在無線車用網路中，十字路口是一個特殊的場景。道路兩旁的建築物會對無線訊號造成干擾，而且會將配備有無線傳輸功能的車輛分割成不同的群組，使的不同道路之間的車輛必須經由一個有較好傳輸品質的中繼傳輸者才能完成不同路口車輛之間的資訊交換。
協同碰撞預警機制必須藉由週期性廣播車輛的安全訊息(Safety Message)才能讓車輛之間了解彼此的行車狀態，而且安全訊息廣播的週期必須限制在一定的區間內。為了在十字路口的場景中實現協同碰撞預警機制，本篇論文提出兩種通訊協定，分別為結合時間分割(Time Division)和空間分割(Spatial Division)的集中式通訊協定，和一個藉由路口上的車子執行廣播機制的分散式通訊協定。並且使用網路模擬器Network Simulator 2 驗證其效能。由模擬的結果顯示集中式的通訊協定可以提供足夠的封包接收率，而且顯示路口上通訊協調器(Communication Coordinator)的必要性。最後，藉由分析集中式的通訊協定而獲得系統的最大容量。

A distributed protocol and a centralized protocol that support the cooperative collision warning (CCW) system for crossroads are proposed. The CCW system must periodically broadcast safety messages with limited latency. The feature of crossroads that separates vehicles into different clusters by buildings along the streets is utilized, and combines time division and space division in the proposed protocols. The necessity of a communication coordinator for crossroads is investigated.
The movements of vehicles are generated using the SUMO software package. The performance of the proposed protocols is quantified using Network Simulator 2 (NS-2). Simulation results show that both the packet receive rate of the proposed centralized protocol is sufficient and the weakness of no relay guaranteed in distributed protocol. The effect of a communication coordinator is determined. An extension of the 3-level renewal process is derived to present the hidden terminal problem in the distributed protocol. Finally, the maximum capacity of the proposed centralized protocol is demonstrated by an analytical model.

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