Route train with continuous signalling link

In a trailer for a tractor-trailer unit (1) with a traction device (8), in particular a front-mounted draw bar (9) and a rear trailer coupling, as well as a signal connection for transmitting an emergency signal from an emergency signal transmitter (12) of the trailer to a tractor (3) of the tractor-trailer unit (1), the signal connection consists of two lines routed through the trailer (2) such that they can be connected to the vehicle traveling ahead as well as to any trailer (2) attached to it, and the emergency signal is generated by the interruption of at least one line.