Estimation of vehicular emissions and fuel consumption on road links using HDM-IV in Ghana - A case study on the George Walker Bush Motorway (14.1km) Accra

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November, 2016
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Fuel consumption and vehicular emissions from traffic are major constraints in sustainable environmental development. Vehicular emissions and fuel consumption have increased in recent years due to rapid growth in world traffic resulting in an increase in associated problems such as cancers, respiratory diseases, global warming etc. Thus, strategies for the reduction of road traffic-generated fuel use and emissions have become issues worth examining. This study looks at the estimation of vehicular emissions and fuel consumption on the 14.1km section of the George Walker Bush Motorway in Accra, Ghana. The Highway Development and Management Tool was used for the estimation of fuel use and vehicle emissions using data from secondary sources. Key data collected were traffic volume and composition, vehicle characteristics, pavement characteristics and climate data of the study area. Three options were analyzed using the HDM-4 software; the base case or do nothing consisted of the road as two-lane asphalt surfaced road with routine maintenance only for the life span of the road. The two project case options were also explored; two lane road with routine maintenance and an overlay in the second year. Also, reconstruction of the road into a 3-lane dual carriageway. This option also will routinely maintain and overplayed in the 10 year intervals. Each project case was analyzed and compared with the do minimum case. The study showed that, total emissions (CO2, CO and NOx) in 2012 on the study road saw a reduction of about 5,056 tonnes for the 3-lane dual carriageway as against the ‘do nothing’ alternative. Comparing with the overlay alternative, the 3-lane dual carriageway also recorded a reduction of emissions (CO2, CO and NOx) of about 3,093 tonnes. On the average, increment in exposure to road users and environment of total CO, CO2, and NOx is expected to be 945.25tonnes per annum for the 3-lane option. Fuel consumptions also recorded reduction of 25.7 litres per 1000veh/km for the 3-lane dual carriageway as against the ‘do nothing alternative’ for small cars and also a reduction of 281.52 litres for heavy trucks. Comparing the 3-lane alternative with the overlay option, again fuel consumption also saw a reduction of 266.021litres per 1000veh/km for heavy trucks and 23.22 litres for small cars. The study also showed a strong correlation between average roughness and yearly emission levels in all alternatives. The study revealed that emissions of CO and NOx by each vehicle class compared with the US Environmental Protection Agency’s standards for Tier 0 and Tier1 vehicle groups were beyond the acceptable limits for human health and environmental sustainability. It was revealed that fuel iv consumption is directly linked to average roughness with a strong coefficient of correlation of 0.9987. Finally, the study also showed that timely overlay interventions gave good results on the 3-lane dual carriageway.
A thesis submitted to the Department of Civil Engineering, College of Engineering in partial fulfillment of the requirements for the degree of Master of Science Road and Transportation Engineering.