Multi-system (rail)

From the 1950s onwards, the emerging formation of the European Union, and the consequent increase in the amount of cross border traffic, along with the addition of a 25 kV 50 Hz AC system in France in addition to the older 1.5 kV DC system, gave rise to the need for multi-voltage locomotives.

Cheap loans to stimulate economic development in the 1930s gave rise to the several schemes of 1.5 kV DC electrification, mostly completed post war, notably between Liverpool Street and Shenfield, and the Woodhead Line.

All the driver had to do was shut off power and coast until clear of the neutral section; the system automatically opened the circuit breaker, detected a change in voltage and switched over the transformer to the correct input voltage setting, then closed the circuit breaker.

The British Rail Class 700 electric multiple unit, manufactured by Siemens Mobility, is used on the Thameslink network.

In the United States private companies undertook electrification independently, resulting in divergent systems.

Thus the New Haven EP-1 had to support three separate electrification systems: 660 V DC via third rail, 660 V via pantograph, and 11 kV 25 Hz AC via pantograph; in order to make a 27-mile (43 km) journey from the New York Central Railroad's Grand Central Terminal in New York City to its own station in Stamford, Connecticut.

While traveling between Mount Vernon East and Pelham, trains switch between the third rail and overhead electrification systems without stopping.