RELATIVE INFLUENCE OF ACCELERATION AND SPEED ON EMISSIONS UNDER ACTUAL DRIVING CONDITIONS

This paper assesses the impact of speed and acceleration on exhaust po llutant emissions. Kinematic sequences were randomly selected from act ual driving recordings in order to constitute a representative set of driving conditions. For each sequence, average speed and positive acce leration were calculated. Instantaneous and integrated pollutant emiss ions were calculated using an emission model, based on instantaneous e mission measurements. Emissions of CO, CO2, HC and NOx were analysed f or diesel, conventional and catalyst vehicles, and finally the whole F rench car fleet. A significant influence of speed on emissions was obs erved. 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 ac celeration. This low impact on emissions shows that the potential emis sions reduction through the improvement of traffic conditions, could b e relatively limited.