車流混亂為交通事故發生的主要原因。因為在混亂的車流情形下，駕駛員之判斷 負荷加重，車輛之間的衝突可能性增加，各類型碰撞之機會增加，因此，發生車禍的可能性 也增加。故本文按過去之肇事經驗，由車流分流觀念出發，探討車流各行其道對交通安全提 升的作用。更因為我國機車數量龐大，故車流各行其道的意義，就特別顯著。本文亦特別就 機車道之車流特性加以分析，以探討其對交通安全之影響。另一方面，所謂車流各行其道的 意義尚包括公車專用道之分流措施，此點亦是目前我國都市道路的重要措施，故亦納入本文 之研討之中。綜合而言，車流各行其道係指以運具區分，來分配道路空間，以便減少不同車 種間的衝突，達成提升交通安全的目的。

　　　　　Flow chaos under mixed traffic can increase accident rate. Under mixed traffic the road user needs to pay more concentration on the driving process. The potential of conflicts among different types of vehicles also increases. To reduce the conflicts and enhance traffic safety, a separated flow concept seems to be more suitable for a flow condition with mixed traffic, especially for the traffic with high composition of motorcycles and buses. In this paper, the safety effect of bus lane and motorcycle lane is analyzed. It is hoped to create an entire concept of lane distribution in street layout.