Road Setback Management System: A Web-Based GIS Tool for Screening Building Setback Compliance along Roads in Lusaka

Road reserves and building lines protect the space that roads need for future widening, drainage, utilities, sight distance and safety. In Lusaka, rapid urban growth has made encroachment of buildings into these setbacks a persistent development-control problem, while enforcement still depends largely on manual site inspection, paper records and case-by-case interpretation of the applicable distance. This project set out to design and implement a web-based Geographic Information System (GIS) tool that helps enforcement officers screen buildings along a selected road for possible setback violations. An iterative, Agile-inspired development approach was followed. The resulting Road Setback Management System consists of a Next.js web client with a Leaflet map, an Express/Node.js GIS service, and a Supabase (PostgreSQL/PostGIS) database. Setback rules are held as configuration data rather than code: each OpenStreetMap road class is mapped to a regulatory class with a default distance (30.48 m, 18.288 m or 9.144 m), which can then be overridden by road-wide assignments and by structure, parcel or road-segment exceptions through a deterministic precedence procedure. Candidate buildings near the selected road are retrieved with a PostGIS spatial query, the shortest distance between each footprint and the road centreline is measured with Turf.js, and each building is classified as compliant, non-compliant or unknown. Every result records the rule that produced it and is flagged for human verification. Inspection runs are stored with an audit history, and administrators can review candidate status and manage user roles under row-level security. The system was evaluated with 31 automated test cases covering rule resolution, geometric measurement, compliance evaluation and end-to-end candidate assessment using synthetic geometry with known distances. Twenty-nine tests passed and two exposed genuine defects (an exception-precedence tie check and an obsolete module entry point), which are documented together with further issues found through code review. The assessment engine processed 1,000 candidate buildings in about 0.33 s (≈0.33 ms per building). The project shows that configurable, explainable, open-source GIS screening is a practical first step towards more consistent and efficient road setback enforcement, provided that its outputs are treated as screening results that require field verification.