Study on Reasonable Value of the Largest Length of Straight Line Section on Freeway

From the viewpoint of vehiclei¯soperation state, vehiclei¯srunning on straight line section of freeway is divided into three courses, ii¤ei¤, accelerating course, even-speed course and decelerating coursei¤Running tiand distance in the three courses were analyzedi¤Taking the largest length of straight line section on which the running time is no more than seventy seconds as the control condition, the largest length of straight line section calculation model based on operation speed of freeway was presentedi¤The model shows that the largest lengt straight line section at speed of 120 km/h is less than that at twenty multiples of design speed on freeway and it needs to be determined by operation speed of start point and end point of adjacent curve for freeways with other data, the regression model between operation speed of car and plane curve radius of freeway was established and the calculation example was presentedi¤The largest length of straight line section of freeway determined by operation speed can meet driveri¯sdemand better, and its calculation model can provide for freeway design and safety auditi¤