<div class="htmlview paragraph">Voluntary RFG opt-in and use of reduced-RVP gasoline are two fuel options being considered in several ozone nonattainment areas. This paper describes methods for evaluating the relative benefits of these two options, with specific application in the Southeast Michigan area. Currently, the most defensible approach for estimating relative emissions reduction benefits of gasoline modifications utilizes a hybrid of two EPA models: MOBILE5a and the Complex Model. By employing appropriate fuel compositions, this hybrid approach showed that reduced-RVP gasoline was nearly as effective as RFG in reducing total VOC emissions in Southeast Michigan-both near-term and long-term. With both gasoline options, most of the VOC benefit arises from lower nonexhaust emissions, caused by reduced RVP levels. When considering all relevant issues-including ozone precursor emissions, reactivity, toxics emissions, fuel economy, and economics-reduced-RVP gasoline appears to be a highly attractive alternative to RFG in Southeast Michigan. Similar results would be expected in other locations, although a careful assessment is necessary to quantify and compare the benefits of these two fuel options in each case.</div>