Based on traffic surveys and data collection methods,statistical analysis is used to study the urban expressway lane free-flow headway distribution,and the headway distribution is obtained with a negative number.By using mathematical statistical methods for analysis and processing of the measured data,it is determined that if the leading vehicle is a car and follwed by a taxi,the space headway is a larger,the space headway is smaller if leading vehicle is a taxi,followed by a car.Flow rate is inversely prop...