The classification syntaxes
The first letter (gauge)
W-Indian broad gauge (The "W" Stands for Wide Gauge - 5 Feet)
Y-metre gauge (The "Y" stands for Yard Gauge - 3 Feet)
Z-narrow gauge(2 ft 6 in)...
more...
N-narrow gauge (2 ft)
The second letter (motive power)
D-Diesel
C-DC electric (can run under DC traction only)
A-AC electric (can run under AC traction only)
CA-Both DC and AC (can run under both AC and DC tractions), 'CA' is considered a single letter
B-Battery electric locomotive (rare)
The third letter (job type)
G-goods
P-passenger
M-mixed; both goods and passenger
S-Used for shunting (Also known as switching engines or switchers in United states and some other countries)
U-Electric multiple units (used as commuters in city suburbs)
R-Railcars
For example, in "WDM 3A":
"W" means broad gauge
"D" means diesel motive power
"M" means suitable for mixed(for both goods and passenger)service
"3A" means the locomotive's power is 3, 100 hp ('3' stands for 3000 hp, 'A' denotes 100 hp more)
Or, in "WAP 5":
"W" means broad gauge
"A" mean AC electric traction motive power
"P" means suitable for Passenger service
"5" denotes that this locomotive is chronologically the fifth electric locomotive model used by the railways for passenger service.
