The influence of highway runoff on receiving water is considered serious. On the road surface and in side ditches, rubber debris from tires and automobile exhaust emission in the atmosphere and precipitation accumulate. These pollutants are discharged by heavy rainfall to the receiving water. These pollutants contain materials harmful to the human body and the ecosystem. In this study, the authors have investigated the amounts of accumulated pollutants and highway runoff pollutants. The correlation between SS (suspended solid) concentration and benzo(a)pyrene concentration was analyzed, and the mechanisms of highway runoff pollution and accumulation pollution were clarified. Benzo(a)pyrene concentration seemed to correlate with SS concentration. Therefore, the authors have anticipated that benzo(a)pyrene concentration is high in highway runoff and accumulated pollutants based on the runoff and accumulation models of SS. The result obtained using these models almost correspond to the experimental result.