198608 – Howker – “Trivial Pursuit” & Brief History of Automatic Train Control (ATC)

The use of the term “Automatic Train Control” (A.T.C.) was, by definition, wrongly named! It was neither truly automatic nor did it totally control trains. However in the historical context, A.T.C. has been the standard description for many years and so the mnemonic is used throughout this brief paper.

True A.T.C. has only come into being in the last 20 years and embraces two different principles, namely:
A.T.O. – Automatic Train Operation
and A.T.P. – Automatic Train Protection.

The usage over the past 100 years of A.T.C. is really A.T.P., and this is recognised by most railways who now use the more truthful definition, A.W.S. – Automatic Warning System.

A.T.C. (or A.W.S.) has been around for a long time.

It was recognised early into the Railway Age, that having good signalling (interlocking block) with good brakes (automatic application in the event of train breaking) were still not sufficient to run a truly safe railway.

Giving the driver good brakes and presenting him with good signalling was alright, as long as the driver didn’t disobey (or miss) the signal indications so the minds of the Great Engineers of the 1880’s were put to work to solve this problem.

As can be seen, in the early days A.T.C. was only used to apply brakes at a signal showing stop.

The different methods devised can be broken down into four methods.
1. Mechanical – empty the train pipe (historically known as train stop method).
2. Mechanical/Electrical – used contact ramps plus electrical signals. (Most types emptied train pipe – some versions gave audible/virtual signals).
3. Electrical only – Coded Track Circuits (cab signalling plus some form of braking if not acknowledged.
4. Electrical – other means of passing signal from train to train (includes A.W.S., transponders, radio etc.).