Understanding the impact of urban infrastructure on perceived road safety is crucial for improving children's road safety. This study explores the relationship between the built environment and perceived safety using a novel combination of subjective perception data and geospatial data. Perceived safety assessments were gathered through the Route2School (R2S) application, which collects crowdsourced inputs from schoolchildren and their guardians. These inputs were linked with detailed road infrastructure data from OpenStreetMap (OSM) across four cities in Flanders, Belgium: Antwerp, Gent, Mol, and Zonhoven. The study's findings reveal both universal and city-specific determinants of perceived safety. While road type, presence and type of intersection, and bicycle infrastructure emerged as common influential features, their importance varied across the urban contexts. The approach presented here demonstrates how integrating crowdsourced data with open-source spatial information can support child-centric urban design and targeted policy actions to enhance perceived traffic safety and mobility. The insights gained from this study can inform data-driven planning and policy-making aimed at creating safer, more inclusive urban environments for vulnerable road users.