The 3GPP V2X resource allocation framework defines two entity classes -- the base station and the vehicle UE -- and four modes across LTE and NR generations. We demonstrate that this binary taxonomy is structurally incomplete. Base station-led scheduling saturates at high-density traffic nodes, producing latency-tail failures that persist even when mean packet delivery ratios approach the service-class target. UE autonomy is categorically incapable of pre-emergence warning for occluded traffic participants and insufficient for large-scope cascading environmental hazards. We propose Mode 0, a new 3GPP V2X category whose defining entity is the Roadside Computing Unit (RCU) -- an infrastructure ensemble integrating elevated sensing (Seeing), sidelink communication (Speaking), and local computational evaluation (Thinking), owned by traffic management authorities. Mode 0 defines a subfamily spectrum from Mode 0a (all-passive UEs, the guaranteed minimum) through Mode 0c (all-active UEs, the optimal target). Convergent deployment evidence from Chinese national standards (DB11/T 2329.1-2024, T/ITS 0224.1-2025), China Unicom RS-MEC infrastructure, and European and US C-V2X programs confirms that both institutional sides are converging on the roadside traffic node without a coordination standard. A fifteen-run Multi-Agent Proximal Policy Optimization (MAPPO) simulation validates the architectural family: Mode 0a in shared-pool baseline sits at the analytical symmetric-Nash coordination floor; Mode 0c with demand separation achieves strict Pareto improvement for both traffic classes (M0 PDR 0.999, M1 PDR 0.998 at $ρ_{\rm pool} \leq 1$) and lifts the worst-TTI delivery ratio from near-zero to 0.601 -- the only configuration satisfying the latency safety requirement structurally. We call for a 3GPP study item on Mode 0 within the NR-V2X sidelink enhancement work programme.

翻译：3GPP V2X资源分配框架定义了两种实体类型——基站和车辆UE——以及LTE和NR两代技术中的四种模式。我们证明该二元分类在结构上是不完备的。基站在高密度交通节点处主导的调度会发生饱和，产生尾延迟故障，即使平均数据包投递率接近服务等级目标时此故障依然存在。UE自主性在本质上无法对遮挡交通参与者提供先兆预警，也不足以应对大范围级联环境危害。我们提出模式0——一种新型3GPP V2X类别，其定义实体为路侧计算单元（RCU）——一种由交通管理部门拥有的基础设施集合，集成高空感知（Seeing）、侧行通信（Speaking）与本地计算评估（Thinking）。模式0定义了从模式0a（全被动UE，保证最小值）到模式0c（全主动UE，最优目标）的子族谱系。来自中国国家标准（DB11/T 2329.1-2024、T/ITS 0224.1-2025）、中国联通RS-MEC基础设施以及欧美C-V2X项目的融合部署证据证实，双方在缺乏协调标准的情况下正趋同于路侧交通节点。基于十五次运行的多智能体近端策略优化（MAPPO）仿真验证了该架构族：共享池基线下的模式0a位于分析对称纳什协调下限；具有需求分离的模式0c对两类交通实现严格帕累托改进（在$ρ_{\rm pool} \leq 1$时M0 PDR 0.999，M1 PDR 0.998），并将最差TTI投递率从接近零提升至0.601——唯一在结构上满足时延安全要求的配置。我们呼吁在NR-V2X侧行链路增强工作计划中设立关于模式0的3GPP研究项目。