This report examines the approaches that are being used by a variety of institutions to regulate rapidly emerging technologies in transportation. Several case studies were examined to determine if there are relevant criteria and situational contexts that determine an agency’s choice of either voluntary standards (industry self-regulation) or governmental rulemaking. From this case study analysis, the research team identified the following: • “Voluntary” and “mandatory” models of rulemaking are not binary choices; rather they are different points along a continuum. • The federal government, including the Department of Transportation, have developed regulatory tools that rely on both voluntary and mandatory approaches to accommodate innovation. • Alternative approaches of rulemaking utilized by other agencies, such as a cooperative mixed-model, may be useful for future regulation of automated vehicles.