The primary intent of this report is to provide a comprehensive and concise overview of the apparent safety issues presented to pedestrians and pedalcyclists by the operation of quiet vehicles on roadways. The report provides background information to establish how this issue became the focus of safety research in the United States and elsewhere. It presents the findings of a literature review of notable major research and a review of related pending and established regulations. The report also describes implemented and proposed countermeasure methods in addition to opportunities for future potential research to address knowledge gaps and improve overall understanding of the issues.