Bus technology meta-analysis

This paper analyzes data obtained from international studies that compared natural gas, diesel, and hybrid technologies for buses to determine differences in particulate matter (PM₁₀), nitrogen oxides (NO _x), nonmethane hydrocarbon (NMHC), carbon monoxide (CO), greenhouse gas, and air toxic emissions. The results presented here are for 90-passenger 12-m buses. Two types of comparisons were made: technology and fuel. The comparison revealed that buses using ultra-low-sulfur diesel (ULSD) with diesel particulate filters (DPF) and buses using compressed natural gas (CNG) with oxidation catalysts (OC) had the lowest emissions of PM₁₀ and CO; CNG with OC had lower NO_x and greenhouse gases emissions, while ULSD with DPF had lower NMHC emissions. Posttreatment technologies are presented as a low-cost option to reduce emissions. Hybrid diesel buses were found to be the technology that has the lowest emissions for most of the studied pollutants.