Background: To assess the effect of the Demerit Point System (DPS), introduced in Spain on 1 July 2006, on the number of fatalities due to road traffic accidents, using a methodology that controls for the seasonal variation and trend in the data series.
Methods: Time-series analysis by ARIMA models of 29 113 fatalities in road traffic accidents (at the accident scene or within 24 h thereafter), between January 2000 and December 2007. The model permitted estimation of an intervention parameter, together with its 95% CI, to calculate the number of fatalities that would have occurred if the DPS had not been implemented, after controlling for the effect of other measures introduced in 2004.
Results: It was estimated that 618 persons (95% CI 259 to 977) would have died in traffic accidents in the 18 months after implementation of the DPS had it not been in effect, which represents a reduction of 14.5% (95% CI 6.1% to 23.0%) from a total of 4252 deaths.
Conclusion: Implementation of the DPS in Spain has led to a significant reduction in the number of traffic accident deaths in the context of a downward trend after the implementation of the 2004 measures.