The concept of urban ‘walkability’ has come to occupy a key role at the nexus of a series of multidisciplinary fields connecting urban design and planning to broader issues of public health, climate change, economic productivity and social equity. Yet the concept of walkability itself remains elusive – difficult to define or operationalise. Density, functional mix and access networks are well-recognised as key factors: density concentrates more people and places within walkable distances; functional mix produces a greater range of walkable destinations; and access networks mediate flows of traffic between them. This complex synergy of density, mix and access – herein called the urban DMA – largely stems from the work of Jacobs. With an approach based in assemblage thinking we show that each of these factors is multiple and problematic to define or measure. Any reduction to a singular index of morphological properties can involve a misrecognition of how cities work. We argue that walkability is a complex and somewhat nebulous set of capacities embodied in any urban morphology, and that it should not be conflated with nor derived from actual levels of walking.

URBAN DESIGN International is a scholarly publication with a strong practitioner emphasis. It is relevant for all of those involved in architectural and planning education and practice. It is relevant for urban designers, architects, planners, surveyors and landscape architects and all professionals concerned with urban development and design.

Functional or land-use mix has been seminal to urban design and planning for over 50 years. Mixed-use reduces the need for travel, increases walkability and generates street-life intensity. In this paper we review existing methods of measuring functional mix and rethink the ways in which it might be conceived, measured and mapped within a framework of assemblage thinking. We suggest a live/work/visit triangle as a promising method with a focus on the interconnections between functions rather than functions in themselves. Mapping techniques are developed to reveal the ways functional mix changes at different scales from streetscape to walkable neighbourhood. This approach is tested on detailed floor area databases from the cities of New York, Barcelona and Bogotá. Rather than reducing mix to an index, such mapping reveals each city as a mix of different mixes. These maps can be understood as urban X-rays that enable interpretation and diagnosis of urban functional mix.

Space syntax analysis of the city as a movement economy has made major contributions to our understanding of the spatial structure of cities, particularly the importance of a mapping of network integration in relation to density, functional mix and streetlife vitality. It has focused attention of urban researchers onto the importance of the relations between the sociality and spatiality of the city. The primary methods of syntactic analysis involve a reduction of urban morphology to a set of spatial axes; here, we explore some limits to such analysis for urban design. Topological analysis of axial models has long recognized problems in accounting for distance, scale and sinuous streetscapes. Existing adaptations to axial methods that address such problems are modelled and shown to produce a broad range of results for the same urban morphology. In each case, we also compare different capacities for to-movement and through-movement – the distinction between ‘closeness centrality’ and ‘betweenness centrality’ that shows that network integration is multiple. We argue that axial analyses privilege visibility over accessibility and can produce distorted mapping at walkable scales; only one of the methods tested measures permeability and walkable access. Space syntax analysis is a powerful tool that will be more useful the better such limits are understood.

URBAN DESIGN International is a scholarly publication with a strong practitioner emphasis. It is relevant for all of those involved in architectural and planning education and practice. It is relevant for urban designers, architects, planners, surveyors and landscape architects and all professionals concerned with urban development and design.

The relationship between urban morphology and walkability is central to urban design theory and practice. In this paper, we develop new measures for pedestrian permeability and catchment areas, suggesting that their joint use can progress our understanding of the ways urban morphology mediates walkability. Existing measures of permeability do not account for heterogeneous morphologies. Likewise, measures of pedestrian catchment do not account for what it is that is caught. The proposed “area-weighted average perimeter” and “interface catchments” together integrate both street width and block size, measuring both walkable access and what one gets access to. What is at stake is not only correlations with health and transport, but also measures of walkable access that are geared to the social and economic productivity of the city.