Abstract: Disclosed is a road cleaning machine including a centrifugal fan assembly that includes a fan casing including a casing inlet and a casing outlet and an impeller mounted in the fan casing and rotatable about an axis of rotation for drawing fluid from the casing inlet and directing the fluid to the casing outlet, the impeller includes a splitter wall extending outwardly from the axis of rotation to define first and second blade chambers extending from first and second faces of the splitter wall respectively, the splitter wall including a splitter wall aperture, a plurality of blades being mounted in the first and second blade chambers the impeller being configured to, during rotation about the axis of rotation, direct fluid from the casing inlet through the first and second blade chambers to the fan casing outlet, the fluid being directed into the second blade chamber via the splitter wall aperture.