Friends of the Rail Forum

A thread on railroad.net just prompted me to look up the details of the cab signalling which Britain's Great Western Railway used in its steam locomotives from 1906. I've seen it on preserved GWR locos.

See Wikipedia and The Great Western Railway Automatic Train Control to share in the fruits of my research.

I believe any heritage steam locomotives which are certified for main line running in the UK today (and that includes the newly built A1 referred to elsewhere on this forum) must be fitted with modern train control equipment. Apparently it's quite a challenge to find space to fit in on some types of loco.

Finding space is not the only challenge. All UK trains on the main lines are required to be fitted with logging and recording equipment, somewhat like a 'black box' for railways.

Besides the long-standard AWS equipment and possibly also ATP, this additional stuff has to record all manner of driver interactions and loco running parameters, including regulator position, reverser position, brake lever position, time, speed, distance, steam pressures, brake pressures, AWS status, etc, etc. I am not sure whether it also incorporates accelerometers, but I seem to recall that is a requirement as well.

This means that all manner of interfaces and transducers between the mechanics of the loco and the electronics of the recorder need to be designed and fitted in a hostile environment where they were never originally envisaged by the original loco designer. In addition, this means that a reliable, high quality electrical supply needs to be provided along with a substantial battery and inverter backup. I note that the A1 is using an axle-driven alternator on the tender to supply such electricity. Shore power will be used when stationary. It is also being fitted with a steam turbo generator as well. Additional electrical demands arise from the use of electric marker and code lights in place of the original oil ones.

Add to this the A1's need to mount two air pumps and air-vacuum proportioning valves to allow for air braking on modern stock simultaneous with the old vacuum brakes for heritage working and you begin to see why space become a problem. Incidentally, on the A1, they mounted the air-pumps underneath, between the frames of the tender.