This part of ISO 1726 specifies dimensions to ensure interchangeability between a low coupling height tractor vehicle and a coupled high-volume semi-trailer, the two together constituting a high-volume articulated vehicle. It specifies certain interchangeability dimensions, including those of the optimised gooseneck contour, as well as operating dimensions related to angle values. The specifications are primarily intended to permit semi-trailers to be coupled with two-axle tractors. However, three-axle tractors are not excluded, provided they are in compliance with the requirements of this part of ISO 1726. This part of ISO 1726 does not provide limitations of maximum gross mass and overall dimensions, which are generally laid down by legislative requirements.