Road Networks in an Expanding Circular City

The effect of growth in the number of persons living in the suburbs of an idealized circular city and working in a central business district of constant size is investigated in the case of five alternative basic road systems. It is shown that the total city size, relative to the size of its central business district, can increase only up to a critical value beyond which a major change in the basic road network is necessary to ensure efficient travel. Critical values for the ratio of the density of work places to homes are then obtained. The criteria used to evaluate the road networks are distance traveled, road space required, and travel time.