On-road measurements of single vehicle pollutant emissions, speed and acceleration for large fleets of vehicles in different traffic environments

The on-road CO and HC emissions from 10 000 cars in four different traffic environments, typical of urban driving, were measured by a remote sensing technique in Linköping and Gothenburg, Sweden. In parallel, the speed and acceleration of each car were registered. Further, fuel consumption measurements were made on-board a small sample of cars repeatedly driving by the measurement sites. The study aimed at investigating how laboratory emission data conform to real-world conditions. The on-road emission and fuel data were compared to modal chassis dynamometer data for 60 non-catalyst and nine catalyst cars. Emissions from catalyst cars, in particular CO, were considerably higher on the road than what could be derived from dynamometer data, even after considering effects of catalyst ageing and cold starts, whereas the agreement between on-road and dynamometer data was considerably better for non-catalyst cars. The discrepancies were mainly attributed to a small fraction of ‘high-emitting’ cars with malfunctioning catalysts.