%0 Report
%A Thomas P Wenzel
%D 2000
%G eng
%T Evaluation of the Effectiveness of Alternative Fast Pass, Fast Fail, and Retest Algorithms in the Phoenix IM147 Program
%2 LBNL-48006
%8 10/2000
%X <p>This report compares the current method of quickly identifying passing and failing vehicles in<br />the Phoenix IM147 program (“the Sierra method”) with an alternative method developed by the<br />Arizona Department of Environmental Quality (“the DEQ method”). There are several<br />limitations with the database of over 30,000 vehicles provided to us to make the comparison;<br />therefore our results should be considered estimates of the relative effectiveness of the two<br />methods.<br />The DEQ method results in a slightly lower failure rate, and a slightly longer average test time,<br />than the Sierra method, when applied to all vehicles that would complete testing under the DEQ<br />method. To estimate the number of false passes and failures, and the fraction of total excess<br />emissions identified under each method, we use a subset of 1,775 vehicles for which a full<br />IM147 test (three full traces) is available. The DEQ method results in a much lower false fail<br />rate, and identification of more excess CO emissions, than the Sierra method when applied to<br />this subset of vehicles. On the other hand, the Sierra method results in a slightly lower false pass<br />rate, identification of more excess HC and NOx emissions, and a shorter test time than the DEQ<br />method. The relative effectiveness of each method is consistent whether the cut points currently<br />in use in the Phoenix program, or more stringent cut points developed by EEA, are applied.</p>