Vulnerable road user fatalities are associated with greater trauma: Long-term autopsy-based trends in Czechia (1969–2024)

Traffic accidents are an inherent consequence of modern transportation and mobility systems. Changes in the post‑crash care system over the past fifty years may have influenced the survival prospects of injured vulnerable road users (VRUs) involved in traffic accidents. We therefore focused on assessing injury severity among fatally injured VRUs in Czechia. We analysed Injury Severity Scores (ISS) derived retrospectively from autopsy documentation (medical autopsy reports and forensic expert opinions) for a random sample of 15 deceased pedestrians and cyclists from each selected year (every fifth year) between 1969 and 2024 who underwent autopsy at Olomouc University Hospital (Czechia). We focused on trends in the first quartile of ISS values and applied a non‑parametric trend analysis to determine statistical significance. There was a statistically significant upward trend in the first quartile of ISS values over the study period, indicating an upward shift in the lower tail of trauma severity among fatal cases. One possible interpretation is that less severely injured VRUs may have become less represented among fatalities over time; however, this pattern cannot be attributed directly to improvements in post-crash care. It may also reflect changes in crash severity, exposure patterns, case mix, referral pathways, reporting practices, or documentation. Accordingly, Q25 ISS should be interpreted only as an indirect, hypothesis-generating proxy compatible with long-term changes in survivability, not as direct evidence that post-crash care improved.