CHARACTERIZING THE EFFECTS OF DRIVER VARIABILITY ON REAL-WORLD VEHICLE EMISSIONS

Recent studies on real-world automobile emissions measurements have no t adequately addressed the question of whether driving style affects e mission levels. In this study, we hypothesized that given the same exp erimental conditions and a random selection of drivers, the variabilit y associated with individual driving styles (e.g. intensity or duratio n of acceleration events) would produce statistically significant diff erences in measured emissions. To test this driver variability hypothe sis, we conducted a field study on 24 drivers in a single vehicle on a specified route under low traffic conditions using on-board exhaust e mission and engine operating data analyzers and tested for statistical ly significant differences in CO and NOx emissions between drivers. Ou r data show significant (95% level) variations in carbon monoxide (GO) and oxides of nitrogen (NOx) emissions among the 24 drivers under dri ving conditions where we have controlled for driving route, traffic de nsity and vehicle type. Since the ANOVA tests showed significant diffe rences in emissions between drivers but the frequency of driving modes were very similar, this suggests that the intensity of vehicle operat ion within a give mode, not the modal frequency, explains the emission s variability between drivers. (C) 1998 Elsevier Science Ltd. All righ ts reserved.