高速公路出口匝道區段容量與服務水準評估方法之研究

Abstract

摘 要 目前國內用來評估匝 道容量與服務水準所採用的「台灣地區公路容量手冊」之方 法，主要 是參考美國1985年版「公路容量手冊」(Highway Capacity Manual, HCM) 修正而得，由於台灣與美國交通特性上之差異，在實用上有其限制，且美 國於1994年已重新修訂其「公路容量手冊」，為提昇本土化分析方法之實 用性，本研究參考 美國1994年「公路容量手冊」修正版之方法，依我國 交通特性，發展一套適合我國車流特性之出口匝道區段容量與服務水準評 估方法。主要研究內容與方法如后： 1.調查、分析出口匝道區段之 流率、速率、密度等車流資料與運行特性，並據以建 立車流模式。 2.探討出口匝道區段服務水準最差地點，作為主要評估對象。 3.分析 出口匝道區段車流分出行為所影響之主線車道數。 4.構建受影響車 道之流量預測模式。 5.構建受影響車道之車流模式，進行容量推估。 6.建立受影響車道之服務水準評估指標模式。 7.研擬適合我國地區特 性之出口匝道區段服務水準評估程序與方法。 本研究所獲致之主要結 論如后： 1.出口匝道區段服務水準最差地點並不固定，主要是隨著流 率而變動。 2.出口匝道區段受影響之主線車道數，主要為最外側車道 ，而且間接影響到外側 第二車道，與美國1994年「公路容量手冊」 之結論雷同。 3.本研究以流量~密度~速率(K~Q~U)關係曲線配試法進 行外側二車道車流模式構建 ，據而進行容量評估。發現出口匝道區 段外側二車道容量因主線車道數不同而有 所差異；主線為二車道 與三車道，其容量為4,400PCPH(每車道為2,200PCPH)； 四車道則 為4,600PCPH(每車道為2,300PCPH)。 4.本研究選定以密度作為主要評 估指標，速率、流量作為次要評估指標，利用實際 調查資料構建密 度及速率預測模式，做為評估服務水準之依據。 5.本研究所觀測之臨 界密度約發生在40pcu/km/ln，與「台灣地區公路容量手冊」 基本 路段之臨界密度(52pcu/km/ln)有所差異。因此出口匝道區段服務水準等 級 之界定準則與基本路段略有不同。 Abstract The existing method in "The Highway Capacity Manual(HCM) in Taiwan" forthe evaluation of capacity and level of service(LOS) on freeway off-rampjunction is modified from the "Highway Capacity Manual in U.S.A., 1985". Thepractical applicability is limited, due to the difference of trafficcharacteristic between Taiwan and U.S.A.. To improve and enhance theapplicability of the method, this research, making reference to the 1994revised edition of HCM in U.S.A., develops an evaluation approach ofcapacity and LOS on off-ramp junction area, which is more suitable for thetraffic characteristic in Taiwan. The contents and approaches of thisresearch are as following: 1. To collect and analyze traffic flow data and characts., such as volume ,speed,density ect., and develop traffic flow models. 2. To identify the bottleneck on off-ramp junction area, which is considered as the main evaluation location. 3. To analyze the number of main lanes influenced by the behavior of diverging flow on off-ramp junction area. 4. To develop the volume prediction model for the influenced area 5. To develop the traffic flow models for the influenced lanes, which are used to evaluate the capacity. 6. To develop LOS measure of performance models, for the influenced area. 7. To establish the LOS evaluation procedure and method， that fit Taiwan's traffic flow characteristic on off-ramp junction area. The main conclusions drawn from this study are: 1. The bottleneck on off-ramp junction area is not fixed. The location changes mainly with the diverging traffic volume . 2. Lane 1 and Lane 2 of mainline are the influenced area of freeway off-ramp junction area. This conclusion is same as "HCM in U.S. A.,1994". 3. This study develops a set of traffic flow models for the influenced area, using volume~density~speed (K~Q~U) curve fitting approach, which are used for capacity evaluation.. For 2 or 3-lane freeway segments, the capacity is 4,400 pcph (2,200 pcph for each lane). For 4-lane freeway segments, the capacity is 4,600 pcph(2,300 pcph for each lane). 4. This study chooses density as the major MOE of LOS. Speed and V/C volume as secondary MOE. Density and speed prediction model are developed by use of on-site data, to be used in LOS evaluation. 5. The critical density is found to be around 40 pcu/km/ln, which is a different from the freeway basic segment. Therefore, LOS criteria is different between off-ramp area and basic segment.