These special trailers will be used for tunnelling in London. They are specially equipped due to their construction.
The rear axle is detachable and can be locked while driving. The trailers have plug-in platforms and are extremely narrow with a high payload. This, in turn, has to do with the fact that the tunnel radius is extremely small and manoeuvrability must be ensured. Furthermore, they are compressed air-braked and equipped with a special lighting system.