ESP (Electronic Stability Programme) has recently been introduced on the market to reduce the number and severity of loss-of-control accidents. It has been expected that this reduction would mainly be addressed to accidents on roads with low friction. It is, however, complicated to evaluate the effectiveness with more conventional methods.

In this study, data from accidents occurring in Sweden during 2000 to 2002 were used to evaluate the effectiveness of ESP. To control for exposure, induced exposure methods were used, where ESPsensitive to ESP-insensitive accidents and road conditions were matched in relation to cars equipped with and without ESP. Cars of similar or in some cases identical make and model were used to isolate the role of ESP.

The study shows that there are positive effects of ESP in circumstances where the road has low friction. The overall effectiveness was 22.1 +/- 21 %, while for accidents on wet roads, the effectiveness was 31.5 +/- 23.4 %. On roads covered with ice and snow, the corresponding effectiveness was 38.2 +/- 26.1 %. ESP was found to be effective for three different types of cars, small front wheel drive, and large front wheel and large rear wheel drive cars.