In the three elements（People，Vehicle，Road）of traffic accidents，whether based on official disclosure data or data collected by research institutions，the problem of human beings still occupies the most important position；the analysis on database finds that the proportion of accidents directly related to the problem of the vehicle itself is extremely low（below 0.3% for many years）；and through in-depth analysis on the causes of traffic accidents in the accident database over the years，it is found that the problem on road facilities is a very important factor in traffic accidents，and its impact on the cause of accidents is much higher than the vehicle problem. This article is based on the typical case study of SHUFO with the “In-depth investigation” of the Shanghai Traffic Police Force and the collected road traffic accident database. It analyzes the current characteristics of the hidden dangers of traffic facilities，the hazards to traffic safety，and the deep causes of the issues.