The energy transition is increasing pressure on utility infrastructure projects to be delivered efficiently and at scale. At the same time, integrated delivery approaches are transferring greater design responsibility to contractors, creating opportunities to incorporate construction knowledge earlier in the design process. However, constructability assessments remain largely informal and experience-based, leading to inconsistent evaluations and a risk of overlooking construction challenges. This paper investigates how geospatial technologies can support a more systematic assessment of constructability during the engineering stage of low-voltage utility network projects. Using a Design Science Research approach, a GIS-based Decision Support System (DSS) was developed that formalises constructability knowledge into explicit spatial assessment rules. The prototype combines urban spatial data and project-specific design information to assess route feasibility, workspace requirements, and construction-method constraints. Through rule-based spatial analysis, the system identifies hard, soft, and workflow clashes between proposed cable route designs and their surrounding environment. Demonstration on a real-world project and evaluation with industry practitioners indicate that the approach supports more consistent and transparent identification of constructability issues. The results demonstrate the potential of GIS-based decision support to bridge the gap between experience-based engineering practice and data-driven constructability assessment.