Trailer with slidable tow bar equipped with a security system for protection against overcharging of the slidable tow bar

The trailer has two wheels (21) mounted on a chassis (1). A slidable tow bar (3) has a tubular fixed part (31) fixedly mounted on the chassis, and a tubular mobile bar (32) slidably mounted on the fixed part. The tow bar has a hooking ring (4) at its free end for hooking the trailer to a tractor vehicle. A support roller (6) is mounted above and in contact with the mobile bar via a bracket for supporting the mobile bar, where the bracket is fixed to the chassis. The bracket is formed by a clevis (7) and a crosspiece (8). An independent claim is also included for a road unit comprising a trailer and a tractor vehicle.