機車專用道實際使用疏解寬度及容量估計之研究

ESTIMATION OF ACTUAL DISCHARGE WIDTH AND CAPACITY OF EXCLUSIVE MOTORBIKE LANES

探討機車專用道容量問題，必須先了解機車之疏解特性，但由於國內先前有關的研究，未考量專用道分隔方式 (如標線或實體分隔) 之差異，且未說明機車專用道寬度如何量測，亦未適當交代取樣之週期數，以致於沒有具體的共通成果，實務上難以運用。因此，本研究錄影蒐集臺北市八個機車專用道的現場資料，其原始車道寬介於1.7 ~ 3.4公尺間，每個調查地點至少有50個週期，以停止線為基準線，記錄停等機車後輪通過基準線之橫向位置軌跡，並提出以α截集的觀念來決定「實際使用疏解寬度」；同時，計算分析每2 秒之機車疏解率。分析結果顯示：(1) 將 α 訂為0.05時，所得之實際使用疏解寬度可有效地作為估計飽和流率之參數，故八處調查地點的實際使用疏解寬度在1.3 ~ 3.4公尺之間；(2) 各車道疏解率在綠燈啟亮後10秒開始平穩，顯示所調查之機車專用道存在飽和流率；(3) 飽和流率隨著實際使用疏解寬度的增加而明顯地增加；(4) 經利用實際使用疏解寬度 (W，公尺) 及其飽和流率 (S，機車／小時)，可建立推估式S = 6168.6 + 441.9W2，其判定係數 (R2) 為0.88且參數均顯著，本研究進一步應用於估計不同綠燈時段下之容量。這些研究成果可以提供未來設置機車專用道之參考。

The characteristics of motorbike discharge behaviors are very importantfor the analysis of the capacity of exclusive motorbike lanes. However, previousresearches disregarded the influences of different separation types (i.e. roadmarking or physical separation) and did not illustrate the methods of measuringlane-width, and the numbers of sampling cycles as well. The findings in previousstudies were inconsistent and impractical. This study collected field data usingcameras at eight sites with lane-widths ranging from 1.7 to 3.4 meters in Taipeicity, with more than 50 cycles at each site. Researchers recorded the horizontalpositions of back-wheels of motorbikes passing the reference line, which wasidentified as a stop line, and determined the actual discharge-width by anα-percentage cutting rule. In the meantime, the numbers of discharged motorbikeswere counted every 2 seconds. The findings of this study were summarizedas follows. (1) The value of α was 0.05 because the corresponding actual discharge-width could be effective in estimating saturation flow rates. The actualdischarge widths at these eight sites ranged from 1.3 to 3.4 meters. (2) The dischargerates became stable 10 seconds after green light turned on. It showedthat the saturation flow rate exists. (3) It was found that the saturation flowrates clearly increased when the available lane widths widened. (4) Based on theavailable lane-width (W, meters) and the corresponding saturation flow rate (S,motorbikes/hr), a simple regression model was estimated as S = 6168.6 +441.9W2. The coefficient of determination (R2) was 0.90 with all estimated parametersbeing statistically significant. Furthermore, this study estimated thecapacities under various green intervals based on the estimated saturation flowrates. The results of this study are essential for setting up exclusive motorbikelanes in the future.