We are regular traveler through railways, how many of us noticed the letters mentioned in engines? And what is the abbreviation of the same? Let us discuss about the classification of locomotives.
Locomotives are classified according to their track gauge, motive power, the work they are suited for and their power or model number. Each locomotive Class Name will consist of three or four alphabets followed by a number and then an optional alphabet or two. Each of these letters can be said to be a “slot”, which can be filled by a predefined set of alphabets or numbers to denote some characteristic of the loco. The Class Name can be found painted on the front, back and sides of the loco.
The first letter denotes the track gauge. The second letter denotes their motive power (Diesel or Electric) and the third letter denotes the kind of traffic for which they are suited (goods, passenger, mixed or shunting). The fourth letter used to denote locomotives' chronological model number.
The first letter (gauge)
W – Indian broad gauge (the "W" Stands for Wide Gauge - 5 ft 6 in)
Y – Meter gauge (the "Y" stands for Yard Gauge - 3 ft or 1000mm)
Z – Narrow gauge (2 ft 6 in)
N – narrow gauge (toy gauge) (2 ft)
The second letter (motive power)
D – Diesel
C – DC electric (can run under DC overhead line only)
A – AC electric (can run under AC overhead line only)
CA – both DC and AC (can run under both AC and DC overhead line); '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 – Shunting (also known as switching engines or switchers in the USA and some other countries)
U – Multiple units (EMU/DMU)
R – Railcars
The Fourth Number – Power/Version and Fifth Letter – The Subtype
This number is called “Series” denotes different things for Diesels and Electrics. This number denotes the Horsepower rating of the engine as multiples of 1000 hp. So a 2 will denote a locomotive with an engine with more than 2000 – 3000 hp power rating for Diesel engines. However all Electrics and all non-BG locomotives, the Series notation just denotes the chronological version/model of the locomotive.
The fifth and in most cases the last letter is called a “Subtype” and is the most confusing of all. It can be a letter or a number and may arbitrarily denote anything from power rating to unique factors of the loco. The subclass annotation will be letters denoting incremental hp power in multiples of 100. “A” denotes 100 hp added to the 3000 hp, “B” denotes 200 hp, “C” is 300 hp, “F” denotes 600 hp and so on.
For example, in "WDP4D":
"W" means broad gauge
"D" means diesel motive power
"P" means suitable for passenger service
"4D" means the locomotive's power is 4,400 hp ('4' stands for 4000 hp, 'D' denotes 400 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.
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