Inclement weather creates a chronic hazard on Mountainous roads in Iran. Past studies indicate that road collisions rate increase during precipitation & road frosts. The goal of the current study is assessment of spatial & temporal distribution of slipperiness and road frost in Haraz and Firuzkoh roads (that are stretches between Tehran and northern provinces by crossing Alborz mountains) by using Statistical Methods and GIS techniques due to analysis of 5 synoptic weather stations. All of the stations have different situations and climates: Abali, Aghdasieh, Hammand Absard, Firuzkoh and ghrakhil Ghaemshar. The study has 2 interrelated objectives:(1) To explore any Monthly & Yearly different probability of weather conditions (Np1-Np9) and regress analysis with elevation.(2) Identification of spatial and temporal distribution of Them in the case studies. The result show that the spatial patterns for different types of road slipperiness and frost are significantly related to local parameters such as elevation and screening effects.
