However, with the start of dieselisation in 1950s and speeding up of electrification from 1960s, the face of railways started changing. Electric locomotives, compared to steam locomotives, required more items that were sophisticated and had to be purchased. It was mainly with dieselisation and electrification, that the purchase function of railways started evolving though other changing areas, e.g. signaling, production of coaches, track laying, and maintenance activity. Apart from more number of purchase items, the issues like quality and reliability of items and the firms who were supplying them also became relevant as diesel and electric locomotives required sophisticated items for which credentials and capabilities of vendors needed to be pre-assessed. Activity of approval and registration of firms thus started. As the railway system was expanding, the funds became scarce and there was an urgent need to keep inventories at optimum levels so that capital could be used elsewhere, making inventory control important. Similarly the scrap sales function also became more and more important over the years.