Modular heavy goods vehicle comprising: a left-hand vehicle module having a left-hand longitudinal frame part that extends in the vehicle length direction and to which at least two left-hand wheel assemblies are attached one behind the other when viewed in the vehicle length direction, a right-hand vehicle module that is formed separately from said left-hand module and has a right-hand longitudinal frame part that extends in the vehicle length direction and to which at least two right-hand wheel assemblies are attached one behind the other when viewed in the vehicle length direction, and two connection units that extend in the vehicle width direction, one free end of which units is connected to the left-hand longitudinal frame part and the other free end of which is connected to the right-hand longitudinal frame part, the two connection units being designed as length-variable cross-frame modules (16, 18; 116; 216; 316) that are formed separately from both the left-hand longitudinal frame part and the right-hand longitudinal frame part, and a first of said cross-frame modules being releasably attachable to one longitudinal end of the two longitudinal frame parts (20, 24) and the other of said cross-frame modules being releasably attachable to the other longitudinal end of the two longitudinal frame parts (20, 24), characterised in that the left-hand and right-hand vehicle modules, by means of the left-hand and right-hand longitudinal frame parts thereof that extend in the vehicle length direction, are designed to be free of functional elements required for the provision of the length variation. a left-hand vehicle module having a left-hand longitudinal frame part that extends in the vehicle length direction and to which at least two left-hand wheel assemblies are attached one behind the other when viewed in the vehicle length direction, a right-hand vehicle module that is formed separately from said left-hand module and has a right-hand longitudinal frame part that extends in the vehicle length direction and to which at least two right-hand wheel assemblies are attached one behind the other when viewed in the vehicle length direction, and two connection units that extend in the vehicle width direction, one free end of which units is connected to the left-hand longitudinal frame part and the other free end of which is connected to the right-hand longitudinal frame part, the two connection units being designed as length-variable cross-frame modules (16, 18; 116; 216; 316) that are formed separately from both the left-hand longitudinal frame part and the right-hand longitudinal frame part, and a first of said cross-frame modules being releasably attachable to one longitudinal end of the two longitudinal frame parts (20, 24) and the other of said cross-frame modules being releasably attachable to the other longitudinal end of the two longitudinal frame parts (20, 24), characterised in that the left-hand and right-hand vehicle modules, by means of the left-hand and right-hand longitudinal frame parts thereof that extend in the vehicle length direction, are designed to be free of functional elements required for the provision of the length variation.