Influence mechanism of mass fog on Highway traffic safety

According to statistical analysis of historical data from the meteorological observations of Shanghai-Nanjing Highway, we found a series of features of mass fog. It always happens suddenly after sunrise and changes the visibility by leaps and bounds in a uncertain area. Because of these features, mass fogs often lead to a chain rear-end accidents resulting in many casualties on the highway. This paper analyzes direct and indirect impacts of the mass fog on the highway traffic safety. The direct impacts are the reduction of road surface friction coefficient and visibility. And the indirect impact is mainly reflected as speed changes. Road adhesion reduction factor will lead to skidding or drifting of high-speed vehicles, which increases the drivers´ psychological pressure and forces the driver to drive with a lower speed. It is difficult to access to the effective traffic information when necessary because of the reduction of visibility, which will increase the driver´s psychological pressure. In this case, the drivers can not accurately adjust driving behavior and the traffic accident will happen.