Form Follows Policy

Problem Statement
The built urban form is a crucial aspect for the sustainable development of cities and regions. It not only influences emission-intensive patterns of behaviour - such as reliance on motorised private transportation - and leads to a decline in biodiversity through land use, but it also determines the efficiency and effectiveness of climate adaptation measures. Focusing on the built environment is therefore a key component of sustainability strategies. These strategies give rise to concrete policy measures at the national level and in municipalities; such as funding programs, planning guidelines, or taxes that aim to influence built urban form.

While such policy measures are implemented to promote sustainable urban development, our understanding of their actual impact on spatial development remains vague and is often overlooked. It is therefore necessary to examine the causal relationships between sustainability-oriented land policies and the built urban form.

Aims
The availability of geospatial data in a standardized and comprehensive format, as well as the development of data-driven approaches - such as machine learning approaches - make it possible to analyse urban-regional structures on a large scale. At the same time, the political discourse on urban sustainability has been ongoing long enough that the effects of policy measures should now be perceptible and measurable in the built urban form. The project therefore employs a mixed-methods approach that combines geodata analysis with the analysis of land policy measures.

For this purpose, a comparison is made of urban structures in the French-German border region and of the different policy measures pursued in the two countries. The functional regions of Strasbourg and Karlsruhe serve as the study area. Given their similar cultural, demographic, and economic development over the recent decades, the focus can be placed on the two different land policy and planning systems. The aim is to understand and describe the causal relationships between policy measures and the resulting urban form.

This gives rise to follow-up questions, which are addressed in the individual phases of the project.

Project Contents
The project is divided into three phases. In the first phase, the urban form in the two countries will be analysed and emerging patterns of urban form will be compared against the backdrop of differing land policy measures. To this end, a geodata model will be established to identify urban development projects in five-year intervals between 1990 and 2020. These urban development projects will then be analysed and compared with regard to the characteristics of their urban form. In this phase of the project, emerging patterns of urban form between the two countries will be identified and interpreted in the context of the relevant national policy measures.

Subsequently, sustainable land policies from the period under investigation will be identified and their various mechanisms of action analysed. A neo-institutional perspective on the various practices of sustainable land policy enables an understanding of the underlying mechanisms and modes of operation in decision-making processes. By examining the data over time, the aim is to identify the causal links between such policy measures and the findings of the first phase of the project.

Finally, selected urban development projects in the two countries will be examined in greater detail, and the underlying institutional logics of sustainable urban development will be analysed. The focus here is on the question of what influence policy measures have had on the individual decision-making process regarding the chosen urban form, and whether these measures have been conducive or an obstacle to sustainable spatial development.

Results
Key methodological findings include a workflow for a cross-border urban form model for the study area. This harmonises German and French geodata, thereby enabling analyses ranging from individual buildings and blocks to neighbourhoods, sub-areas to the entire region. Building on this foundation, Kleiner und Jehling (2026) establish a link between changes in land use and planning policy and changes in urban form. This facilitates a discussion of policies in relation to their objectives for sustainable urban development. Urban form can thus be examined quantitatively and spatially at both local and regional levels. Crucial to this is the description of urban form within the context of functional urban-regional interconnections in the border region (Jehling et al., 2026). In general, this allows for a comparative analysis of the relationship between sustainability strategies and the built environment in Germany and France, without neglecting the specific context within the urban-regional situation. This means that urban form can be evaluated in terms of its functional location (more urban and easily accessible, or peripheral and less easily accessible). The urban form model is published as open-source code.