Research Projects

Evaporative emission control systems have been required on light-duty vehicles beginning with the 1970 model year and on heavy-duty vehicles beginning with the 1973 model year. Due to the large number of vehicles operating in California, (roughly 10.7 million light-duty and 1.9 million heavy-duty vehicles) the evaporative emissions from the uncontrolled vehicles may be significant. This study was structured to assess the technical and economic feasibility of retrofitting or otherwise modifying these evaporative uncontrolled, pre-1970 light and heavy-duty vehicles with devices, systems, and concepts similar to those used on the production 1970 to 1973 model light-duty vehicles. The study evaluates and cost-estimates fuel tank modifications, carburetor modifications, and combinations of the two basic modifications. Effectiveness measures in terms of evaporative emissions controlled are calculated for the feasible retrofit systems as a function of vehicle model year, air basin, and total State. The cost effectiveness of various retrofit approaches is calculated and discussed.