Japan Railways locomotive numbering and classification

This page explains the numbering and classification schemes for locomotives employed by the Japanese Government Railways, the Japanese National Railways and the Japan Railways Group.

Prior to the nationalization of Japanese railways in 1906 and 1907, the government-run railways had numbered their steam locomotives only with serial numbers without consideration of the types of the locomotives. From the beginning of the Kobe–Osaka railway in 1874, they allocated odd numbers to locomotives in Tokyo area and even numbers to locomotives in Kobe area, but this was not maintained after the completion of railway between Tokyo and Kobe in 1889. Later, some locomotives, such as Classes A8 and B6 and rack railway locomotives, were renumbered to make groups for easy recognition of classes.

Classes were introduced by Francis H. Trevithick (1850–1931), a grandson of Richard Trevithick employed by the government of Japan for supervision of rolling stock management. He classified the locomotives with one Latin letter (A through Z), which was then expanded to use two letters (AB, AC, AD, and so on).

Later, this simple method was revised to use one letter and one or two digit numerals with consideration of locomotive types. The meanings of the letters were as follows:

Following the railway nationalization, in 1909, the railway authority adopted a new system in which locomotives were numbered and classified by four-digit numerals. All existing locomotives were reclassified. Numbers 1 through 4999 were allocated for tank locomotives and 5000 through 9999 were allocated for tender locomotives. Here the classes and the numbers acquired a distinct relationship. Locomotives were grouped in numbers and the classes were represented by the earliest number of the group.

Numbers within a class were serial in principle. When the number overflowed (as in Classes 8620, 9600 and 9900), one digit was added to precede the four digits to make the numbers five digit. Class 18900 (later reclassified as Class C51) was exceptionally five digit from the beginning.

This numbering and classification rule survived the revision in 1928. Non-standard locomotives that joined the national railways by means of purchase of railway companies were numbered in accordance with this rule even after 1928. Locomotives numbered and classified under this rule includes the locomotives used until very last days of JNR steam locomotives in the 1970s.

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