 Snow deeper than this however can clog the brushes, and most snow sweepers cannot be used to clear snow deeper than .A more advanced version of the snow sweeper is the jet sweeper, which adds an air-blower just behind the brushes, in order to blow the swept snow clear of the pavement and prevent the loosened snow from settling.The surface friction tester is a small fifth wheel attached to a hydraulic system mounted on the rear axle of the vehicle, used to measure road slipperiness.