What densities? Using urban density metrics to reflect meaning in policy and planning action

Abstract. Urban density has been a pivotal concept in political discourses to address the global challenge of sustainable and equitable urban development in the past decades. Consequently, policy and planning strategies have focussed on creating denser neighbourhoods. However, empirical knowledge on the effects of such policies on produced urban form and densities created remains vague, leading to limitations of evaluating them in accordance to their sustainability goals. Therefore, this contribution introduces a regional cross-border settlement model that allows to analyse effects of land policy in urban form comparatively between France and Germany. As many policies promote urban density, we take the case of a specific French land policy, the loi SRU, that aims at generating more social housing and dense urban environments. Based on the developed settlement model, containing information on building type and block age, we test and select different density metrics to assess the evolution of urban form. We compare the share of building types as well as density across national context, building types and development ages to describe the effects of the policy. 
The results highlight the general applicability of the settlement model, as we could show and interpret the share of multi-family housing being elevated in the French part, while it decreases in the German part. Further, selected density metrics show that new construction in France maintains density, while in Germany density is decreasing. Further research is required to enhance the settlement model through considering location and infill development to enhance the analytical capabilities.