Previous investigations focusing on interdependences between the concentration of de-icing salt and its persistence on road surfaces have only been conducted on highways. However, volumes of traffic, the dispersion of traffic and vehicle speeds differ remarkably between highway roads and non-highway roads. Hence, up to the present day, it has not been possible to adapt current insights for roads of the latter type. During the winter seasons 2011/2012 and 2012/2013, measurements have been executed on 13 different road sections in Germany. The road sections vary in terms of their geographic location (close to the forest, surroundings without shelter, different altitudes), their volumes of traffic and their general characteristics (longitudinal and transverse inclinations, road surface characteristics). Besides, different kinds of de-icing agents have been employed (FS 30 as well as brine) and every measurement included a determination of the remaining salt. The SOBO 20 accomplished this task. Road closures were unnecessary for the recording part. Permanently wet surfaces generate the greatest decline in the concentration of de-icing salt on rural roads. Moreover, intense longitudinal and transverse inclinations as well as road surfaces with low profile (when using brine) accelerate the reduction of de-icing agents on road surfaces. Whenever one spreads brine on wet surfaces, the degeneration of de-icing salt reaches its maximum. Therefore, it is not advisable to implement these kinds of actions in winter service routine. Generally, the persistence of de-icing salt on humid road surfaces equals three to four times the persistence of de-icing salt on wet road surfaces provided that the dispersion of the de-icing agent has been performed under equal conditions (when using FS 30). The current investigation is able to provide evidence for an efficient gritting process of de-icing salt. Namely, it identifies the number of passing vehicles, which can overtake a given road section, before it becomes necessary to renew the concentration of the de-icing salt. These insights might be helpful to optimize the winter service sector. As an example, one can say that it is suitable to grit road sections with low volumes of traffic in the evening in order to save time for roads with higher traffic volume. These sections can be taken care of during the morning and shortly before road surfaces become slippery. (Author/publisher)
Abstract