Abstract：The south line of the Chengdu-Lhasa highway，which is of great importance for national defence，is one of the two main transportation corridors connecting Tibet with the inland of China. As the most dangerous traffic route entering Tibet，a 430 km long highway section (from Paksho to Nyingtri) with typical geological hazard is investigated for frequent rockfall events. Firstly，based on the EGMS methodology，rockfall frequency is estimated by combining all the possible knowledge of site investigation，experience and theoretical analysis for 19 rockfall zones along the highway section，and annually averaged probability of rockfall events under three situations of immobile vehicles，mobile vehicles and foot passengers，is calculated by using Bernoulli formula. Secondly，probability of deaths resulting from rockfalls in the 19 zones is obtained from the encountering probability and vulnerability analysis for highway users. The risk assessment indicates that (1) fatal risk of passing rockfall zones Rm4，Rm5，Rs1，Rs4，Rs5，Rs10 and Rm7，is higher than that in other rockfall zones；(2) there are little differences in traffic conditions and human activities along the highway section，hence the hazard assessment for the rockfall zones has a result，to some degree，consistent with risk assessment；and (3) fatal risk of rockfalls along the highway section is prominently higher than that of landslide hazards in some developed countries or regions.
