Abstract: An analisis for the car-foliowing characteristics of a row of vehicles running on the same lane is made in this paper.Also the operating using the car-following function,by which a mathematical model for directive traffic passing a signalized intersection is set up.Further more,we can calculate the distance,speed and acceleration of a car in a row of vehicles at any time with computer so as to put it into the application either for line control or computation of the passing capacity.