The effects of traffic flow conditions on the pollutants emissions: a driving simulator study

In the last 20 years the attention of international organizations towards air pollution has been improved, leading to definition of laws and regulations. In order to evaluate strategies and policies, forecasting tools have been adopted by institutions. Mainly, two groups of emission models are available: the former is represented by the static or “standard” models, in which the amount of pollutant is computed as a function of average parameters; the latter is represented by the dynamic models, where the amount of pollutant is computed as a function of instantaneous parameter, such as instantaneous speed or acceleration. The well-known traffic increase of the recent years has significantly changed the actual flow conditions, producing a strong rise of interferences. As this facet affects the operating condition of each vehicle, the use of a standard emission models at high traffic interference can lead to some inaccuracies. In such cases, instantaneous emission models introduce deeper capabilities; essentially, the pollutant prediction is directly tied to the engine vehicle operation point in real-like traffic condition. However, this approach requires a large amount of input data (i.e. video recordings or remote sensing analysis), which are not always available. In order to overtake such a difficulty, the present study is based on an integrated simulation tool. Emissions from road traffic are simulated through a dynamic model, whose input data are obtained by the output of virtual reality simulation. Indeed, the analysis took advantage of the experiments carried out in the vehicle virtual reality laboratory: on typical highway geometry, three different flow conditions have been simulated. Investigations have highlighted the dependence of emission level and fuel consumption on drivers’ behavior. The comparison between a gasoline and a diesel compact passenger car in terms of pollutant emissions and fuel consumption has been also reported. In order to assess the differences between static and instantaneous emission models, a comparative analysis has been carried out.