Because bottleneck phenomenon in road sections of uninterrupted flow in expressways is a very interrupting factor in smooth traffic function, both finding its cause and establishment of its countermeasures are urgently needed. The phenomenon regularly takes place at specific vertical alignment sags and entrances of tunnels, and analysis on its occurrence and related macro-factors has been conducted mainly using data from vehicle detectors. However, approaches to micro-analysis which more distinctly explains those composing factors have not been conducted much because an appropriate method for it has not yet been developed. In fact, readings from VCR pictures which have been the only way for observing occurrence and conveyance of reduction shock wave, change in traffic flow, or others are in defect of efficiency in procedures and produce high possibility of errors. As a trial of more precise micro-analysis on bottleneck phenomenon, by application of aerial survey technique, the authors spatially observed expressways and measured instantaneous relative position and velocity of vehicle platoons. This paper presents a principle of the measuring method and results of the micro-analysis, as well as prospective of explanation of bottleneck phenomenon.
Abstract