Predicted effect of automatic crash notification on traffic mortality

Abstract

Objective: To estimate the reduction in traffic mortality in the United States that would result from an automatic crash notification (ACN) system. Methods: 1997 Fatality Analysis Reporting System (FARS) data from 30875 cases of incapacitating or fatal injury with complete information on emergency medical services (EMS) notification and arrival times were analyzed considering cases at any time to be in one of four states: (1) alive prior to notification; (2) alive after notification; (3) alive after EMS arrival; and (4) dead. For each minute after the crash, transition probabilities were calculated for each possible change of state. These data were used to construct models with (1) number of incapacitating injuries ranging from FARS cases up to an estimated total for the US in 1997; (2) deaths equal to FARS total; (3) transitions to death from other states proportional to FARS totals and rates and (4) other state transitions equal to FARS rates. The outcomes from these models were compared to outcomes from otherwise identical models in which all notification times were set to 1 min. Results: FARS data estimated 12 823 deaths prior to notification, 1800 after notification, and 14 015 between EMS arrival and 6 h. If notification times were all set to 1 min, a model using FARS data only predicted 10 703 deaths prior to notification, 2306 after notification, and 15 208 after EMS arrival, while a model using an estimated total number of incapacitating injuries for the US predicted 9569 deaths prior to notification, 2261 after notification, and 15 134 after arrival. In the first model, overall mortality was reduced from 28 638 to 28 217 (421 per year, or 1.5%), while in the second model mortality was reduced to 26964 (1674 per year, or 6%). Conclusions: Modest but important reduction in traffic mortality should be expected from a fully functional ACN system. Imperfect systems would be less effective.