Analysis of a Remote Sensing Clean Screen Program in Arizona

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This report analyzes the effectiveness of using remote sensing data to “clean screen” vehicles for exemption from their upcoming emissions inspection and maintenance (I/M) test. By exempting the cleanest vehicles from I/M testing, limited resources can be concentrated on identifying and repairing vehicles with the highest emissions. We apply the methodology used in the Colorado clean screen pilot program to 18 months of remote sensing and IM240 data from Arizona. We analyze a random sample of vehicles given the full IM240 test, as well as all vehicles tested during this period in Arizona. Our primary conclusions are that:

1)  less than one-third of the vehicles in the Arizona I/M program were measured by remote sensing over an entire year of measurement;

2)  the clean screen methodology used in Colorado is slightly less effective in identifying the cleanest vehicles in the Arizona fleet;

3)  exempting the newest model years of cars is more effective than using a remote sensing clean screen; however, because much of the excess NOx emissions from light duty trucks comes from relatively new model years, states should carefully consider whether to exempt recent model year trucks from I/M testing.

This report describes these results, and examines other aspects of applying a clean screen program in Arizona. 

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