Even though the prerequisites are such that winter road maintenance should be possible to perform according to the requirements in the "General technical description of road operation service levels during winter", it still happens that the road conditions are considerably worse than intended. A number of "mishaps" leading to incidents and accidents occur each winterseason. In the mid 1990s an investigation of police reported skidding accidents commissioned by the Swedish National Road Administration (SNRA) wasperformed. It became apparent that maintenance measures were carried out surprisingly late even though the situations with slippery conditions should have been predicted in good time with available technical support (for example RWIS). It also appeared that the tyres on the vehicle involved in the accidents often were very bad. Since then alternative ways of performing an evaluation of the winter road maintenance have been discussed at several occasions. Recently a new project commissioned by the SNRA was carried out. In this case the so-called Winter Measuring Vehicle (WMV) was used to follow up the winter maintenance measures on a few selected road sections. It has equipment for automatic registration of winter road conditions such as air and road surface temperature, air humidity, friction, snow depth and freezing point. The evaluation was based on the data from measurements with the WMV, except for snow depth due to unsatisfactory performance of this equipment. Information on winter maintenance measures and what thedecisions were based on was also gathered. In addition weather data and forecasts from the RWIS system were used for the evaluation. The measurements with the WMV should primarily indicate whether the requirements for winter road service levels were fulfilled or not. If this was not the case itwas investigated if any measures had been carried out and if so, which these were. Furthermore, it was investigated on which information the decisions for winter maintenance measures should be carried out were based, or alternatively why measures had not been carried out at all. It can also happen that measures are carried out too late for various reasons, for example incorrect forecasts or problems with equipment. In brief it was found that preventive measures (salting) are mostly carried out satisfactorily. However, at several occasions forecasts have indicated a risk of slipperiness which then never occurred, resulting in unnecessary salting. It was often found to be difficult to fulfil the requirements on maximum allowed snowdepth during snowfall. Also, the personnel requested more reliable forecasts and information about residual salt. For the covering abstract see ITRD E143097.
Abstract