Cohorts and groups for safe and efficient autonomous driving on highways

We introduce constructs aimed at reconciling safety and efficiency for ad hoc highway-centric clusters of autonomous vehicles. The cohort construct is an ad hoc variant of the platoon construct. We show how to enforce safe inter-vehicle spacing in cohorts despite inaccurate vehicle space-time coordinates and failing telemetry capabilities, via neighbor-to-neighbor beaconing based on short range unidirectional communications. Worst-case analytical results are established for safe spacing bounds. A classical spacing algorithm is revisited, and proofs of usability in a discrete time beaconing model are given. Along with the group construct, which is based on prefixing usage of sensing-based solutions with omnidirectional inter-vehicular communications, we present a categorization of safety-critical scenarios. We discuss the benefits resulting from prefixing vehicle maneuvers with vehicle role assignments in safety-critical scenarios.