Swiss Re 4/4 Locomotives: How Switzerland Pioneered High-Speed Electric Rail Travel in 1946

In 1946, the Swiss Federal Railways (SBB) introduced a new generation of lightweight, high-speed electric locomotives that would set a benchmark for post-war European rail traction. The Re 4/4 class, rated at 2,400 horsepower, was designed specifically for fast express passenger services linking Geneva, Berne and Zürich.

A total of 26 locomotives entered service, each weighing just 56 tonnes, a dramatic reduction compared with the earlier Ae 3/6 class, which weighed approximately 95 tonnes and dated from the 1920s. This significant weight saving delivered major operational benefits, particularly on mountainous routes.

Each Re 4/4 locomotive rode on Bo-Bo bogies, with two traction motors per bogie driving the axles through a flexible transmission. The resulting 14-tonne axle load allowed these locomotives to negotiate the tight curves of the Gotthard line at speeds of up to 46.6 mph, while maintaining 77.7 mph on curves with a radius greater than 41 chains.

Designed to match the emerging lightweight coaching stock, the Re 4/4 locomotives typically hauled trains of 300–350 tonnes, often formed of ten coaches. Safety glass was fitted throughout, and advanced control systems allowed multiple working and push-pull operation, enabling trains to be driven from either end.

Modern safety and braking equipment was a key feature, including a dead-man’s handle, automatic train stop, quick-acting compressed-air brakes optimised for high-speed use, and regenerative braking. Extensive use of welding in bogie construction helped reduce overall mass, while the locomotive body employed all-steel construction for durability.

The Re 4/4 class demonstrated how thoughtful engineering could combine speed, safety and efficiency, and remains a landmark in the evolution of high-performance electric locomotives.