Accommodation bogie, from APT-E trailer car, British Railways, 1972.

The APT-E is a semi-permanently coupled articulated train. Unlike the power cars, which have dedicated leading bogies carrying traction motors, the APT-E’s unpowered trailer cars are suspended at either end by a common bogie. This has the advantage of reducing the number of bogies and wheels as well as reducing the overall weight of the train, while making for a more comfortable ride and potentially increasing seating capacity. When an APT-E trailer car is removed from the train formation, temporary accommodation bogies are attached to enable movement of the vehicle.