When Uff investigated Southall, the concept of crumple zones in rolling stock was slowly becoming established. He wrote: "A particular design feature which has proved controversial is the introduction of 'crumple zones', as energy-absorbing measures at the end of coaches. This was opposed by some who considered that it represented a new hazard in view of the possibility of passengers being located within these zones." British Rail designed and built its HSTs before crumple zones became common.