| The primary purpose of this dissertation is to develop methodologies for on-board vehicle activity and emissions data collection and data screening. Eight gasoline fueled light-duty vehicles and four drivers were tested, resulting in a total of 824 one-way runs representing approximately 1,000 vehicle-hours and 2,020 vehicle-miles of simultaneous second-by-second vehicle activity and emissions data. Exploratory analysis of these data revealed that emissions are different under different vehicle operation conditions. A priori modal definitions were developed based upon vehicle speed and acceleration. It was found that modal definitions yield statistically significantly different emission rates for idle, acceleration, cruise, and deceleration. The average emission rate on a mass per time basis for acceleration was found to be typically a factor of five greater than the idle emission rate for HC and CO2, and a factor of ten or more for NO and CO. A key implication of this finding is that methods for reducing real-world on-road emissions should involve measures that reduce the frequency and duration of episodic events, such as high accelerations, that lead to short periods of high emissions.; A secondary, but equally important, purpose was to utilize vehicle activity and emissions data collected to tackle real-world problems related to vehicle emissions. One of these problems is to investigate emissions hotspots along roadways. Methods were developed to identify hotspot locations and applied to two example case studies to illustrate the types of insights obtained from this analysis. For the example case studies, emissions associated with a single signalized intersection contributed substantially to total emissions for a particular corridor.; The sensitivity of different emissions factor estimation methods (i.e., distance-based, time-based, and fuel-based) was investigated with respect to vehicle operation modes. It was found that time- and distance-based emission factor estimation methods are sensitive to different vehicle operation modes. For fuel-based method NO emission, are sensitive to mode, however, CO and HC emissions are less sensitive to mode.; The effect of changes in signal timing and coordination on vehicle emissions was also investigated. It was found that differences in emissions were highly associated with differences in quantitative measures of traffic flow such as average speed, average control delay, and average number of stops per mile. (Abstract shortened by UMI.)... |
