Abstract: The contribution of national trunk highway system to traffic safety was analyzed based on a large quantitative data collected from 7 freeways and 6 minor arterial highways. Firstly, the accident rates reduced by the use of trunk highways were established when trunk highways were compared with their competitive minor highways. Then, the economic loss for accidents occurring on trunk highways was determined based on statistic analysis. Secondly, the methodologies to calculate the lives saved, the injuries avoided, as well as the economic gains from the use of trunk highways were summarized. Then, Shen-Da Freeway and Cheng-Yu Freeway were selected as two cases to illustrate the use of the methods given above. Finally, the contribution of the whole national trunk highway system to traffic safety was estimated, which showed the fact that this system prevented nearly 900,000 accidents, spared the lives of at least 100,000 people, avoided injuries of 580,000 people, and saved economic gains of 12.5 billion RMB Yuans.