國道五號雪山隧道長度12.9公里，名列世界第五長公路隧道。雪山隧道南北雙向全線佈設車流資料蒐集設備，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。 本研究觀測個別車輛以蒐集交通資料，將可有助於一般化駕駛人行車速率變化特性。由於資料取得不便，因此以路段而非連續觀測之方式來表達個別車輛行駛於長隧道行車速率變化行為。研究主軸係探討自由車流車輛與行車干擾車輛巨觀與微觀特性，並且探索駕駛人以期望速度行駛於長隧道內，於全線觀測路段之平均速率變化，提出因隧道單調環境而影響駕駛人速率改變最大之路段，以建議管理者做為決策增加長隧道道路環境視覺變化之參考。研究結果發現 （1）無論是自由車流或是行車受干擾車輛，於隧道全線速率變化皆呈一類V型緩和變化型態（2）以期望速度行駛之駕駛人受隧道單調環境衝擊影響最大為長隧道8公里處，建議長隧道長度在8公里上下，也就是行車速率變化最大之隧道中心路段，應加強隧道壁面視覺變化，幫助駕駛人不再持續受到隧道單調環境影響。 With a length of 12.9 km, the Hsuehshan Tunnel is the longest tunnel on Taiwan’s National Highway 5 and the fifth longest highway tunnel in the world. Inside the two one-way tubes, there are a number of equipments that collect traffic data. These equipments can not only monitor control traffic flow and unexpected events but also explore traffic characteristics in a long tunnel The study mainly focuses on observing single-vehicle to collect traffic data and analyzing the variation characteristics of average speed. Because image data acquired inconveniently, we express the single-vehicle variation characteristics of average speed by observing the arc. The research analyzed the macroscopic and microscopic characteristics of free flow and disruptive flow. Not only we explore variation of average speed under desired speed, but also offer the influence of the arcs on average speed in the monotonous environment. The project is expected to provide the managers suggestion that is added variation of the tunnel wall. The analysis shows that the variation characteristics of average speed in the long tunnel have an gentle variation of V-type regardless of free flow and disruptive flow. The influence of free flow on monotonous environment is self-evident. The length of 8km , center of Hsuehshan Tunnel , is the maximum variation of average speed. We suggest that the managers should strengthen the variation of tunnel wall to help the drivers avoid falling into monotonous environment.