To excactly restrain racing by providing a means adjusting a sand quantity on the way of the discharge pipe of a sand tank, controlling changeover of air flow from an air piping, providing a sand/air mixer on the confluent part, and scattering a proper quantity of sand when there is possibility to generate racing on a frozen road and the like.

When during running of a truck or the like on a frozen road or after driving for starting, wheels W1 are apt to be in racing, right and left adjusting means 6 are adjustingly controlled so that a specified quantity of sand flows from a sand tank 3 (the other side is omitted because of similarity) into a sand discharge pipe 5, and further a first changeover valve 111 and a second changeover valve 112 are respectively controlled to open. The specified quantity of sand in the sand tank 3 flows into a mixer 7 through the sand discharge pipe 5, and exhaust gas from an engine En flows into the sand/air mixer 7 through an throttling 71. These mixtures are well mixed, and scattered from a blow-off port 121 onto the road surface R of a frozen road or the like directly in front of the right and left driving rear wheels W1.