Description of the TARVA program

TARVA: A TOOL FOR ESTIMATION OF TRAFFIC SAFETY EFFECTS OF ROAD IMPROVEMENTS

Software for the estimation of safety effects of potential road improvements was developed at the Technical Research Centre of Finland (VTT) for the Finnish National Road Administration (Finnra).

The method uses road, traffic and accident information and the latest knowledge of the effects of different safety measures. This information is maintained in a database wherefrom the user can select the road section and safety measures for investigation. The main phases of the estimation procedure are: 1) determination of the present level of safety and 2) application of coefficients to describe the effect of improvements.

The present level of safety is determined by combining recent accident data of the particular road section and information of the average safety of similar road conditions in general. This is conducted by employing Empirical Bayesian methods. Accidents of motor vehicles and pedestrians/ bicyclists are assessed separately.
If planned road improvements take place in the future, the present level of safety can be projected into any target year.

The impact on injury accidents is then computed by application of pre-determinated coefficients. These coefficients have been defined by critical review of latest research.

The effects of more than 60 potential road safety measures are currently available. Moreover, the procedure takes into account the changes in the severity of accidents. Several safety measures may be applied simultaneously.

The safety effects of the measures are given as expected changes in numbers of accidents and fatalities. The results may be presented in various ways, depending on the needs of the user. The system allows the presentations of results from several road sections in a single report.