In Japan, the number of traffic accidents in mixed traffic having the higher rate of motorcycles among the world, is increasing. Evaluation of traffic safety measures taking account of motorcycles is important. In this paper, a potential model which can express motorcycle behavior near a crossing is proposed, which is to be an essential part of the traffic simulation model used for evaluation of moped safety. The authors show concepts of a model concerning traffic situations affecting swept path of motorcycle which proceeds into a crossing, and estimate model parameters about motorcycle behavior evading an on-street parking vehicle.