Abstract: A road trailer for carrying both fluid and dry freight which includes an elongated bulk liquid tank which is clad with sheet metal and has a flat base surface which is stepped across its length from a forward low volume zone of the tank to a lower second level, high volume tank zone, a first pair of parallel spine beams which extend over the length of the tank and are attached to its upper surface cladding, a second pair of parallel spine beams which extend over the length of the tank, and follow the stepped contour of the base surface cladding and are again stepped upwardly to project rearwardly from the high volume zone of the tank, vertical planar spacer elements which are located in and spaced over the length of the tank and are fixed directly to the second pair of spine beams and the inner surface walls of the tank cladding, a load deck arrangement over the upper outer surface of the tank, a hitch device on the underside of the low volume zone of the tank, and a wheel and suspension arrangement which is