Abstract: The technical description relates to perimeters for vehicles. Specific examples relate to vehicle perimeters established by unmanned aerial vehicles (UAVs), such as autonomous drones, for a variety of vehicle types, including manually-driven, partially autonomous, and fully autonomous vehicles. Perimeter devices, vehicles, including autonomous vehicles and human-controlled vehicles, UAVs, and related systems and methods are described. Perimeter devices respond to triggering events, such as vehicle-immobilizing events, GPS-based events, and environment-based events, to establish a perimeter adjacent a vehicle such that observers can visually detect the presence of a signal member, such as a warning triangle having a reflective surface. An example vehicle includes a tractor unit, a trailer connected to the tractor unit, a storage enclosure associated with the tractor unit, and a plurality of perimeter devices disposed in the chamber.