City and regional planners have recently started exploring a circular approach to urban development. Meanwhile, industrial ecologists have been designing and refining methodologies to quantify and locate material flows and stocks within systems. This Perspective explores to which extent material stock studies can contribute to urban circularity, focusing on the built environment. We conducted a critical literature review of material stock studies that claim they contribute to circular cities. We classified each article according to a matrix we developed leveraging existing circular built environment frameworks of urban planning, architecture, and civil engineering and included the terminology of material stock studies. We found that, out of 271 studies, only 132 provided information that could be relevant to the implementation of circular cities, albeit to vastly different degrees of effectiveness. Of these 132, only 26 reported their results in a spatially explicit manner, which is fundamental to the effective actuation of circular city strategies. We argue that future research should strive to provide spatial data, avoid being siloed, and increase engagement with other sociopolitical fields to address the different needs of the relevant stakeholders for urban circularity.

Transit-Oriented Development (TOD) is an urban planning approach that encourages a modal shift from private to public transportation. This shift can generate additional benefits from a sustainability perspective. This study aims to assess the efficiency of TOD by applying the data envelopment analysis (DEA) method. The ridership of public transportation is considered as the direct output characteristic of TOD efficiency, and nine indicators of ridership are selected as inputs on the basis of the core concepts of TOD. These concepts include density, diversity, and design (3Ds). The Tokyu Den-en Toshi Line in Japan is presented as a typical case of TOD because this line includes TOD and non-TOD stations. Assessing and comparing the results of all railway stations reveal that almost all indicator values of non-TOD stations are higher than those of TOD stations. The results suggest that TOD planning and programs are inefficient in terms of ridership generation. This implication, however, may be attributed to the inadequacy of the selected indicators for TOD assessment. The results obtained after adding operation year as input indicators and removing transfer station show that TOD stations perform efficiently and in accordance with expectations. This response indicates that the inclusion of influential factors is necessary for equitable TOD assessment. Therefore, other influential factors must be considered when evaluating the efficiency of TOD-based stations with different inherent attributes. In addition, the design input with the largest impact on all inefficient units was identified, suggesting that management of bus service and railway system should be well enhanced.