Introduction We aimed to assess the impact of introduction of a dedicated trauma surgical unit (TSU) on CT utilisation for polytrauma in the Emergency Department (ED). Methods Single centre retrospective cohort study comparing adult patients undergoing CT for polytrauma following TSU introduction (Intervention group, n = 617) to a historical Baseline group (n = 257) over a matched time period. Patient impact, including initial clinical assessment, injuries, radiation exposure, incidental findings, ED disposition, and impact on radiology services were compared with Mann-Whitney and Fisher's exact tests. Results Intervention patients were more likely to be examined by ED physicians (96.7% vs. 91.1%, p = 0.001) prior to CT. There was greater documented clinical suspicion for chest and abdominal injuries, with increased WBCT utilisation for Intervention (Baseline 17.1% vs. 47.8%, p < 0.05), with no significant increase in positive scans by region. More CT chest (Intervention 38.4% vs. Baseline 14.8%, p < 0.05), CT abdomen (42.6% vs. 12.6%, p < 0.005) and CT pelvis (46.1% vs. 16%, p < 0.001) was performed even with low documented clinical suspicion, with no significant increase in positive findings. The intervention group returned for more additional scans (12.48% vs. Baseline 5.45%), had more incidental findings (23.66% vs. 15.18%), and were more likely to be admitted for observation (21.7% vs. 14%), all p < 0.05. Time to scan and total CT reporting time were significantly longer for Intervention. Conclusion Introduction of a TSU was associated in a shift towards increased CT utilisation, with no increase in scan yield, increased incidental findings and impacts on Radiology workflow.