The oil palm railways of North Sumatra share a common heritage with the sugar railways of Java, but there are significant differences. The Javanese railways were established around the turn of the century and much of the locomotive stock dates from that time. The narrow gauge industrial lines in North Sumatra were laid down in the 1920s and the initial locomotive stock was representative of the trends at that time. Also, when the sugar industry faced a slump in the early 1930s, many locomotives were sent from Java to Sumatra.

With the Dutch locomotive industry still marginal, several German manufacturers were represented but Orenstein and Koppel (OK), who were the leading supplier to the sugar railways, were the natural 'market leaders'. However, whereas in Java, the dominant type was always the Klien Lindner axled 0-8-0T, in Sumatra it was the earlier Mallet 0-4-4-0T which found favour. Later, when very powerful locomotives were required Luttermöller 0-10-0s were bought from OK.

By the time that the railways were established and additional locomotives were required, DuCroo and Brauns (DB) in Holland were in a position to satisfy most of their needs. Like OK they built 0-8-0T and Mallet 0-4-4-0T. The former seemed not to have been a great success, by the time that early visitors came to North Sumatra in the early 1970s, all had been set aside and those few remaining were rusty hulks. On the other hand, the Mallets seem to have been an outstandingly successful design, comfortably outlasting their OK counterparts and becoming the dominant motive power in the closing years.

Later, DB produced some rugged and powerful 0-6-0 both with and without tanks which were another successful design. Among the 'standard' locos there were a number of other designs used and these are discussed in the section which follows.