近年來，車載網路(VANETs)成為一個值得討論的議題， VANETs是行動隨意網路(MANETs)的一種應用，但是環境與行動隨意網路有所不同，如節點移動速度、網路拓撲變化快速等。所以MANETs所提出的方法大多不適用於VANETs中。
車載網路提供了許多種應用，如增加行車安全、降低道路擁塞和增加行車周邊服務等，這些都為車載網路衍伸出很多議題。當有事故發生時，有效的將警告封包(Alert message)擴散至事故周圍的道路來增加行車安全避免二次事故成為最重要的議題之一，傳統的Flooding方法提供了很好的封包觸及率(Reachability)但也因為設計簡單而容易造成廣播風暴(Broadcast Strom Problem)，造成有限網路資源的浪費。本研究提出一個新的方法，透過我們的方法可以在任何不同的道路上有效的轉傳並與Flooding有差不多的封包觸及率並且能有效的減少警告封包的傳送造成不必要的資源浪費。透過NS2網路模擬器的實驗證明，我們提出的演算法可以提升確實效能。

Vehicular Ad-hoc Networks(VANETs) become a very popular issue in recent years. VANETs are one kind of Mobile Ad-hoc Networks(MANETs), but it possesses different properties, such as faster nodes mobility and quick topological change. Therefore, the method employed on MANETs would be not suitable for VANETs.
VANETs have many kinds of applications such as increasing driving safety, decreasing traffic congestion and offering better driving services. One of the most important issues is how to disseminate “Alert message” efficiently such that, when accident happens, it can be warning drivers to increase driving safety. The traditional method, Flooding, provides a good reachability but it may causes “Broadcast Strom Problem”, resulting in bandwidth abusing.
In this thesis, we propose the bidirectional broadcasting scheme(BBS) whcich ensures bidirectional broadcasting on any roads, such that it can be suitable for any scenarios. The simulations are conducted with network simulator NS2. The simulation results show that the proposed scheme can achieve high reachability and low bandwidth usage.

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