从全国雾天交通事故多发的10条高速公路路段中选取交通气象观测条件较好的4条路段作为研究对象，主要研究了雾天交通事故的特征，并通过雾天交通事故与能见度的关系分析，定量研究了交通事故在不同能见度区间的分布规律。与晴天交通事故相比，雾天交通事故后果更为严重，伤亡率明显增加。事故类型以撞固定物和刮擦为主。雾天事故中，肇事车辆为重型货车、中型货车和大型客车的比例比晴天增加。雾天事故的原因主要有在同车道行驶未按规定与前车保持安全距离、操作不当、低能见度下不按规定行驶。统计表明，雾天交通事故主要发生在秋冬季节的凌晨至早上时段，事故高峰期为早上7∶00左右，这与大雾日数的时间分布具有较高的一致性。70%~90%的雾天交通事故发生在能见度低于1 km的情况下，其中能见度低于100 m的区间内比例最高，为25%~50%。能见度低于1 km时，交通事故发生的概率密度随能见度增加而减小，尤其当能见度低于300 m时，交通事故发生的概率出现突发性增长，当能见度低于100 m，交通事故发生的概率密度增长到30%左右。根据交通事故在不同能见度区间的分布，将能见度对交通安全的影响划分为4个等级，实现了气象能见度到交通安全等级的转化，可为交管部门制定雾天交通事故防范对策，以及气象部门开展交通气象服务提供科学依据。

In this paper, 4 expressway sections under relatively good meteorological observation condition are selected as samples from the top 10 expressways in China with frequent traffic accidents in fog days. The main characteristics of traffic accidents in fog days are analyzed, and the distribution of traffic accidents in different visibility intervals is quantitatively studied. Compared with the traffic accidents in sunny days, the traffic accidents in fog days are more serious and the casualty rate is increased significantly. The main types of accidents are collision on fixture and scraping. The proportion of vehicles of heavy trucks, medium trucks and large buses is higher than that on sunny days. The main causes of traffic accidents in fog days are the driving in the same lane without keeping the safe distance from the front vehicle, improper operation, and driving not according to regulations under low visibility. Statistics show that, traffic accidents in fog days mainly occur in the early morning of fall or winter seasons, and the accident peak is around 7:00 in the morning. This is consistent with the temporal distribution of fog days. 70%-90% of traffic accidents in fog days occur when visibility is less than 1km. And the proportion (25%-50%) of traffic accidents occurring when visibility below 100m is the highest. When the visibility is less than 1 km, the probability density of traffic accidents decreases with the increase of the visibility. Especially when the visibility is less than 300m, the probability density of traffic accidents grows rapidly. When the visibility is less than 100m, the probability density of traffic accidents increases to about 30%. According to the distribution of traffic accidents in different visibility intervals, the influence of the visibility on the traffic safety is divided into 4 grades, and the meteorological visibility can be directly related with the traffic safety level.