The significance of vehicle technology and driver behaviour in determining road vehicle exhaust emission rates

Abstract

This research utilises data from instrumented vehicles and road side remote sensing in an urban environment to explore the relationships between exhaust tail pipe emissions, vehicle technology, and driver behaviour. An investigation is carried out into the nature of variability that exists in the driving behaviour of a sample of drivers, and the influence of such variability on fuel consumption and the emission rates of exhaust pollutants. Analysis of data from remote sensing reveals that emissions from petrol cars (CO, HC, NO, PM) are all observed to display a statistically significant reduction with the introduction of each successive Euro emissions standard from Euro 1 onwards. However, Euro 2 diesel cars are observed to emit statistically higher rates of NO than either Euro 1 or Euro 3 standard diesel cars. When the New European Driving Cycle is synthesised from remote sensing data and compared with type approval data published by the UK Vehicle Certification Agency, mean CO emissions from petrol cars ≤3 years old measured using remote sensing are found to be 1.3 times higher than published original type approval test values; this factor increases to 2.2 for cars 4 – 8 years old, and 6.4 for cars 9 – 12 years old. The corresponding factors for diesel cars are 1.1, 1.4, and 1.2 respectively. This thesis has made an original contribution to the field in two main areas; firstly by quantifying the ‘real-world’ emission rates for a sample of the UK vehicle fleet in an urban area, and demonstrating the statistically significant differences in emission rates between groups of vehicles; and secondly, by proposing a feasible method to move towards reconciling essentially instantaneous road side measurements of exhaust emissions obtained from remote sensing, with laboratory based measurements taken over a legislated driving cycle as part of the new vehicle type approval process.