Pre-nationalization , historically classified as E, A1 and 150 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 custom 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: • A –
Tank locomotives with two driving axles (A1–A10) • B – Tank locomotives with three driving axles (B1–B7) • C – Tank locomotives for rack railway (C1–C3) • D –
Tender locomotives with two driving axles (D1–D12) • E – Tender locomotives with three driving axles (E1–E7) • F – Tender locomotives with four driving axles (F1–F2) Each private railway had its own classification system at the time. For example, the
Nippon Railway used the Swiss
classification system.
1909 numbering system locomotive 58654 of Class
8620 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. • 1–999 – Tank locomotives with two driving axles • 1000–3999 – Tank locomotives with three driving axles (3900 and after for rack railway) • 4000–4999 – Tank locomotives with four driving axles • 5000–6999 – Tender locomotives with two driving axles • 7000–8999 – Tender locomotives with three driving axles • 9000–9999 – Tender locomotives with four and over driving axles 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.
1928 numbering system Because the 1909 method was about to overflow, a new system of numbering and classification came into effect on October 1, 1928. Except for Classes 18900, 8200 and 9900 being reclassified as
C51,
C52 and
D50 respectively, existing locomotives were not reclassified or renumbered. After this revision, steam locomotives were classified and numbered with a Latin letter and numerals. ; Example:
D51 498 Unlike electric and diesel locomotives, steam locomotive classifications do not include an indication of the type of power source (steam) in their class names. ; Number of driving axles :A letter indicates the number of driving axles. Number of either leading and trailing axles or axles of tenders is disregarded. :* 2 axles – B :* 3 axles – C :* 4 axles – D :* 5 axles – E ; Class : Together with the letter representing the number of driving axles, a two-digit numeral following the letter indicates a class. The number distinguishes tank locomotives and tender locomotives. :* 10–49 – Tank locomotives :* 50–99 – Tender locomotives According to this numbering method, D51 498 means locomotive number 498 of
Class D51, which is a class of tender locomotives with four driving axles. == Electric locomotives ==