近年來歐美各國大力推動現代圓環(Modern Roundabout),並且強調該路口形式相較於傳統圓環(Traffic Circle)或是無號誌十字路口(4-ways stop)都是更為有效率、更為安全。台灣不論任何地區,機車數量在車流組成當中都佔了相當大的比例。台灣混合車流是否能夠適用現代圓環或是傳統圓環這樣的路口形式,是本研究所想要釐清的問題。而影響路口績效最重要的指標便是路口容量,因此混合車流在無號誌圓環的容量分析是本研究的重點。 本研究回顧過往現代圓環容量的研究,並實際調查觀察台灣無號誌圓環的駕駛行為,依照接受間距理論提出一套能夠適用於混合車流的現代圓環與傳統圓環容量估算式。其中考量的客觀變數包含:車道數、混合比、圓環半徑與轉向比;而駕駛人行為參數包含:汽車飽和車頭距、機車飽和車頭距與各車種組合下的臨界接受半間距。本研究亦完成了台灣混合車流的駕駛人行為參數校估。本研究所提出之容量計算式,經過國際知名車流模擬軟體VISSIM的驗證,並且平均絕對誤差率MAPE值在10%以內,顯示本容量計算式確實能夠估算出混合車流下圓環的容量值。 本研究所提出的容量計算式不僅能夠得到分析情境下的容量值,更可以經由換算得到該情境下的機車PCE值。由PCE值可以更精確的計算該路口的飽和度,進而透過公式計算得到該情境下的平均每車延滯,可供分析路口服務水準。 另外,為了了解無號誌圓環是否適用於台灣混合車流情境下,本研究利用校估所得的駕駛人行為參數,模擬了無號誌圓環、號誌化圓環、無號誌十字路口與號誌化十字路口等路口形式。根據模擬結果比較不同路口型態在不同交通條件下的容量。本研究的成果當中顯示,現代圓環確實在某些情況下比其他各種類型的路口效率更高。大多數情況下,號誌化現代圓環能夠比其他路口形式有更高的效率。並且根據模擬結果,就容量的觀點提出各種情境之下最適合的路口形式,簡化成一決策流程圖,供未來規劃者與研究人員參考。
Recently, many countries in Europe and the United States promote modern roundabout and emphasize that this intersection type is safer and more efficient than traditional traffic circle or 4-ways stop. In Taiwan, scooters cover a large proportion of the traffic flows. The feasibility of traffic circle or modern roundabout in mixed traffic flow in Taiwan is the topic in this research. Therefore, this research focuses on the capacity of unsignalized roundabout and traffic circle for the mixed traffic flow. Based on previous studies of the gap acceptance theorem of modern roundabout and a survey of the driving behaviors at unsignalized traffic circles in Taiwan, this research developed a set of estimation formulas which can be used in both modern roundabout and traditional traffic circle for mixed traffic flow. Many objective variables were considered, including the number of lanes, the scooter rate, the radius and the turning rate. Driver behavior parameters contained the saturated headway, the follow up time and the critical lag. This research accomplished driver behavior parameters in order to estimate the mixed traffic flow in Taiwan. The capacity formulas were verified through the traffic simulation software, VISSIM. And the MAPE values were under 10%. It showed that the capacity formulas could be used for the mixed traffic flow with accuracy. This research also provided a method to obtain the scooter’s PCE value on roundabout. Through the PCE value, the average delay of each vehicle unit could be calculated, and the level of service can be analyzed. Additionally, this research simulated the capacities of different types of intersections, such as that of unsignalized roundabout, signalized roundabout, 4-ways stop and signalized crossroads. The result showed that the efficiency of modern roundabout could be better than other types of intersection under some situations. In most situations, signalized modern roundabout can have a higher efficiency than other types of intersections. According to simulated results, a decision flowchart could be generated and provided to planners and researchers in the future.