國道五號雪山隧道長度12.9公里，採雙孔單向之行車設計，名列世界第五長公路隧道。雪山隧道南北雙向全線佈設交通資料蒐集設備，除了達到監控隧道內車流與突發狀況外，亦可協助探索交通界目前相當缺乏的長隧道行車特性。 本研究透過影像資料觀測個別車輛以蒐集交通資料，將有助於了解駕駛人行車速率變化特性。由於資料不易取得，因此，路段以非連續觀測之方式來呈現個別車輛行駛於長隧道行車速率變化行為。研究目的主要是為了探討自由行駛車輛之微觀與巨觀特性，並探討駕駛人以期望速度行駛於長隧道內，沿線觀測路段之平均速率變化，找出於隧道內影響駕駛人速率改變最大之路段與個別隧道(南、北向)全線平均速率比較；然後，延伸探討南北向兩隧道孔內，在環境與設備相同之條件下，比較南北向路段自由行駛車輛之全線平均速率，是否受到隧道內幾何線形(坡度)之影響。 研究結果發現(1) 在自由車流之狀態下，無論隧道南向或北向路段，車輛行駛於隧道中段時，其路段平均速率皆會下降；(2)行駛於內車道平均速率顯著大於外車道平均速率；(3)大客車與小型車之平均速率並無顯著差異；(4)隧道內之坡度並不影響自由車流平均速率。 The 12.9 km long Hsuehshan Tunnel sits on Taiwan’s National Highway No. 5. It is a two-bore (two lines working) tunnel and is the fifth longest highway tunnel in the world. Throughout the tunnel, monitoring devices are deployed to collect traffic data, control traffic flows, detect unexpected events, and identify the characteristics of traffic flows, which is under-explored in long tunnels. This study collects the video recordings on individual vehicles in order to find out the characteristics of traffic flow. Such information will provide deepen insight into the speed change of each vehicle. Because of the inconvenient access to the facilities of the video recordings, the speed change of the individual vehicle in the tunnel is analyzed by non-continuous observations. The aim of this study is to explore the characteristics of free-flowing vehicles from both micro- and macro-perspectives, while trying to identify the average of speed change when drivers are driving in long tunnels. By doing so, the sections where the largest speed change occurs are pinpointed and compared to the average speed of both the north-bound and the south-bound lines. Next, the average speed of free-flowing vehicles in both the north-bound and south-bound lines, are equipped with identical devices, and we will discuss the effect of grade on the speed. The results show that (1) whether it’s in the north-bound or south-bound line, the average speed of free-flowing vehicles tends to decrease in the mid sections (2) the average speed of the inner lane is considerably higher than that of the outer lane (3) there is no significant difference between the average speeds of large and small vehicles and (4) the average speed of free-flowing vehicles is not affected by the grade inside the tunnel.
