EVALUATION OF SHOULDERS FUNCTIONS ON LITHUANIAN REGIONAL ROADS

Granular shoulder is an important element of road system. One can frequently notice shoulders rutting, edge breakage, unconformity of cross-section to the norms that could be caused by wind and water-generated erosion. These problems directly affect the drivers, influences their behaviour on the road and traffic safety. Therefore, a constant maintenance of road shoulders is necessary. Investigations of the Lithuanian gravel road network showed that the low-volume roads with gravel surfacing do not correspond to the current standards and the change in their performance due to climatic conditions, traffic volume and the materials used for the structures have a large influence not only on traffic safety but also on traffic conditions. It is very important for the road shoulders to improve traffic safety to prevent road carriageway edges from degradation, to serve for emergency parking and for the installation of guardrails, warning and informatory signs. Since shoulder deformations are caused by the deformations in the subgrade and its slopes, a properly prepared and erected subgrade should be provided with the shoulder of corresponding structure where inadmissible deformations would not occur. Defects in the low-volume road pavement occur when gravel of unsuitable composition is used for the shoulder pavement, the structure is of insufficient thickness and strength, the top of the subgrade becomes damp due to the lack of proper drainage or road maintenance is of unsatisfactory level. It is very important for the shoulders of low-volume roads to use a proper material for increasing the structural strength of the shoulder and preventing it from defects.