We examine longitudinal and lateral safety-critical scenarios as they arise in VANETs, in the presence of concurrency and unreliable inter-vehicular communications. The Fast Distributed Agreement (FastDA) problem, as well as solutions to the longitudinal and the lateral instantiations of FastDA, are examined and informally specified. Analytical expressions of worst-case time bounds for reaching agreement are provided. We verify that stringent safety requirements are met through realistic examples drawn from various safety-critical scenarios.