Applying data envelopment analysis to evaluate efficiency of low emission zone policies in European cities

Low emission zones (LEZ) have been widely adopted in Europe, evolving through iterative refinements to enforce stricter access criteria and align with sustainable urban transport objectives. A substantial body of literature examines the efficacy of LEZs, encompassing the environmental and social effects of LEZs, while little attention has been paid to evaluating their overall efficiency from a quantitative, multi-criteria perspective. This study introduces Data Envelopment Analysis (DEA) to assess the performance of 12 European cities with diverse socio-economic and transport characteristics. The analysis incorporates three inputs (GDP/capita, LEZ ratio, and access strictness) and three outputs (two pollutants and the compliance rate) to capture the comprehensive efficiency of LEZs. All analyses were conducted by DEAP software, adopting an output-oriented approach. The results highlight the effectiveness and practicality of DEA in evaluating LEZ efficiency. Furthermore, Munich, Milan, Stockholm, and Brussels are found to be below the efficiency frontier, for which targeted improvement recommendations are proposed The main limitations of this paper are data availability and time inconsistency, which were mitigated through logical imputation and interpolation to estimate the missing data.