Abstract: A collapsible road trailer comprising a central beam to which side members of the base are hinged has a tow bar which forms a sliding fit within the central beam and is locked in position by members operated by the folding down of the sides of the base. The locking members are preferably in the form of lugs engaging openings in opposite sides of the tow bar and may be fixed rigidly to the sides of the base, passing through openings in the sides of the central beam and into the openings in the tow bar when in the engaged position. Detachable wheel assemblies may have separate mudguards which are held in position by the fixing of the wheel assemblies for which purpose each mudguard may have a stay bar which is trapped between a projecting portion of the respective wheel assembly and the side of the trailer.