Modelling the Relationship of Infrastructure and Externalities Using Urban Scaling

A surprising aspect of the agglomeration economy is the lack of attention to the impact on the physical environment. Even in the field of spatial planning, road infrastructure has been built in situations where the consideration of the agglomeration economy is insufficient. The urban scaling proposed by theoretical physicists is an excellent tool to solve this problem but is only at the level of conceptually comparing the index values extracted by individually scaling socioeconomic indicators and urban infrastructure with the population. Accordingly, the frame model scales the urban infrastructure with the number of workers by industry sector and includes a density externality structure so that the agglomeration economy and urban infrastructure can be linked directly. Three experiments were conducted to verify the frame model: first, the Zipf distribution of economic activity found straight lines in large cities, peaks in medium cities and hills in small cities; the cities were categorised by urban size. The second experiment verified that linearisation was due to Jacobs externalities, while the third confirmed that the peak was due to Marshall–Arrow–Romer externalities. Moreover, in distinguishing traditional and modern industries, thresholds of 0.6 in agglomeration and 1.0 in economic interaction were found.