A series of field and laboratory-based tests was undertaken to examine the effectiveness of the University of Denver's FEAT (Fuel Economy Automobile Test) system for the remote measurement of carbon monoxide and hydrocarbon emissions. The evaluation was carried out primarily to determine the system's effectiveness in identifying poorly maintained and high emitting vehicles in a stream of traffic, and a number of studies also considered its accuracy and repeatability. Comparisons of individual remote sensing results with other standard test methods (idle and dynamometer drive cycles) showed little overall agreement. Other tests, however, indicated some consistency of instantaneous results: two remote sensing systems in close proximity gave very similar readings and remote sensing data agreed well with conventional measurements under controlled laboratory conditions. It was seen, therefore, that the system was able to provide a reasonably accurate measurement of the exhaust emissions from a vehicle driven through its beam. The lack of a more general link between that measurement and the vehicle's average emissions as determined by standard test methods was considered largely to result from the inhomogeneity of the emission rates of each vehicle, combined with differences between vehicles. Depending on their precise operating conditions, all vehicles can produce low or high rates of emission. In normal use, the remote system provides only a single instantaneous result that depends as much on how the vehicle is driven through the sensor beam as on its overall emission characteristics. (A)

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