The quality of pavement runoff water from a 275-m motorway section has been studied for 1 year, during which approximately 50 rain events have been sampled. Two different types of pollution have been revealed. One type can be defined as chronic and includes suspended solids, chemical oxygen demand, total hydrocarbons, zinc and lead. The second type can be considered to be seasonal and incorporates chlorides, sulfates, suspended solids and heavy metals due to the use of deicing salt in winter. Pollutant loading as regards lead appears lower than in previous studies because of the increasing number of vehicles using unleaded gasoline. The study conducted on the sources of pollution and on heavy metal fluxes (Pb, Cu, CD, Zn) released by the traffic has been used to assess a mass balance with respect to pollutant loadings removed by runoff waters. It seems that a large proportion of the lead concentration may disperse in the atmosphere, whereas cadmium sources may be ill-identified or underestimated.