Abstract: An apparatus for controlling the regulator of a device for spreading salt and the like onto road surfaces, the apparatus comprising: a sensor for measuring the temperature of liquid on the road surface; a collector for liquid removed from the road surface, adapted for operation on a moving vehicle; a device operatively associated with the collector for measuring the concentration of salt in the collected liquid; and, a device operatively associated with the collector for measuring the quantity of liquid present per surface unit area of the road, based upon the quantity of collected liquid and a measured factor related to movement of the vehicle along the road, whereby sufficient information is available from the apparatus for regulation of a device for spreading salt and the like to achieve a salt concentration on the road surface just sufficient to avoid freezing at any predetermined tempertaure and for any predicted quantity of precipitation.