This description was taken from Australian Trucking Association – Side Underrun Protection:

This Advisory Procedure is published by the Australian Trucking Association Ltd (ATA) to assist the road transport industry improve the technical understanding of Side Underrun Protection Systems and the application of Side Underrun protection to heavy duty trucks and heavy trailers. The Advisory Procedure has been drafted to apply to a generalized range of typical Australian transport industry trucks and trailers and provides guidance for “deemed” compliance in accordance with the requirements as set-out in UN-ECE regulation R73. It is not, nor is it intended to be, complete or without exceptions.