On-Road Remote Sensing of Automobile Emissions in the Phoenix Area: Year 1

EXECUTIVE SUMMARY The University of Denver conducted a four-day remote sensing study in the Phoenix, AZ area in the fall of 1998. The remote sensor used in this study is capable of measuring the ratios of CO, HC, and NO to CO 2 in motor vehicle exhaust. From these ratios, we calculate the percent concentrations of CO, CO 2 , HC and NO in motor vehicle exhaust which would be observed by a tailpipe probe, corrected for water and any excess oxygen not involved in combustion. The system used in this study was also configured to determine the speed and acceleration of the vehicle, and was accompanied by a video system to record the license plate of the vehicle. A database was compiled containing 17,759 records for which the State of Arizona provided make and model year information. All of these records contained valid measurements for at least CO and CO 2 , and 11,897 contained measurements for HC and NO. The mean percent CO, HC, and NO were determined to be 0.28%, 0.019%, and 0.036%, respectively. These values are amongst the lowest we have observed for a statistically significant fleet, and are considerably lower than those for fleets previously measured in the Chicago area. The fleet emissions measured in this study exhibit a gamma distribution, with the dirtiest 10% of the fleet responsible for 71%, 66%, and 56% of the CO, HC, and NO emissions, respectively. The majority of vehicles (81%) at this location were measured once. The remaining 19% of the measurements were of vehicles measured at least twice. By removing all of the repeat measurements from the database and allowing each vehicle to appear only once, we have shown that these repeat measurements are not skewing the results and that the full database is statistically representative of the actual fleet at the measurement site. This was the first year of a five-year continuing study to characterize motor vehicle emissions and deterioration in the Phoenix area. However, because of the driving mode at this site a new location similar to the Denver, Chicago and L.A. Basin sites has been selected for 1999.