Design Methods for Safety Enhancement Measures on Long Steep Downgrades

Restricted by the rolling terrains of mountainous areas in western parts of China, long steep downgrades are very common in mountainous freeways. Influenced by the factors like high altitude, big elevation differences, and the severe weather condition e.g. black ice, heavy snow and thick fog, most long steep downgrades turn to traffic accident prone sites. Moreover, once traffic accident happens, the severity is high and the society influence is wide. So the overall safety level of mountainous freeways has been greatly influenced by the safety level of long steep downgrades. In this paper, the safety classification methods and the general design principles of long steep downgrades and the design principles of safety enhancement measures for different sections of long steep downgrades are put forward based on the investigation of typical long steep downgrades in freeways. Then the methods for the safety enhancement measures design on long steep downgrades according to the safety level are expounded. Moreover, the design process of the safety enhancement measures design is presented. The presented research finding provides an important support for the safety enhancement measures design on long steep downgrades.