Plain Highway Traffic Accident Prediction Model Study

In China, recently, although a large amount of manpower and material resources have been invested to improve safety on national highways, the severity and frequency of crashes is still the social big challenge, especially for the freeways. Since the first national freeway was open to the traffic in 1988, the number and fatalities of traffic accidents kept rising. In 2004 the fatalities of traffic accidents on the nation's freeways was up to 6235 people, 1823 people died every ten thousand kilometers on average, which is far higher than the level of common highways. This is quite different with characteristics of western countries, it was said that number of fatal accidents of foreign freeways is only 1/3～1/2 of that of other highways. Analyzing the effect of factors on traffic accident would significantly enhance the efforts of traffic engineers to determine suitable countermeasures to reduce the occurrence and severity of crashes.The study analyzed the relationships between geometric design elements and traffic accident, traffic flow features and traffic accident, environmental elements and traffic accident, which were based on the presumption that the drivers on freeway were in better conditions of steering and had rich experience of driving. The finding of the freeway-Jing Jintang-in plain terrain is that the ideal geometric design is not a main factor to lead to traffic accident. there are strong and obvious correlation between traffic flow features and traffic accident, environmental elements and traffic accident, such as heavy vehicle rate, hourly traffic volume, speed differential between cars and heavy vehicles, number of access, effect of fog, effect of district(city or country), effect of way(up or down) and effect of time(day or night). By means of nonlinear regression the traffic accident prediction models were constructed, the dependant is traffic accident rate including three types which are only property damage accident rate, casualty accident rate and the entire accident rate. The independents are the traffic flow feature and environmental elements. The three models are the theory for traffic engineers to predict the occurrence and severity of crashes based on real-time traffic flow data.The results of this research are unable to represent the whole freeways in Chinese plain terrain. However, the freeway- Jing Jintang-has the common characteristics of all the freeways in plain terrain, namely, better geometric design standard and fewer grades, it is a good chance to explore the main causes that lead to traffic accidents on freeways through the example of Jing Jintang freeway. The paper used traffic flow and environmental data when traffic accident prediction model was constructed, which were seldom considered together in researches on traffic accident prediction models in China.