PURPOSE: Trauma Triage Tools (TTTs) support pre-hospital staff to identify major trauma patients based on prehospital characteristics and bring them to appropriate trauma centres. However, while triaging trauma has been examined extensively, there appears to be little consensus on how variables within TTTs are applied. We therefore aimed to examine the prehospital characteristics and their operationalization applied in the international literature in TTTs. METHODS: We applied a hybrid systematic review approach. Searches were conducted in multiple databases. We initially searched for systematic reviews that analyse prehospital characteristics applied in TTTs, then supplemented this with an updated search of original TTT papers from November 2019. RESULTS: We identified 92 papers which identified 52 adult general population TTTs. Results indicate considerable heterogeneity in prehospital characteristics included in TTTs internationally. There was similarity in the higher-level categories included in the tools: tools often included measurements of a patient's physiological characteristics, injury characteristics, mechanism of injury and any modifiers for high-risk groups. However, the prehospital characteristics that made up those groups, how they were applied and interpreted were found to vary considerably. CONCLUSION: While there is agreement in the higher-level categories used in TTTs, the thresholds adopted in specific variables vary widely, which may reflect statistical rather than clinical considerations. This may contribute to considerable variation in standards of major trauma triaging internationally. An agreed taxonomy of operationalization of prehospital characteristics used in TTTs is required to prevent sub-optimal clinical decision-making in major trauma triaging. REGISTRATION: PROSPERO CRD42023393094.