We present the cohort and the group constructs which are aimed at reconciling safety and efficiency for intelligent vehicular networks on roads and highways, and show how platoons and vehicular ad hoc networks can be structured as cohorts and groups. Fundamental implications of safety requirements are reviewed. A rationale for on-board systems based on diversified functional redundancy is developed, illustrated with a proposal for neighbor-to-neighbor periodic beaconing based on short range unidirectional communications meant to withstand telemetry failures. Worst-case analytical results are given for safe inter-vehicle spacing in cohorts despite inaccurate vehicle space-time coordinates and failing telemetry capabilities. The group construct is based on prefixing usage of sensing-based solutions with omnidirectional communications. Benefits resulting from prefixing vehicle maneuvers with vehicle role assignments are illustrated with the on-ramp-merging safety-critical scenario.