Timeliness and trauma: Quantifying the impact of EMS response delays on crash fatality risk.

INTRODUCTION

Timely Emergency Medical Services (EMS) response is a critical determinant of survival following motor vehicle crashes, yet its quantitative impact remains underexplored in transportation safety research.

METHOD: This study analyzes 10 years of linked Florida crash and EMS data (2014-2024; fatal and incapacitating injury; n = 7187) to quantify how EMS arrival time is associated with fatality risk under observed covariate adjustment, accounting for triage bias-where severe crashes receive faster responses but exhibit higher mortality. We apply complementary methods including descriptive profiling, logistic regression with restricted cubic splines (RCS), propensity score matching (PSM), and interpretable machine learning (Extreme Gradient Boosting (XGBoost) with SHapley Additive exPlanations(SHAP)). Results reveal steep survival gains with faster response within the first 5-10min, diminishing returns thereafter, and critical vulnerability windows at 7-15min for severe crashes and 25-35min for less severe crashes.

RESULTS

Heterogeneity analyses show that the benefits of rapid response vary by age, sex, and speed, with older occupants and high-speed crashes gaining the most. Across designs, EMS minutes rank among the top predictors of fatality risk, second only to speed.

CONCLUSIONS AND PRACTICAL APPLICATIONS: Findings underscore the need for dispatch optimization, rural coverage improvements, and adaptive prioritization strategies to reduce early response delays and advance equity in trauma care.