In 1911 a new numbering scheme was indtroduced for locomotives. It is composed from two groups of numbers separated by a comma. The first 3-digit number shows the Class, the second, 3 or 4 digit number is the engine number inside the class. This is also grouped sometimes.
The class number indicates the number of driven axles and the axle load. The first number is the number of the driven axles.
The Class 220 (former Class Ia), 4-4-0 has two driven axles, while the Class 441 (former Class IV), 0-8-0 has four driven axles.
The second and third number shows the max. axle load indicated
in the Table:
|Axle load||Tender engine||Tank engine|
Diesel engines have a letter "M" as first character in the class number, Electric locos a letter "V". This is followed by the number of driven axles and a serial number. Thus M41 is a diesel engine with 4 driven axles (actually BB), while V63 is an electric engine with 6 driven axles (actually CoCo).
For diesel electric engines the second group of numbers contains 3 digits. For diesel-mechanic and diesel hydraulic engines it is composed from 4 digits, where the first digit is 1 for diesel mechanic engines and 2 for diesel hydraulic engines. Thus M41,2015 is a diesel hydraulic engine with four driven axles.
The very small steamers were called first "Motor replacement engines" and had only a two digit Class number. This was changed in 1959, when they also got a three digit number. The Class 275 was Class 22 before 1959, and the Class 175 was Class 11.
The first diesel engines got a three digit number after the Letter M, similarly to the steamers. The two "M44" prototypes were "M424" before 1959.
When the Class M47 was purchased, the diesel mechanic locomotives were considered as obsolate. Thus the first digit af the second group at this class does not indicate the drive system (all they are diesel hydraulic), but the train heating equipment.
Although there is a tendency to give consecutive numbers for the Classes of the same group (same leading numbers), but this is often confused. While the first Kandó electric locomotives were indeed V40 and V60, the first diesel engine was M44 instead of M40. The M40 is a later engine. There is also a gap between V60 and V63: there is no V61 and V62. This is probably made to indicate the design similarity between M63 and V63.