Contributions to motor vehicle emissions analysis

While motor vehicles are a major source of atmospheric pollutants, their in-use emissions remain inadequately characterized. Remote sensing devices (RSD) have been shown to be efficient tools for measuring CO, HC and NO in on-road vehicle exhaust. This work utilizes RSD data to illuminate new phenomena related to automobile emissions.; Model year averaged RSD data are shown to correlate extremely well with IM240 measurements. IM240 is a loaded-mode dynamometer test used by several states as part of their emissions reduction strategy. The high degree of correlation helps to validate remote sensing as an instrument for IM240 evaluation. Such evaluations of programs in Chicago and Denver indicate an Inspection and Maintenance benefit of less than 10%.; Fleet average on-road emissions have continually decreased over several years of measurement at the same locations in four U.S. cities: Chicago, Denver, Los Angeles and Phoenix. Together with the decrease in overall emissions, the distribution has become even more skewed. Fewer automobiles are responsible for a larger fraction of the decreasing total pollutant emissions. Analysis of the newest model year vehicles year after year at the four locations indicates that successive model years have become lower emitting. It is believed that more stringent government mandated emission standards and continuous improvement in the ability of automobile manufacturers to meet these standards is responsible for the emissions reductions.; Comparison of emissions among the four cities, adjusted for load and model year, indicates that older vehicles in the Los Angeles area have higher CO and lower NO emissions. The fact that California had more stringent NO emission standards and more lenient CO ones compared to the rest of the states suggests, once again, the significant benefits of emission standards and new vehicle emission control technology.