The Research For The Evaluation To Traffic Safety Condition Of Mountations Freeway

The path condition was one of the important factors of affecting the traffic safety to mountainous freeway. Because the conditions of terrain and geology which the mountainous freeway located were quite complex, its design target would often be big limited. So it was usually difficulty to fully satisfy the request of driving safety. And the mountainous freeway also had many potential safety hazards, although road sections'linear conditions meet standards. The existing results of researching for road traffic safety technology issues at domestic played a very good positive role on the protection of the mountainous freeway traffic Safety. But it still lacked sufficient theoretical support and practical experience. Which reflected in that major and malignant traffic accidents occurred frequently on many mountainous freeway. And the operation of the traffic safety issues were still quite prominent. The methods, indicators and systems to evaluate mountainous highway traffic safety that both mature and in line with China's national conditions were not yet formatted. Therefore, carrying out the research of evaluating the traffic safety system for the operation of mountainous freeway, and according to the results proposed corresponding safeguards. That was of great significance to reduce freeway accident rates and improve the level of traffic safety.This paper has mainly carried on the research of the traffic safety evaluation that aims at the operation of the mountainous freeway of Longli in Zhejiang province. First aimed at traffic accident's occurrence to have the random characteristic, the paper chose 5 methods of distinguishing the accident black spot to carry on the analysis and compare the advantages and disadvantages. And the paper used statistical analysis for the traffic accident materials of Longli freeway in last 3 years and determined the black spots setion. Have divided five type road sections based on the plane curve radius and the lengthwise grade value, the paper take the method of running speed computation which Recommended by Road safety Assessment Guide "JTGT B05-2004" to complete the computation of running speed of LongLi freeway's sections. And the paper carried on the overall evaluation of LongLi freeway's traffic safety using the design conformity evaluation and the running speed coordination evaluation. Based on the truck brake hub temperature predicted model with mature technology and high reliability to the large longitudinal downgrade, the paper used the 20t and 30t trucks which had big proportion in the accident vehicle types as the evaluation vehicles. Through computing the temperature predicted value to appraise the traffic safety for the large longitudinal downgrade of LongLi freeway, and this paper has mainly obtained the following results.(1) Aimed at traffic accident's occurrence to have the random characteristic, the paper chose 5 methods to distinguish the accident black spot, which is the Accident frequency method, Accident rate method, Matrix method, Quality Control Method and Cumulative frequency method. These 5 methods were analyzed and compared the advantages and disadvantages, The results show that the cumulative frequency method has the characteristics of small economic costs, high reliability, reliable analysis results and easy to distinguish the black spots section;(2) The paper used the cumulative frequency method to analyze the traffic accident materials of Longli freeway in last 3 years. Based on using the position of cumulative frequency of 15% to 20% "mutations in the curve" in the accidents cumulative frequency curve as assessment criteria, the paper obtained the evaluation index that if the section of Longli freeway accident rates were not less than 3 times/0.5km,it was the accident black spots section. So the paper determined the 26 sections of Lishui direction and 12 sections of Longyou direction in the Longli freeway for the accident black spots sections;(3) The survey data of number of freeways showed that trucks was essentially to slow down in the 2% to 3% of the section. But "Guide" provided that trucks was to accelerate or constant speed in the less than 3% longitudinal freeways. That was big difference with the actual situation. So the paper recommended that the standard of longitudinal changes from 3% to 2% in the trucks operating speed prediction models. That could make the standard of longitudinal value in the trucks operating speed prediction models of the "Guide" more reasonable;(4) Through the analysis of the operating speed prediction to all sections of Longli freeway, The paper found that the speed difference was lOkm/h or less of 95% adjacent sections, and the difference of road speed and design speed was 20km/h or less of 96% sections. That showed that the overall coordination of Longli freeway traffic safety was better;(5) Based on the truck brake hub temperature predicted model to the large longitudinal downgrade, which had mature technology and was revised after extensive testing. Because its calculation process was too complex, the paper used the Visual Basic to establish its computation auxiliary program with the methods of selecting structure statements and object-oriented. So it became simple to calculate and convenient to apply of the truck brake hub temperature predicted to the large longitudinal downgrade;(6) The paper used the computation auxiliary program that the truck brake hub temperature predicted model to the large longitudinal downgrade to compute the truck temperature predicted value for the large longitudinal downgrade of LongLi freeway. The paper found that the brake temperature value which using the engine auxiliary braking was low 15℃～60℃to use the exhaust auxiliary braking in the situation of consistent vehicles load and road condition.This paper has mainly carried on the research of the traffic safety evaluation that aims at the operation of the mountainous freeway. Trough the search of accident black spots, the analysis of coordination to operating speed, the analysis of temperature predicted to the large longitudinal downgrade and proposed the improvement measure according to the measure results, that had the vital significance to remove the accident potential, reduce the traffic accident's occurrence and reduce the traffic accident economic loss.