Impact of Road Geometry and Surface Types on Fuel Consumption and Greenhouse Gas Emissions

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Nowadays, it is globally accepted that vehicle gas emission is a significant source of air pollution and climate change. Correspondingly, vehicle operators are interested in reducing energy consumption and accordingly fuel costs. The paper explores the impact of road geometry and road surface types on vehicle emission and fuel consumption using the Highway Development and Management Four (HDM-4) Tool emission modeling software. The analysis was based on data acquired from three asphalt concrete (AC) and two gravel roads located in different areas of Ethiopia. In this regard, the following data were collected: Road network; Vehicle Fleet; and Work Standards in respect of improvement and maintenance. The data were entered into HDM 4 and analyzed. The results indicated that the effects of road geometry that is: rise and fall; curvature; and also vehicle speed; altitude and pavement surface types are important and should be given an emphasis on vehicle emission and fuel consumption evaluations. In all considered road sections, the study found out that emissions and fuel consumption have a direct relationship with rise and fall. Change of curvature is also related to changes in emission and fuel consumption. At higher and lower curvatures and at lower rise and fall, both emission and fuel consumption were maximum but at some point in between the curvatures, emission and fuel consumption became minimum. At higher rise and fall, emission and fuel consumption became minimum when curvature got close to zero. It was also found out that speed has a relationship with emission and fuel consumption. When the speed lies between 50km/hr to 70 km/hr, maximum energy saving and minimum emission were achieved. Impact of altitude on emission and fuel consumption was also investigated. Both emission and fuel consumption increased as altitude decreased. Another finding was that emission and fuel consumption are most sensitive to road surface types. Asphalt Concrete (AC) generated most fuel savings and reduced emission compared to Double Bituminous Surface Treatment (DBST) and Gravel roads. It is expected that the findings of this research will provide insights for policy makers when consideration of strategies for improving road design to reduce vehicle emissions and fuel consumption in Ethiopia.



Rise and fall, Curvature, Speed, Altitude, Fuel consumption, Emission