Transactions for Precise Multi-Vehicle Maneuver Planning: Blockchain Applications for Earned Trust, Non-Binary Fault and System Safety

Karl Wunderlich, PhD, Director, Noblis Autonomous Systems Research Center

Autonomous vehicles (AVs) are often portrayed charting an inevitable pathway towards transformative roadway system efficiency and safety. However, current AVs are designed to work within (and limited by) a system of laws, liabilities, licensing, taxation, traffic controls 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 those expected 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?

As one possible answer to this question, Noblis has proposed a broader ecosystem that includes transactions and trust management built on a decentralized blockchain solution. Vehicles engaged in collective maneuver planning require some way to share intent as well as earned trust. A trust report for all vehicles would be managed externally by a consortium of entities facilitating the ecosystem’s transactions. We specifically use distributed ledger (or blockchain) technology because it is particularly well suited to the creation and enforcement of smart micro-contracts among machines. Videos from our Noblis Autonomous Systems Laboratory show autonomous rovers self-organizing collective maneuver plans by building earned trust over a sequence of similar, episodic interactions. The resulting trust framework optimizes safety and efficiency for all participants.

Moreover, a critical element of creating maneuver transactions is the generation of value when vehicles negotiate for priority. To receive priority in a shared system, a vehicle must out-bid the other vehicles competing for that space. The resulting value can be distributed among all the entities in the ecosystem so that operational efficiency and equitable ecosystem financing align in ways that are simply not possible in a human-centric system.

Distribution of the resulting value within the ecosystem could consider all parties facilitating aspects of the transaction, including yielding priority, providing and maintaining the maneuver space, providing maneuver and sensor verification reports, providing reliable position and timing data, managing trust reports and recording transactions. Noblis is currently conducting research to examine the viability of such a system and its potential to address long-standing issues in equitable roadway system financial sustainability. For more on this topic, please see this recent publication.

We can extend this framework even further to consider fundamental considerations of liability. Note that when a collective maneuver plan cannot be completely executed, the result is that the smart contract among the participating vehicles is broken. This may be because the vehicle proposed a maneuver that it could not complete precisely within the dynamic space allocated within the plan. Or perhaps faulty sensors on one vehicle resulted in the creation of an inaccurate collective obstacle map. Even if no collision occurred because of one or more of these failures, a comparison between the detailed maneuver plan and the executed vehicle trajectories allows the system to record which vehicles deviated from plans (resulting in reduced trust) and which adhered to them (resulting in increased trust). Plan deviation informs fault – and therefore liability. Costs associated with a failed maneuver plan can be allocated to those vehicles found to be at fault, providing an incentive for vehicles to only propose safe and predictable maneuver trajectories and provide error-free sensor reports.

While a nationwide roadway of AVs may seem a long way off, a system of coordination and trust will be essential to its development. Noblis’ framework for managing trust, liability and ad hoc coordination through distributed ledger transactions provides an innovative vision for one way such a system could be managed.

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