Assessing the efficiency of indoor and outdoor access-related infrastructure

How does urban density affect the efficiency of access infrastructure? A novel approach considers both 'outdoor' and 'indoor' access infrastructure. A hypothesis is developed and tested to determine if spatial costs shift from 'outdoors' to 'indoors' in rising building densities. Taking into account the significance of theoretical research and its impact on decision-making practices on development, a case study in a Chinese city is conducted to assess the spatial costs of building-internal and building-external access for different types of residential neighbourhoods, thereby exploring the relationship between the number of floors and accessibility costs in terms of area consumption. Three different types of residential neighbourhood representing diverse density situations are analysed and evaluated. Although based on a single case study, the results provide valid arguments to substantiate the shift hypothesis. The findings challenge the existing planning notions regarding gains in infrastructural efficiency and instead show reduced efficiencies can occur in high-density development when indoor access is taken into account. Under comparable factors of access quality, compact settlements may even display lower efficiencies than less compact areas. These considerations indicate the need for a more critical and wider view of the efficiency gains provided by dense settlement forms. Policy relevance When building densities increase, the burden of spatial costs for access infrastructure (mobility, traffic access, vertical circulation and parking) shifts from 'outdoors' to 'indoors', potentially increasing in overall terms. This challenges current ideas in urban planning that higher density leads to gains in infrastructural efficiency. Economic and resource efficiency are clearly reduced when indoor access is taken into account. Indeed, under comparable factors of access quality, compact settlements may have lower efficiencies than less compact areas. These new insights indicate the need for a more critical and wider reappraisal of the efficiency gains provided by dense settlement forms, particularly high-density and high-rise residential development. Developers, planners and designers will need to develop new processes and guidance for evaluating efficiencies of urban settlement and their sustainability.