Summary and Analysis of 2000-2015 Model Year IUVP Evaporative and Refueling Emission Data

As part of an effort to shift focus from the emissions performance of pre-production prototypes in certification to the emissions performance of in-use vehicles, the US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) instituted the “CAP 2000” program. As part of that program, manufacturers are required to retrieve customer-operated in-use vehicles and test their emissions. The EPA and CARB rules contain specific sample size and mileage criteria. The program has been in place for over 15 model years. This paper examines the in-use performance results for 3115 refueling tests, 3844 hot soak+2-day diurnal evaporative emission tests covering five sets of regulatory emission standards, and evaluates several related regulatory issues such as in-use durability and the effectiveness of evaporative on-board diagnostic (OBD) systems. The in-use verification program (IUVP) test results show very high pass rates (95%+) for refueling and evaporative emission tests (except partial zero emission vehicles (PZEV)) and average compliance levels well below the applicable emission standard for odometer readings ranging from 10,000 to 130, 000 miles. PZEV evaporative pass rates were about 91 percent. There was no statistical relationship found between odometer mileage and emission rates. OBD systems performed well in not setting a diagnostic trouble code (DTC) when the vehicle passed the evaporative and refueling emission standards but were not as effective in identifying failures.