西濱快速公路自由車流速率特性及其應用之研究

Characteristics of Free-Flow Speed on the Sibin Expressway and Their Applications

自由車流速率為分析公路運作特性之一關鍵參數，此參數早已廣泛應用於美國公路容量手冊以分析非阻斷性車流之容量與服務水準。自由車流速率亦為各類公路估計延滯、平均速率、油耗、空氣污染之一不可或缺的資料。國內以往少有對於自由車流速率特性之研究，以至於目前沒有合適的方法來分析各類型公路的容量與服務水準，特別是有號誌化路口的市郊或郊區公路。本研究係針對西濱快速公路，以進一步探討自由車流速率之特質及用以分析號誌化公路設施的應用意涵。本研究除了討論自由速率如何受到某些因素之影響，更指出如何將一號誌化公路區分為不同路段之分析課題，並檢視建立代表性之流率與速率關係以進行容量分析時，必須應用自由車流速率之重要性。 Free-flow speed is a critical parameter in analyzing the operating characteristics of highways. This parameter is used extensively in the U.S. Highway Capacity Manual for analyzing the capacities and levels of service of highways with uninterrupted traffic flows. Free-flow speed is also an indispensable input to the estimation of delays, average speeds, fuel consumptions, and vehicle emissions on a variety of highways. Very little research, however, has been conducted in Taiwan to understand the characteristics of free-flow speed. This has led to a lack of proper methods for capacity and level-of-service analysis of many types of highways, especially signalized suburban and rural highways. Focusing on the Sibin expressway, this study provided a better understanding of the nature of free-flow speed and its implications on the capacity analysis of signalized highway facilities. Aside from revealing how free-flow speed may change with several factors, the study addressed the issue of how a signalized highway should be divided into sub-sections for analysis. It also examined whether or not free-flow speed should be used to establish representative flow-speed relationships for capacity analysis.

Free-flow speed is a critical parameter in analyzing the operating characteristics of highways. This parameter is used extensively in the U.S. Highway Capacity Manual for analyzing the capacities and levels of service of highways with uninterrupted traffic flows. Free-flow speed is also an indispensable input to the estimation of delays, average speeds, fuel consumptions, and vehicle emissions on a variety of highways. Very little research, however, has been conducted in Taiwan to understand the characteristics of free-flow speed. This has led to a lack of proper methods for capacity and level-of-service analysis of many types of highways, especially signalized suburban and rural highways. Focusing on the Sibin expressway, this study provided a better understanding of the nature of free-flow speed and its implications on the capacity analysis of signalized highway facilities. Aside from revealing how free-flow speed may change with several factors, the study addressed the issue of how a signalized highway should be divided into sub-sections for analysis. It also examined whether or not free-flow speed should be used to establish representative flow-speed relationships for capacity analysis.