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.

The PeoplePanel™ side protection signage (Cyclist & Pedestrian

Understanding Side Underrun Protection - Power Torque

Semi-trailer truck - Wikipedia

Semi-trailer truck - Wikiwand

Side underrun protection guidelines updated

DVSA publishes new guidance on fitting vehicle side guards – Moving On

Livestock Transportation Use Fence and Side Panel Cargo Truck Semi Trailers - China Fence Cargo Trailer, Side Panel Truck Trailers

Understanding Side Underrun Protection - Power Torque

Thompsons HD (Side) Under-Run protection Kit *V2 Galvanised