An investigation into the effect of road gradient and driving style on [formula omitted] emissions from a diesel vehicle driven on urban roads

Abstract

This study explores the influence of different driving styles and road gradient profiles on NOX emissions in a diesel passenger vehicle on urban driving. Driving dynamics parameters were correlated with cumulative NOX emissions measured during on-road driving on urban roads. In this work, the vehicle was driven on two different urban routes, one with mostly hilly roads and the other with predominately flat roads to assess the effect of road gradient on NOX emissions. Each route was driven six times, the first drive on each route was driven very timidly, each subsequent drive systematically became more aggressive with the sixth drive being very aggressive. From the vehicle speed and road gradient data, the instantaneous vehicle energy was estimated and correlated against the instantaneous NOX emission. In order to investigate for monotonic relationships, Spearmans rank correlation coefficient was used to investigate potential correlations between NOX emissions and driving parameters. A strong positive correlation was observed between instantaneous NOX emissions and instantaneous vehicle energy irrespective of the driving behaviour. The correlation of driving dynamics parameters with NOX emissions also showed a similar trend indicating that driving aggressiveness and vehicle NOX emissions have a strong relationship. Also there is evidence that the influence of road gradient on NOX emissions decreases with an increase in driving aggressiveness.