تعيين مناطق بحراني وقوع تندبادها در شبكه حمل ونقل جاده اي كشور

Determination of Critical Regions of Storm Occurrence in Road Transportation Network of Iran.

Storms are atmospheric phenomena that affect the road transportation safety. Wind effects on vehicles may depend on some variables including: wind speed, angle between wind and vehicle, Aerodynamic structure of cars and road-side, specific curve of car movement direction and road surface collision coefficient and etc. Generally more attention have been dedicated to rainfall and fog risks rather than storm risks in driving but storms can also cause some dangerous situations such as rainfall, snowfall and frost which can decrease the ability of vehicle controlling to its minimum extent. Sand and dust storms generally make some difficulties for drivers on road transportation so that chain accidents and heavy traffics are some of its results. Among local winds of Iran, 120-days wind in Sistan is a famous one which blows over eastern and southeastern regions of Iran and when loading surface particles cause some sand and dust storms. Storm situation in Iran have been studied because of its great importance on road transportation. Meteorological statistics and information used in this study are in accordance with data chronological criteria including information of daily hours related to observations during 1368-77. After determining the frequency of wind speed thresholds, more than 10 m/s with the occurrence possibility of 75 percent. In 120 meteorological synoptic stations, monthly distribution of critical regions in Iran was determined and following maps were designed and finally the maps of storms critical regions in geographical information system (Arc view Software) wrere designed and examined.