The Weber-Fechner Law,which says that the relationship between applied stimulus level to human and the level of human sensation can be expressed mathematically by the exponential equation. The measured data of speed and distance-headway have proved the Weber-Fechner Law, from which very new evidences were presented. This book will mention the followings: First one is that the analyses in time-domain were made possible, and opened the door to know the time sequential change of flow by measuring each car speed and time-headway. Second one is the essence was presented of the theoretical approach to avoid the traffic congestion and forecasting it. Third one is that the basic theory of the t-s (time-space) diagram was presented, which offers the way to comprehend the complex traffic flow with a simple and visible way. Forth one is that we could solve the problems of the traffic congestion of urban and suburban road with intersections. And final one is that the way could be opened for evaluations of the flow activity (how many and how much traffic flow can carry), which can be applied to evaluate the traffic flow activity in our economical society.