Abstract
The Taiwan Area Highway Capacity Manual of 2001 describes free-flow speed as an input for level-of-service analysis of urban arterials. However, it does not provide a tool for estimating free-flow speeds on urban arterials. To bridge this gap, this study collects free-flow speeds from fourteen urban arterials in three cities of Taiwan. The data were first used to investigate the characteristics of free-flow speed in relation to vehicle type, geometric design, and speed limit. They were then used to develop models for estimating average free-flow speed and to establish the probability distributions of the free-flow speed of individual vehicles. Intersection spacing, speed limit, median type, lane location, and vehicle type are found to have obvious effects on average free-flow speed. The results of this study will be useful in revising the existing methodology for analyzing Taiwan’s urban arterials. They are also useful for calibrating microscopic models for simulating urban traffic flows.
