Ever wondered what those WAPs and WAGs and WDMs meant on the train engines? Well, finally, I have found what they mean. Thanks Wikipedia.To see the source and lots more information, go here.

Classification syntaxes for Locomotives in the Indian Railways.

The first letter (gauge)

• W-broad gauge
• Y-meter gauge
• Z-narrow gauge(2.5 ft)
• 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.