In June and July 1958, the South African Railways placed forty-five Class 1-DE General Electric type U12B diesel-electric locomotives in service.

When originally ordered, it had been the intention to use them on shunting and block-load transfers on the Reef and as part of the program to eliminate steam traction from the new Johannesburg station, but their success in this service prompted a change in utilisation policy.

In terms of speed and acceleration, they were superb and it didn't take long for the diesels to become a common sight on mainline working.

Their unqualified success played a large part in the eventual demise of SAR steam traction.

By the 1980s they were finally relegated to the shunting and pickup service that they were originally intended for when new, working on the Reef and at some other major centres.

[14] The locomotives were delivered in a livery that displayed the colours of the South African flag, white on the upper half and blue on the lower half, separated by an orange stripe on the sides and orange whiskers on the ends.

[6][15] The Class 31-000 builder's works numbers, renumbering and known disposition are listed in the table.