抄録
The article describes the nature of highway traffic flow mainly composed of automotive four wheelers, and also introduces several technical issues to be solved by engineers. The one of the way of understanding the highway traffic flow is treated as continuous fluid flow, otherwise as dispersive individual vehicle movements. The short history of these two streams of traffic flow theories are reviewed, and the most basic diagrams useful in the analyses of highway traffic flow, such as time-space diagram, fundamental diagram and cumulative volume curve, are also introduced. One aspect of the classification of highways is the distinction of uninterrupted and interrupted flow facilities. The discharge flow from the stop line at one approach to a signalized intersection from the start of a displayed green traffic signal is the maximum flow for an interrupted flow highway facilities. The nature of 'traffic congestion', which is a typical phenomena occurred at a highway capacity bottleneck section, is discussed in general. The traffic flow is dealt as a two-phase flow with congested and uncongested flow regimes. The concept of 'traffic congestion' in an interrupted flow facilities are different from those in uninterrupted flow ones. As a simplification, Shock wave theory which can describe the direction and the wave speed of extension or diminution of the boundary of discontinuous different two highway traffic region, such as congested and uncongested traffic flow region, is introduced. The amount of excess traffic demand over a bottleneck capacity for recursive traffic congestion phenomena is also discussed.
