Some bus types also benefit from combinations of grid frame and ladder frame design. This enables the front section to the rear axle of urban buses to be designed as a grid frame and the area behind the rear axle as a ladder frame. The middle section of coaches can be in a grid frame, for as large a luggage compartment as possible, combined with front and rear components in a ladder frame. Many 2- and 3-axle buses with masses of about 10 to 24 tons are based on an interconnected frame construction. Other means of assembling the bus bodywork are integral design, semi-integral design and ladder frame design.