or trailer?

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