As this happens, the coupler between the buffet car and the first of the First Class coaches uncouples.

BBC: Hatfield: The accident in detail

The court was told a coupler which had been attached to the broken-down track maintenance wagon broke, allowing it to detach from the train which was pulling it.

BBC: Runaway Tube train: Operators fined ?300,000

During his next shift, Fyodorov read an order from the stationmaster: from now on, senior switchman comrade Fyodorov was to receive an additional fifty rubles a month, and he was temporarily being appointed a coupler a responsible position that many aspired to.

NEWYORKER: Among Animals and Plants