A Grid Is Not a Tree: Toward a Reconciliation of Alexander's and Martin's Views of City Form

Abstract

Christopher Alexander famously declared that "a city is not a tree," while Leslie Martin declared that "the grid is [a] generator." This article investigates how Alexander’s call for overlap, adaptability, and order can indeed be manifested in grid networks, as Martin claimed. Order has been measured using the entropy of street orientation, while adaptability has been denoted by the streets' betweenness values. Through the analysis of Abu Dhabi's neighborhoods and global urban areas, the study reveals that overlap, order, and adaptability can coexist in gridded street network. A fine-grain scale of the grid plays a critical role in supporting the quality of urban space. To foster adaptation, planning policies should focus on adaptability providing room for informal and spontaneous growth. We conclude by noting that this approach represents a reconciliation between Christopher Alexander's views and those of Leslie Martin.