交通壅塞一直以來是政府亟欲改善而駕駛者一直無法避免的問題，交通壅塞會導致大量社會成本支出，而車載網路（Vehicular Ad-Hoc Network, VANET）可以透過廣播、接收路況資訊解決壅塞的問題。傳統機制沒有考量在同一路段有雙向車道的設計，本研究提出一個稱為DRP(Directional Route Planning)的機制。依據行駛過程中路段的起始座標與終點座標關係去定義交通報告的方向性。車輛在行駛過程中會廣播此路段的行駛時間，並且也會廣播透過接收來的路況資訊。當車輛獲得了足夠的即時路況資訊後，就可以規劃出一條最短行駛時間路徑。本研究提出的機制在資料散佈同時加入了方向性的資訊，讓資訊更為準確進而提升路徑規劃的效能，並且為了應付壅塞的都市交通環境，提出了權重遞減策略。
本研究使用NS2進行車載網路模擬，並且與Traffic Rep與Traffic Info機制作比較，實驗的結果顯示，本研究的散佈機制比Traffic Rep與Traffic Info機制更能夠有效地散佈路況資訊，並且縮短行駛時間。

Traffic congestion is a problem needed to be solved by the government to provide an efficient transportation system for the drivers. A Vehicular Ad-Hoc Network (VANET) can be used to broadcast and receive traffic information to solve the congestion problem. The existing methods for navigation using VANETs did not consider the fact that there is two-way traffic on a street in a city. In this paper, we propose a method, termed DRP (Directional Route Planning) for navigation in a city. We define the direction of a road segment according to the relationship between the starting coordinate and the end coordinate of the road segment. A vehicle disseminates not only its traveling time required for a road segment but also the traffic reports received from other vehicle. When a vehicle receives enough real-time traffic information, it can plan a traveling route with the shortest travel time. We also propose a strategy called the decreasing weight to deal with the large volume of traffic reports generated by the VANET in a congested road.
We performed several experiments using NS2. We compare the performance of the DRP with those of the Traffic Rep and Traffic Info methods. The experimental results showed that DRP is more effective than the existing methods in disseminating traffic information and in reducing the travelling time.

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