RELATIVE INFLUENCE OF ACCELERATION 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. Instantaneous and integrated pollutant emissions were calculated using an emission model, based on instantaneous emission measurements. Emissions of CO, CO2, HC and NOx were analysed for diesel, conventional and catalyst vehicles, and finally the whole French car fleet. A significant influence of speed on emissions was observed. The acceleration impact was relatively low, and much lower than the influence observed when considering instantaneous values, except for the catalyst vehicles, which showed the strongest dependence on acceleration. This low impact on emissions shows that the potential emissions reduction through the improvement of traffic conditions could be relatively limited.