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Societies aim to reduce primary raw material consumption, enhance waste recycling, and reduce waste disposal. In this regard, the circular‐economy concept has gained attention and is applied in policy papers, also on the urban level. However, to assess set targets and their achievement, a sound knowledge of anthropogenic material flows and stocks is required. The material turnover of transport systems has not been sufficiently investigated yet, although they have a significant impact on overall material turnover and have a high potential for making use of recycled construction materials. To close this gap, the present study investigates the anthropogenic stocks and flows related to an urban transport system, whereby both infrastructure and vehicles are included. A bottom‐up, multiyear material‐flow analysis was employed to calculate the material stock and the related input and output flows of Vienna's transport system for the period 1990–2015. The results indicate the increasing importance of more environmentally friendly modes of transport. The stock of motorized individual transport has increased in absolute terms since 1990, but the stock per capita remains unchanged at 34 t/cap, whereas the per capita stock of public transport (20 t/cap; +8%) and of non‐motorized individual transport (4 t/cap; +10%) has increased. However, the primary source of material consumption (>65%) is maintenance of infrastructure. This provides a potential for more circularity because outputs and inputs are equal in terms of mass and material. The study provides a systematic analysis for developing policy and management options for sustainable resource‐saving urban transport systems.

Population growth in cities leads to high raw material consumption and greenhouse gas emissions. In temperate climates were heating of buildings is among the major contributors to greenhouse gases, thermal insulation of buildings became a standard in recent years. Both population growth and greenhouse gas mitigation may thus have some influence on the quantity and composition of building material stock in cities. By using the case study of Vienna, this influence is evaluated by calculating the stock of major building materials (concrete, bricks, mortar, and plaster, steel, wood, glass, mineral wool, and polystyrene) between the years 1990 and 2015. The results show a growth of the material stock from 274 kt in the year 1990 to 345 kt in the year 2015, resulting in a total increase of 26%. During the same period, the population grew by 22%. On a material level, the increase of thermal insulation materials like polystyrene and mineral wool by factors of 6.5 and 2.5 respectively were much higher than for other materials, indicating energy efficiency and greenhouse gas mitigation in the building construction sector. The displacement of brickwork by concrete as the most important construction material, however, is rather a response to population growth as concrete buildings can be raised faster. A question for the future is to which extent this change from brickwork to high carbon-intensive concrete countervails the achievements in greenhouse gas reduction by thermal insulation.

Many studies calculate the material stock of buildings by using material intensities and reference values for building dimensions. Often, they lack a clear definition of and transparency in the selection of buildings to be analyzed, as well as adequate description for the determination of the material intensities of buildings. This article presents a randomized selection of buildings and determination of their material intensities using the case study of Vienna. On the basis of a digital geo-information building model, buildings were categorized according to their age, use, and volume. From each category, samples were randomly selected and their material intensities as well as different building dimensions were determined based on building documents such as plans. The building dimensions were used to express the material intensities related to different reference values. The 256 objects analyzed correspond to a sample size of 0.11% relative to the total number and 0.22% relative to the total gross volume of objects in Vienna. Although the total material intensities were comparable to other studies, the material intensities of insulation materials in older buildings were found to be higher in this study because of a higher representativeness of the data used. In addition, the expression of the material intensities related to different reference values such as area or volume of buildings improved comparability with other studies. Nevertheless, further research is required, particularly concerning the selection of representative samples of buildings.

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