Aggregated emission models are now used with efficiency to carry out inventories of pollution on national or regional scales, but they are not accurate enough to be used on a more limited one. That's why we are now trying to develop a reliable model to appraise impact of street design on emissions and thus optimise traffic management and its consequences on air quality. Models are used to predict emissions for cycles performing various driving conditions. Accuracy is assessed in comparing computed results with measurements done on dynamometer chassis. The first tested model is an instantaneous model based on emission matrix. It describes the instantaneous emission according to the corresponding instantaneous driving parameters. This model is compared to the average speed model. Results of both models show the difficulties in recovering measured values for several cycles. A description of emissive behaviour of each vehicle is required to improve accuracy of emission assessments. The instantaneous emission records exhibit periods of high emission level that are long in regard to kinematic patterns. To enhance the instantaneous emission approach, a model describing these high emission sequences is developed for catalyst cars. A probabilistic approach is used to characterise occurrences of these sequences for each vehicle. Results compared to measurements are somewhat disappointing. Improvement of instantaneous emission measurements should lead to change in the simplistic hypotheses of this model and improve quality of emission forecasts according to driving kinematics.
