 Disputes between VR and NSWGR during the design and construction phase of the passenger carriages had led to several compromises, including the ability to fit bogies of the preferred types of both railways.Due to the insistence of manufacturer Commonwealth Engineering, stainless steel was eventually selected as the primary material, despite the initial reticence of the railways, who wished to use their own existing carriage designs.Among the vaunted benefits of stainless steel construction was its superior crashworthiness, a benefit that was maximised by late design changes made to improve the energy absorbing capacity of the draw gear between carriages.