The quantity of pollution (Na +, K +, Ca ++, Mg ++, SO 4 −−, Cl −, NO 3 − and suspended solids) leaving a road surface from vehicular spray is difficult to measure directly since it is dependent on vehicle intensity, rainfall duration, wind speed and direction. Attempts have been made to obtain measurements by an indirect procedure involving total rainfall and volumes draining off the study area. Results show that water quantities lost by airborne dispersal are initially influenced by antecedent weather conditions and that values derived are only applicable to the conditions prevailing at time of measurement. Significant quantities of ionic and suspended solids are removed by this mechanism particularly under light rainfall conditions.