Enter the classification and the road number of the vehicle in the fields above, then press the Calculate Letter button.
Note: Officially for locomotives that only have a number "Railways of Australia" rules indicated that you were supposed to add the word "LOCO" into the classification field, but some people have reported that this seems to give a different result to that actually used on the locomotive. It appears that you should leave the first field blank to get the letter that is used. As I never really worry about the check letter (it is only intended for use by the computer I need to check up this problem).
For carriages that only have names, enter the first four letters of the name and a road number of zero (i.e the Coonatto car has a coding of COON 0).
Adapted from some code by Brendan Morley.
Excerpt from "CODE OF PRACTICE FOR THE DEFINED INTERSTATE RAIL NETWORK"
2.4.1 A check letter should be included in all vehicle identification (class
and number) groups as a suffix to the vehicle number. Use of the check
letter is a security measure designed to help detect errors and inadvertent
or unauthorised changes in the alphanumeric coding.
2.4.2 The check letter should be determined in accordance with the following
(a) Alpha characters are allocated a numerical value according to their
position in the alphabet, viz A = 1, B = 2, C = 3, -----. Y = 25, Z = 26.
(b) Leading zeros are inserted if necessary between the alpha group and the
number to form a 9 character vehicle classification.
(c) Assign numerical values to each character to form a sequence a1, a2, a3,
a4, N1, N2, N3, N4 and N5, where a1 to a4 correspond to the vehicle class
and N1 to N5 refer to the vehicle number.
(d) Calculate the value of the following series:
(1 * a1) + (2 * a2) + (3 * a3) + (4 * a4) + (5 * N1) + (6 * N2) + (7 * N3) +
(8 * N4) + (9 * N5)
(e) Divide the sum by 23 and add one (1) to the remainder to give the
position of the check letter in the alphabet. A check letter character of I
is to be recorded as X, and O is recorded as Y.