Kryšpín's system

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Kryšpín’s system is a locomotive class naming method used in Czechoslovakia from September 1923 to the late 1980s. It was created by Ing. Vojtěch Kryšpín, a locomotive plant director, and approved by the Ministry of Railways in September 1923.

Standard gauge class names follow the form Y ASW.GNNN. Y is the vehicle type. A is the number of live or coupled axles. S is the speed code, calculated as (max speed − 30) / 10, with special rules: if the max speed is over 120 km/h, S is 9; if the max speed is under 30 km/h, S is 0. W+10 is the weight per live or coupled axle in tonnes (for example, W = 8 means 18 tonnes per axle). G is the design group, used to distinguish different designs that share the same Y, A, S, and W. NNN is the serial number, starting at 001 for the first locomotive in that class.

For narrow gauge, the class is Y AW.GNNN, with the same meanings for the other symbols.

Electrification in Czechoslovakia historically used two main systems: 3000 V DC in the north and 25 kV AC (50 Hz) in the south. Electrification expanded significantly in the 1950s, and AC locomotives became easier to build and more economical. Before the big electrification, other systems, including three-phase, were used. Today the Tábor–Bechyně line remains at 1500 V DC. The E class covers locomotives operating on either 3000 V DC or 1500 V DC.