The APT (Advanced Passenger Train)

Introduced in 1979, the APT, as it is normally referred to, was an InterCity Development train, uniquely designed to provide faster journey times on the West Coast Main Line, culminating in a passenger relief service between London and Glasgow three days a week between 1983-85. Then from 1985-87 it was used solely for development purposes of future electric locomotives.

Built by BREL at Derby, the allocation, which was divided between Glasgow Shields Electric Traction Depot and Crewe ETD, consisted of six rakes and a spare driving vehicle, numbered 370001 - 370007 (Class 370). Each rake would contain up to six articulated trailer vehicles and one non-driving motor vehicle, so that each train set would comprise of two such rakes with the non-driving motor vehicles being situated in the centre of the formation.

To meet the criteria for faster journey times the decision between straightening the track and tilting the train over existing track had to be made. The decision went in favour of the tilting train, hence the special features of the APT were developed.

1. Hydraulically operated tilt system, controlled by sensors on the bogie frames.
2. Hydro-kinetic braking system, providing efficient high speed braking to stop the train within existing signalling distances.
3. Lightweight steel bogies, incorporating specially designed axles for use on the hydro-kinetic braking system, air bag secondary suspension of the vehicles and swinging bolster, jacks and control equipment for the tilt system.
4. C-APT (Drivers Aid Control - 'Control APT'), electronically controlling the indication of enhanced line speed and restrictions to driver, and acting on his response to these signals.
5. Four, vehicle mounted, 1000 hp, ASEA LJMA 410F separately excited traction motors, being controlled by power thyristors for variable excitation.

The above items were developed to give a maximum line speed of 155 mph and with tilt the APT could consequently negotiate curves 20%-40% faster than conventional trains.