近年來臺灣高速公路硬體設施完善,目的在於「減少使用者之旅運成本」,並期望與「提升高速公路服務效率」之間取得平衡,使高速公路達到較佳之運輸表現。而提昇高速公路運輸效率前,必須瞭解高速公路之車流表現,其中車流速度無疑是最重要關鍵因素之一。然而其與流率間之相互關係及推估,卻深受其他特性影響,包括道路配置、線型、環境地形…等。國內過去交通部運輸研究所使用美國聯邦公路總局BPR (Bureau of Public Roads)時間成本函數構建車流速度推估模式,但該模式並未就前述因素提出具環境特性較細緻之模式對應係數組合,致使其在應用面上並未發揮作用。 因此本研究擬重新檢視BPR時間成本函數,首先探討各係數在BPR時間成本函數中產生之數理特性,及其作為不同環境特性影響替代(proxy for unexplained factors)之可能;再藉由實務資料,分析車流及環境特性對函數推估係數之影響,作為發展環境特性對應模式之依據;並利用偵測數據調校對應模式之推估準確性。 因立基於現用規範,本研究在管理策略上與設計面之衝突可大幅減少,更期能反饋在設計面向上之環境差異考量。此外,對於缺乏實務資料之路段,此對應模式之建立在資料之差補上亦有其應用之價值。
In recent years, the facilities of Taiwan area National freeways have been constantly improving. It is desirable to strike a balance between "reduction of transportation costs" and "improvement of freeway efficiency". And then achieve better performance of freeway. Before that, it is necessary to know the performance of freeway, in which speed is undoubtedly one of the most important key factors. However, the variety of relationship between speed and flow depend on many characteristics, such as number of lanes, road type, road condition, and terrain. But these factors were not fully considered in BPR function which calibrated by Ministry of Transportation and Communications in 2004, so that it doesn’t fit well in following application. Therefore, this study intends to re-examine the BPR function. First, we discuss the mathematical properties of the coefficients in the BPR function and their possible proxy for unexplained factors. And then analyze the impact of traffic flow and environmental characteristics on the estimated coefficients of the function by practical data. And use the detection data to adjust the accuracy of the model. Further more, the conflict between management strategy and design can be greatly reduced, and expect to feedback on the road with different environmental characteristics. In addition, the model is valuable in the imputation for the road lack of practical data.