This paper presents key results from an exhaust emission study conducted on over 105 buses in idling condition and selected sample buses from seven fleets in real-world operating conditions in Toledo, OH on the effects of different vehicular parameters on public transport bus emissions. It was observed that for the same amount of time in operation, vehicles in idling mode produced higher average concentrations of carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2) and sulfur dioxide (SO2). Regular engine idling mode and higher engine temperatures were found to reduce vehicular emissions most significantly (up to 30-42%) while performing preventative maintenance reduced emission concentrations by 15-20%. As compared to ultra-low sulfur diesel (ULSD) fuel, use of B20 grade bio-diesel resulted in 159.74 ppm lower CO, 138.3 ppm higher NO, and 8.01 ppm higher NO2 concentrations for 300 series fleet (Bluebird) and 28.4 ppm lower CO concentrations and 2.59 ppm lower NO2 for series 500 fleet (Thomas). These results highlighted that engine technology was a deciding factor affecting the emission behavior of each fleet.
Abstract