Transportation sector accounts for the largest part in consumption of gasoline and gas oil. Increase in fuel consumption along with decrease in energy efficiency as well as energy conversion with high waste has caused irreparable damages to environment and economical- social development. In addition, raising the price of all types of fuels and rationing these products, has made it necessary to pay attention to this section. In this paper, traffic flow of Garmsar-Semnan road in Iran as a case study will be analysed using simulation by CORSIM software. Then, by changing geometrical parameterss in the road, the changes in fuel consumption will be examined. Geometrical and traffic information related to the road under study has been obtained through measurement in the path and field perception. Furthermore, to validate the results of the fuel consumption of used software, a field survey was conducted which indicates slight difference between the actual values and the results of the software. The results of the changes in geometrical factors show that simultaneous change in slope and elimination of curves in this road will have the greatest impact in reducing fuel consumption of the vehicles and consequently reducing the environmental pollution