Relative influence of acceleration level and speed on emissions, under actual driving conditions

This paper assesses the impact of speed and acceleration on exhaust pollutant emissions. Kinematic sequences were randomly selected from actual driving recordings in order to constitute a representative set of driving conditions. For each sequence average speed and positive acceleration were calculated. Istantaneous and integrated pollutant emissions were calculated using an emission model based on istantaneous emission measurements. Emissions of CO, CO2, HC and NOx were analysed for diesel, conventionaland catalyst vehicles , and finally the whole French car fleet. A siginificant influence of speed on emissions was observed. The acceleration impact was relatively low, and much lower than the influence observed when considering the istantaneous values, except forthe catalyst vehicles,which showed the strongest dependence on acceleration. Tis low impact on emissions shows that the potential emissions reduction through the improvement of traffic conditions, could be relatively limited.