>>1259796I think it's just the London Underground which has this.
It's a Battery-Electric loco which is mainly used for maintainance works. It conforms to the tiny loading gauge which deep level lines have, but can also do work on sub-surface lines.
The loco has 4th Rail shoes which allow it to run normally, but it also has a large battery bank which can be charged while running on live lines. This allows it to run when the 4th rail system is shut off for maintenence work.
