<p>It is important to understand the effects of explosions to ensure the safety of civilians and military personnel. Rapid City Planner (RCP) is a comprehensive software tool for predicting the effects of conventional and improvised explosive devices with geographic information system-based outcomes for munition safety, building/structure damage, protection of assets, and human vulnerability in real cities. Modelling cased explosives requires the consideration of casing fragmentation, which is modelled in RCP using three different methods having a different level of detail. The present study focuses on introducing and validating one of the methods, namely the fast primary fragmentation method. The fast fragmentation solver is used to simulate casing breakup of steel-cased cylindrical charges with various TNT- and RDX-based explosives. The predicted velocities were within less than one percent of theoretical Gurney velocities, and the fragment size distributions compared well with experimental data for each explosive. A TNT-filled artillery shell trial was used to validate the fast fragmentation solver in terms of polar distributions of initial fragment speed and number, as well as the spatial spread of fragment throw in a free-field environment. The RCP hydrocode solver is used to assess the equivalent bare charge model used by the fast fragmentation approach. The detailed and fast-modelling approaches produced similar peak overpressures, but underpredicted impulses, at standoff distances between 5 and 10&#xa0;m (mid-to-far field range). The failure strain and fragment size distribution are shown to have little effect on the blast wave, whereas both would have a significant impact on subsequent fragment effects. Finally, a full-scale scenario was modelled in RCP to show blast and primary fragmentation effects in a coastal urban environment, including a demonstration of urban blast effects from blast pressure and primary fragment trajectories outcomes.</p>