Cities as Organisms: Allometric Scaling of Urban Road Networks

Abstract

Just as the cardiovascular network distributes energy and materials to cells in an organism, urban road networks distribute energy, materials and people to locations in cities. Understanding the topology of urban networks that connect people and places leads to insights into how cities are organized. is paper proposes a statistical approach to determine features of urban road networks that affect accessibility. Statistics of road networks and traffic patterns across 425 U.S. cities show that urban road networks are much less centralized than biological vascular networks. As a result, per capita road capacity is independent of the spatial extent of cities. In contrast, driving distances depend on city area, although not as much as is predicted by a completely centralized model. is intermediate pattern between centralized and decentralized extremes may reflect a mixture of different travel behaviors. e approach presented here offers a novel macroscopic perspective on the differences between small and large cities and on how road infrastructure and traffic might change as cities grow.

Allometric scaling of foraging rate with trail dimensions in leaf-cutting ants

“…The trails in Atta colonies seem analogous to the transport and supply networks of cities [11,29,30]. Resources conveyed along these transport paths determine the economic activity and ultimate productivity (population growth or economic output) of the societies they serve.…”

“…Resources conveyed along these transport paths determine the economic activity and ultimate productivity (population growth or economic output) of the societies they serve. Although the geometry of transportation networks is more decentralized in cities than in Atta colonies or organismal vascular systems [30], traffic volume is highly concentrated on a small portion of the total road length in cities [31], much as the traffic of Atta foragers is concentrated on permanent, central trunk trails, while smaller, peripheral trails to particular foraging sites change over time [16,18]. Road length scales below isometry (i.e.…”

Energy and time determine scaling in biological and computer designs

“…traffic flow within cities [49] and among ant nests [50]. Tainter et al [51] argue that complex human and ant societies are able to exploit 'low-gain' energy systems-those that provide low concentrations of dispersed energy, but that are ubiquitous and therefore can be exploited by complex systems capable of processing and storing vast quantities of energy.…”

Superlinear and sublinear urban scaling in geographical networks modeling cities

“…Such similarities are found not only in the correspondence between constituent elements of cities and living organisms, but also in allometric scaling [1]. Similar to living organisms with the basal metabolic rate of an animal proportional to the 3/4 power of its body mass M [2,3] or the breathing rate (or heart rate) proportional to M −1/4 [4], there are various quantities related to activities or performances of cities such as urban road systems [5], night illuminations [6], and size distribution of buildings [7] that are described by power-law relations [8]. Power-law scaling has also been found in the morphology and evolution of cities and argued from a viewpoint of fractal cities [9][10][11][12][13].…”