From Latency to Value of Information: A Review of Timeliness Metrics for Safe Transportation Systems in the 6G Era

Traffic safety in the 6G era will depend on vehicles exchanging information that is not only timely but also accurate and contextually relevant for cooperative awareness, collective perception, and automated driving. Classic performance metrics such as latency and reliability describe communication behavior, but do not capture how shared data supports situational awareness. Timeliness- and semantic-oriented metrics including Age of Information (AoI) and Value of Information (VoI) provide deeper insight into freshness and usefulness, yet open questions remain on how to assess performance across increasingly complex vehicular functions. This paper reviews the state of the art in timeliness metrics for vehicular networks, surveys the corresponding standardization landscape, and examines the applicability and limitations of AoI-based and related metrics. It highlights persistent gaps in evaluating cooperative and automated driving services and outlines directions toward goal-oriented performance assessment suited to safety-critical 6G transportation systems.