The Effect of Earlier or Automatic Collision Notification on Traffic Mortality by Survival Analysis

OBJECTIVE: This article explores the effects of earlier emergency medical services (EMS) or automatic collision notification (ACN) and EMS arrival on passenger/driver survivability within the short time frame following traffic crashes. METHODS: Survival analysis techniques are used extensively in this study, because traffic crash and EMS data are closely associated with time. The Kaplan-Meier estimator and life curves are applied to compare the survival rates between 2 or more conditions (e.g., earlier verus late EMS notification); The Weibull model with 3 parameters is used to predict mortality over time; furthermore, the Cox proportional hazard model explores multiple risk factors related to traffic mortality. RESULTS: Based on Fatality Analysis Reporting System (FARS) data from 2005 to 2009, Kaplan-Meier life curves clearly showed the benefits associated with earlier notifications (approximately 1.84% fatality reduction within a time frame of 6 h after a crash) and earlier arrivals, and the Weibull model with 3 parameters reasonably predicted the fatality trends. The relative risks (RRs) associated with collision notification, arrival, location, and age were obtained from a multiple Cox regression model, and the relatively higher fatality hazard (2.4% higher) associated with the later notification of more than 1 min was studied in detail. CONCLUSIONS: This article obtains the driver/passenger survival probability differences over time under different conditions of collision notifications, EMS arrivals, and crash locations; furthermore, this analysis provides an estimation of the lives that could potentially be saved (approximately 154 to 290 per year) due to earlier ACN.