• Jingshu Wu, Rajesh Subramanian, Matthew Craig, Marc Starnes, and Anders Longthorne.
• National Highway Traffic Safety Administration, U.S. Department of Transportation, Washington, DC, USA. jingshu.wu@dot.gov
• Traffic Inj Prev. 2013 Jan 1; 14 Suppl: S50-7.

ObjectiveThis 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.MethodsSurvival 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.ResultsBased 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.ConclusionsThis 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.

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