By Karl Wunderlich
Autonomous vehicles (AVs) are often portrayed charting an inevitable pathway towards transformative roadway system efficiency and safety. However, current AVs are designed to operate within (and limited by) a legacy system of laws, liabilities, licensing, taxation, control systems and normative behaviors built on the assumption that vehicles will have human drivers.
In other words, even if an AV may be able to go faster, corner more tightly or safely maneuver around obstacles with a margin of error much smaller than human drivers, they must remain restricted, for now, to maneuvers expected from a human-driven vehicle for two key reasons. First, deviation from legacy norms would disrupt nearby human drivers; second, current AVs are simply not ready to self-organize outside our legacy system. By default, then, in the near-term we must rely on the speed limits, lane lines, stop signals and other rules of the road we have developed in a broadly ad hoc fashion in 100+ years of human-driven automobility. But once we have millions of AVs in motion at the same time and AVs are the norm not the exception, are the legacy forms of general self-organization that compensate for the limitations of human drivers still practical, or even desirable?
First, let’s consider a collection of AVs preparing to traverse a four-way intersection that has been stripped of all legacy markings and controls. The AVs cannot safely traverse such an intersection without deconflicting their planned maneuvers. Deconfliction is impossible without establishing priority. Two vehicles (AVs or human-driven) cannot occupy the same space at the same time. If two vehicles do attempt to occupy the same space at the same time, the result is collision. Therefore, some form of priority access to the dynamic space is required. The vehicle granted priority can simply maintain its current path plan through the intersection. The vehicle that yields priority must replan and must reject any new path that conflicts with the path plan of the vehicle with priority.