The class 001 designates six-axle diesel-electric locomotives originally fitted with 1,200hp Crossley two-stroke diesels. They were intended for passenger and freight service and were built by Metropolitan-Vickers in Manchester. The low reliability of the Crossley engines meant that from 1968 they were rebuilt to engines of the EMD 645 type. These also worked on the two-stroke principle and initially produced 1,650 hp. Since the propulsion electronics and the cooling system were stressed with this power, the power was soon reduced to 1,325 hp. The 60 locomotives provided valuable services until they were replaced by new class 201s in 1994.

To replace steam locomotives in freight traffic, the NS had the series 2200 built between 1955 and 1958. Baldwin and Westinghouse were involved in the development. They had only a cab at one end and a narrow engine compartment with running boards. The mechanical part was manufactured partly by Allan in the Netherlands and partly by Schneider in France, while the electrical part came from Heemaf.

Some of them were also used for passenger trains, with a steam heat car being used in colder weather. Some locomotives were even equipped for sandwich operation. Due to the decline in freight traffic, the first ones were retired between 1972 and 1974, and many only disappeared from 1985 onwards. The last ones were retired in 2003.