Driving style extremes and potential vehicle emission effects

Chassis dynamometer driving cycles designed to quantify vehicle emissions often miss the extremes in driver behaviour. The vehicle emissions measured during these driving cycles are used for modelling and policy purposes. To better understand the impact of omitting such extremes, two drivers were asked to follow a set of behavioural rules to replicate ‘aggressive’ and ‘passive’ driving styles along a real-world route in Southampton, UK. The test route included a wide range of traffic conditions that could be expected on urban roads. The resulting driving profiles were compared to a number of legislative driving cycles – this indicated that aggressive driving was poorly addressed by these cycles. When replicated on a chassis dynamometer, the aggressive profile produced carbon monoxide, oxides of nitrogen and carbon dioxide emission rates of 2·68, 0·853 and 183·6 g/km, respectively, whereas the passive profile produced only 0·064, 0·011 and 124·4 g/km, respectively. Non-inclusion of aggressive driving styles in legislative driving cycles will mean that driving events that lead to disproportionately high emissions are not addressed by legislation designed to improve overall vehicle emissions control performance (e.g. Euro standards). In addition, a proportion of vehicle emissions will be missed from the modelling process which may have implications for local authorities declaring Air Quality Management Areas.