Introducing PtAC – an open source tool to assess SDG 11.2 using open data

Abstract

This paper presents a novel approach for assessing and monitoring Sustainable Development Goal 11.2.1, which measures the proportion of an urban population having convenient access to public transport. Despite its global importance as the key indicator for urban mobility, many cities face significant barriers to implementation, including limited access to standardized input data and a lack of technical capacity. To address these challenges, we introduce PtAC, the Public Transport Access Calculator, an open-source Python library that combines remote sensing data from the World Settlement Footprint Population with crowdsourced geospatial data from OpenStreetMap. PtAC automates the calculation of SDG 11.2.1, offering a globally applicable, transparent, and reproducible methodology for consistent monitoring of urban transport accessibility. The tool was applied to 33 cities worldwide, and its outputs were validated against reference data provided by UN-Habitat. Validation results show a high correlation, underscoring the tool’s potential to support scalable SDG monitoring. The study demonstrates how open and remote sensing data can be operationalized to bridge existing methodological gaps in urban sustainability assessments.