A macro-analysis of impacts of safety interventions on road safety developments in a country

This research focused on examining the over-time developments of road safety in Israel, in order to identify the time points at which positive changes occurred, i.e. a decrease in the number of road accident fatalities, injuries or accidents, taking into account the changes observed in exposure. The time points found with a positive change - a decrease in risk level, i.e. the number of fatalities/ injuries/ accidents related to exposure, allowed to identify the safety interventions which were implemented in proximity to these time points and, therefore, probably contributed to the improvement of the level of safety.As a first stage in the research, an extensive mapping of safety interventions in Israel, for the years 1970-2008, was conducted. Among the safety interventions considered were: changes in transportation regulations regarding safety vehicle accessories, restrictions to young drivers, enhancement of the regulations for driving under the influence of alcohol, as well as significant improvements in road infrastructure, large-scale enforcement operations, vehicle improvements, improvements in the rescue services, etc.The examination of road safety developments in Israel was performed by means of fitting statistical models both for general series of the numbers of casualties and for more detailed series such as: fatalities on urban and rural roads, pedestrian fatalities, fatalities and serious casualties among young drivers, fatal and serious single vehicle accidents, fatalities and casualties in light vehicles. As exposure estimators were used: vehicle-kilometers traveled and their substitutes, e.g. the number of registered vehicles in the country, the number of private vehicles and the population size. In total, 45 casualty series with relation to exposure estimators were analyzed.Two methods were applied for fitting the models: (a) describing the over time development of the risk rate (casualties/ accidents divided by exposure), using "broken-line regression" models. Having the models fitted, the meanings of the break-points found were examined; (b) Fitting "structural time-series" models. These models are used to estimate the components of the level and slope of the linear trend local model and model's residuals, while controlling for known explanatory variables (e.g. the exposure). Using these models, forecasts from specific time-points on were produced, and differences between what would be expected to be the development of the series and the actual counts were examined. The time-points for the forecasts were determined based on former knowledge regarding the timing of the introduction of major safety interventions.For most of the positive changes in safety developments in Israel which were identified using the models, relations to the safety interventions implemented in time proximity to the changes were suggested.