Increasing vehicle fuel economy and the likely adoption of alternative fuel vehicles in the coming decades dim prospects for continued reliance on gasoline and diesel excise taxes to fund highway and bridge maintenance, expansion, and completion. Road use charges based on vehicle miles of travel (VMT fees) are viewed by many as a promising replacement for fuel taxes; their revenue yield would be unaffected by fuel economy or fuel type, the fees could be structured to help address additional transportation goals (e.g., reducing recurrent traffic congestion, harmful emissions, and excessive road wear), the system could provide detailed travel data to support improved transportation planning and operations, and the in-vehicle metering equipment could serve as a platform for additional driver services. Yet transitioning from fuel taxes to VMT fees would be a complex undertaking, with many technical, institutional, and political uncertainties to be resolved. To prepare for such a transition, it could be helpful to conduct an extensive set of system trials. The goal in this study is to explore options for scoping and organizing such trials. Policymakers interested in staging trials with the aim of examining and refining concepts for implementing a VMT-fee system would need to consider such questions as: how large the trials should be and how long they should last; how much it would cost to conduct the trials; whether the trials should be conducted in all states or just a few; whether the trials should involve trucks, passenger cars, or both; what types of pricing policies the trials should examine; what technical, institutional, and user acceptance issues should be probed; and who should oversee, manage, and conduct the trials. To gain insight into such questions and identify the factors likely to influence the success of trials, the research team solicited the thoughts and perspectives of representative stakeholders and subject matter experts through an extensive set of guided interviews followed by a one-day workshop. Based on participant responses and supporting research, it is possible to outline several approaches for funding, organizing, structuring, managing, and conducting a set of VMT-fee system trials. The trials could be complemented by parallel efforts in the areas of planning and policy guidance, analytic studies, technical research and development, and public education and outreach.