| 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 2007 the fatalities of traffic accidents on the nation's freeways was up to 5925 people, 1105 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.Continuous long and steep downgrade sections are often hazardous locations. Management measures, traffic engineering measures and engineering measures are used to solve the traffic safety problem on continuous long and steep downgrade sections. It has been proved in practice that setting up truck escape road (TER) is the most effective engineering measure by now. Because the construction cost and maintenance cost of an TER are very high, it is most important to set up a TER reasonably. The principle of setting up a TER which is studied in the paper is principal problem.The paper analyses of the study on the principle of setting up truck escape ramps at home and abroad. According to the data collected about the Mountainous freeway accident, road geometric horizontal and vertical design elements and traffic flow, a model is established which is about the relationship between out-of-control truck accident and road horizontal design elements, road vertical design elements and traffic flow conditions. Based on the model, operation process chart which is used to set up truck escape ramps is given after considering the real road environment and traffic flow condition and the principal of setting up truck escape ramps is established. |
