Frost and sliding in Iran’s mountain roads cause dangerous conditions for road transportation. In this study, two goals are followed: Firstly, description of a method for a determining the likely occurrence of the critical condition of frost and sliding using the climatic conditions matrix along the Karaj- Chalous road (which is full of – traffic and mountains roads of Iran, connecting the Northern provinces to Tehran the Alborz heights). Secondly, the spatial and temporal analysis of frost using statistical analyses and GIS. One of the most important conclusions of the study is that there is a direct connection between the frost and height phenomena as by increasing the heights, the frost phenomenon occurs as soon as possible and is prolonged. From the viewpoint of spatial distribution, the studied mediate parts (that is, Karai’s kms 43 to 128) are affected by drastic frost and from the in viewpoint of temporal distribution the N5, N6 and N9conditions (accounted as dangerous frost conditions for transportation) have been concentrated in December, January and February.
Key words: Frost, sliding, Karaj – Chalous road, climatic conditions matrix, road transportation.
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