Can we estimate PM-emission reductions from speed management policies?

Abstract

Speed reduction measures are commonly introduced to increase traffic safety. Recently many urban streets or entire districts were converted into 30 km/h zones and in many European countries the maximum speed of lorries is under discussion. Reducing the maximum speed is seen as beneficial to the environment because of reduced fuel consumption and lower emissions. These claims however are often unsubstantiated. We calculated emissions for specific vehicles with a microscopic model using real-life driving cycles and compared the results with those from MEET. Although emissions of most classic pollutants should not be expected to rise or fall dramatically, the conclusion for PM could be different. The effects of speed reduction schemes on PM emissions from trucks on highways are ambiguous, but detailed modelling results indicate that the PM exhaust from diesel passenger cars may show a significant decrease in urban areas converted to 30 km/h zones.