A Schematic Urban Street Network-Display Algorithm

The link-node network is the most commonly used model for representing a large-scale urban street system. It is easy to formulate a mathematical model which describes the complicated spatial and temporal urban-street-related problems on such a simplified network representation. However, recently developed microscopic network traffic models contain important details which cannot be depicted on the link-node diagram. This paper describes a computer-graphics algorithm which can generate a lane-detailed schematic urban street network display. The algorithm is very comprehensive, and it can accommodate various types of urban street configurations. The regular four-approach, right-angle intersection can be displayed most accurately. However, intersections with more or less than four approaches and/or links intersecting at an angle other than 90-deg can be generated satisfactorily. One-way streets intersecting two-way or one-way streets can also be depicted. Furthermore, roadways where the number of lanes changes (for example, from two lanes to three lanes, or from two lanes to one lane) can also be plotted. The overall quality of the display generated by this algorithm is satisfactory. The required input data is relatively simple, although the time associated with the input data preparation is short. In addition, applications using this algorithm are also discussed.