First, the low traffic counts recorded may indicate occurrence of traffic jam with idling vehicles emitting pollutants, leading to higher pollutant emissions.Second, the turbulences caused by driving-by vehicles may actually enhance dispersion of pollutants, resulting in negligible increase of CO and even decreasing PM levels at all locations with traffic. The significant contribution from traffic may only be quantified at locations such as but stops and interactions where emissions from so many passing-by vehicles overrode the turbulence effect. Third,