Characteristics of Road Surface Icing on Beijing Expressway

Based on the datasets observed by the VAISALA ROSA from 2007 to 2009, the spatial-temporal characteristics of Beijing Expressway road surface icing were studied. Firstly, the road surface icing almost occurs in the northwest region of Beijing and the ring roads of Beijing expressway, but less in the southeast region. Secondly, the frequency of freeze is closely related to precipitation and temperature; the road Surface Icing events caused by snowfall accounted for more than 75%. Thirdly, the diurnal variation of the icing events is significant on both the inside and outside lanes, more than 80% of the icing events occurred during 8 p.m. to 8 a.m., mainly after midnight. The duration of icing after midnight is mostly less than 6 hours, and the duration of the icing after 12 p.m. is shorter than that of before 12 p.m., which can even last up to 23 hours. In addition, when the icing caused by snowfall occurred, the road surface temperature and atmospheric temperature are both below 0oC, and the former is often a bit higher than the later. The surrounding wind speed is mostly below 4m/s.