Abstract: Based on the air temperature data on the two different underlying surface types that one is the cement pavement and the other is the asphalt pavement from March of 2010 to December of 2003 in Zhenjiang, the climatic characteristics of icy roads were analyzed. Combining precipitation property, with or without snow cover, the daily minimum and mean air temperature, a road icing effect index was defined and the accurate rate of forecast for the different grades was checked. The results show that there is a monthly and seasonal variation for icy roads. It appears mainly in winter and seldom in November and March. Its variation trend is a contrary phase with that of mean air temperature from November to March in Zhenjiang. If it snows or has snow cover in the current day or in the previous day, the ground temperature on the cement and asphalt roads is below or equals to 0 ℃ and lasts more than 16 hours, there will be icy roads influencing the traffic seriously. It appears mainly in the nighttime for icy roads. If it is in the daytime, it has serious icy roads in other times. Meanwhile, the effect of icy roads on the traffic in the daytime is more significant than that only in the nighttime. The road icing effect index could also forecast for continually icy roads, while the false alarm rate is relatively high.

Key words: Road icing index, Classification forecast, Meteorological factor