School buses, Biodiesel, MOBILE6.2, Emissions


Orange County, FL has been experiencing ozone concentrations in the past several years which in some cases exceeded the national and state standards. The high concentration of ground level ozone can cause a variety of health problems including chest pain, coughing, throat irritation, and congestion or it can worsen bronchitis, emphysema, and asthma. Other effects include reduction of agricultural crop and commercial forest yields, lower growth and survivability of tree seedlings, and higher susceptibility of plant to diseases, pests and other stresses such as harsh weather. The ozone generation rate is directly related to the ambient concentration of nitrogen oxides (NOx) and volatile organic carbons (VOCs). These two air pollutants, mostly produced from combustion of fossil fuels, react with oxygen to form ozone in presence of sunlight. In urban areas, ozone generation rate can be decreased by reduction of ozone precursors, NOx and VOCs. The Air Quality Research group of University of Central Florida proposed that one of the emission reduction strategies be for school bus fleets in the area. School buses were chosen because of their important impact on ambient air quality in general and on student health in particular. There were about 473,000 school buses in the 2004-05 school year nationwide which traveled for a total mileage of about 4 billion miles in that year. Orange County Public School (OCPS) system owns about 1400 school buses which traveled about 17 million miles in 2005-06 school year, serving 71000 students. The use of diesel fuels, Ultra Low Sulfur Diesel (ULSD, diesel fuel containing 15ppm sulfur) and Biodiesel (B20, a mixture of 20% biodiesel and 80% ULSD), were chosen as the first proposed action to be studied. Also the effects of transportation parameters, average speed and idling time on fleet emissions were selected to be reviewed. This report reviews the fuel option and transportation parameters, effects on school bus fleet emissions and it does a comparison analysis in order to show advantages and disadvantages of each fuel. The Conventional Diesel (CD) and ULSD emissions were estimated by using MOBILE6.2 model, and effects of B20 on emissions were derived from published studies. It was found that using B20 or ULSD can reduce the emissions significantly for the most of major pollutants but in the case of NOx, the percentage changes is not certain yet and more investigation is required. Emissions vary for different average speeds and 27 miles per hour can be defined as the optimum average speed. Also reduction of idling time is an excellent control option for decreasing emissions, and should be considered for OCPS.


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Graduation Date





Cooper, C. David


Master of Science (M.S.)


College of Engineering and Computer Science


Civil and Environmental Engineering

Degree Program

Environmental Engineering








Release Date

September 2007

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)