COLD START EMISSIONS OF TRAFFIC

CO, HC, NOx, particulate emissions and fueld consumption were measured on a chassis dynamometer for both hot and cold start. Three urban driving cycles were used, two ECE15 cycles for tuned and as received vehicles and one representative of the actual driving patterns. 51 cars (gasoline and diesel engines) were tested using this method. From these measurements and others made in Europe we are able to know the influence of ambient temperature on cold start emission rates and fuel consumption of passenger cars. In addition the actual operating conditions of 35 private cars operated normally by their owners were recorded in winter and summer all over France, over a total distance of 23000 km. The great number of short trips (40% less than 2 km) shows the importance of cold start. The modelling allows us to know the mileage percentage according to cooling water and ambient temperature. So we can calculate the cold mileage percentage according to trip length (the average percentage is 27% in France). These results allow us to model traffic cold start emissions for different national and local situation as regards the ambient temperature and the actual driving patterns. The additional emissions can be very high for some pollutants such as CO (30% in France) or VOC (46%). © 1990.