Doctoral Dissertations

Date of Award

8-2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Civil Engineering

Major Professor

Dr. Arun Chatterjee

Committee Members

Dr. Terry Miller, Dr. Stephen Richards, Dr. Shih-Lung Shaw

Abstract

This research study collected local commercial vehicle data in Knox County, Tennessee from the United States Postal Service and two companies engaged in package pickup and delivery. A second urban commercial vehicle dataset from a wider spectrum of companies in North Carolina was also obtained for comparative analysis. The two datasets are analyzed in a similar manner to develop and compare travel characteristics/parameters commonly used in transportation engineering, such as Daily VMT, Daily Number of Trips, Vehicle Speed, Trip Length, Trip Travel Time and Stop Duration. Statistical tests demonstrate the similarities between certain vehicle classes from the two datasets and four aggregated Vehicle Usage Classes are formed. A second type of analysis is also conducted to develop two sets of input parameters for use in place of the default values in EPA’s MOBILE6 model, which estimates mobile source emissions. Two basic runs use all the developed inputs together and model the commercial vehicle datasets in their entirety. Four additional runs model each Vehicle Usage Class individually through the use of the average speed and starts per day specific to each class. Changes in the resulting emission factors in relation to the default run are discussed and the reasons are determined.

The study concludes that vehicles of different industries can show similarities in travel characteristics, independent of vehicle size and type, depending on the way they are used. Commercial vehicles show higher Annual Mileage Accumulation Rates than the default values, hence showing higher levels and longer terms of usage. Also their VMT and Engine Start distributions by Hour of Day are very different from the default curves, occurring primarily within the two daily peak traffic periods (am and pm). The study finds higher VOC, CO and NOx compared to the default run for USPS vehicles mainly due to their much lower than default average speed. Also higher VOC and CO are found for both gas and diesel Package PUD vehicles due to lower than default average speed (CO for gas and both VOC and CO for diesels) and higher than default starts per day (VOC for gas vehicles).

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