Infrastructure operators face a common challenge: planning, construction and maintenance of road and rail networks require current, reliable as-built data – ideally captured without interrupting live operation. Drawing on completed road and rail projects, this talk shows how modular mobile mapping systems (including the Trimble MX9) capture dense, high-precision point clouds and high-resolution imagery in a single pass at up to 100 km/h – without track closures and, on the rail side, based on a Deutsche Bahn product approval under Ril 883.6000. The focus is on how this data turns into concrete decisions: alignment and clearance-gauge data for planning, AI-based automatic asset detection for inventory databases, and BIM as-built models and digital twins for operation and maintenance. Using examples such as the capture of several thousand route kilometres and selected rail and motorway projects, the presentation covers achievable accuracies, the workflow from raw capture to decision-ready model, and the economic comparison with conventional methods. It addresses infrastructure operators, surveying and engineering firms and BIM/digital-twin owners.