<p>Support data ISS-en light.</p>

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.</p></div>