Background: Metrics exist to assess and validate trauma system outcomes; however, these are clinically focused and do not evaluate the appropriateness of admission patterns, relative to geography and triage category. We propose the term “functional inclusivity” defined as the number and proportion of triage-negative, and/or nonseverely injured patients, who were injured in proximity to a level II/III trauma center but admitted to a level I facility. The aim of this study was to evaluate this metric in the North West London Trauma Network. Methods: Retrospective, geospatial, observational analysis of registry data from the North West London Trauma Network. We included all adult (≥16 years) patients transported to the level I trauma center at St. Mary's Hospital between 1/1/13-31/12/16. Incident location data were geocoded into longitude/latitude, and drive times were calculated from incident location to each hospital in London's Trauma System, using Google Maps. Results: Of 2051 patients, 907 (44%) were severely injured (injury severity score [ISS] ≥15), and 1144 (56%) were nonseverely injured (ISS 1-15). Seven hundred ninety five of the 1144 nonseverely injured patients (69%) were injured in proximity to a level II/III but taken to the level I facility. A total of 488 (24%) patients were triage-negative, and 229 (47%) of these were injured in proximity to a level II/III, but taken to the level I trauma center. Conclusions: This study has demonstrated the concept of functional inclusivity in characterizing trauma system performance. Further work is required to establish what constitutes an acceptable level of functional inclusivity and what the denominator should be, as well as validating and further evaluating the concept of functional inclusivity.