Urban air pollution is considered to be a critical environmental and public health issue, with the transportation sector being a major contributor. This study focuses on tailpipe pollutant emissions from light-duty vehicles in real driving conditions. Our principle objective was to identify primary factors that affect the emission rates under different driving styles, fuel grade, engine transmission, and checking/maintenance practices. We observed that emission rates were consistently lower with frequent acceleration and deceleration associated with aggressive driving (AD) compared to relaxed driving (RD) style. This indicates that vehicles driven in town (which are typically driven in a relaxed manner) may require more regular maintenance than vehicles driven on motorways (which are typically driven in an aggressive manner). All pollutant emissions were higher in manual transmission vehicles on both urban roads and motorways than in automatic transmission vehicles. The information generated from this research can help establish framework for pollution mitigation efforts, such as inspection and maintenance programs, and in developing traffic pollution management strategies for national use. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 335-343, 2013 [ABSTRACT FROM AUTHOR]