Paper by BLAB STEIGENBERGER from ISCR 10th 2006 Brussels Belgium
Design and construction of road intersections in the form of roundabouts is getting more and more popular not only in urban areas but also on highly trafficked primary rural roads due to their high road safety potential. Well designed roundabouts show improved safety characteristics by reducing the number and, particularly, the severity of collisions. Whereas a number of excellent guidelines exist for the geometric design of roundabouts for a variety of traffic volumes and terrains, only little information is available as regards appropriate pavement design and constructional details of such road areas. Road pavement surfaces in roundabouts are exposed to particularly high levels of stresses owing to the impact of horizontal shear forces resulting from the braking and accelerating action of entering and exiting vehicles as well as the centrifugal forces of pass-through traffic. As a consequence, flexible pavement constructions in roundabouts frequently develop heavy rutting due to the visco-elastic material behaviour of hot mix asphalt. Therefore, concrete pavements in roundabouts are increasingly becoming an attractive alternative option for road operators due to their significantly lower maintenance costs and longer service lives. However, these benefits of concrete pavements in roundabouts can only be realized with proper design of slab geometry, concrete mixes, and dowel and joint layout, and careful construction work performed by skilled personnel. The paper presents the state of the art in concrete pavement design and the construction of roundabouts in Austria and the lessons learned from past experiences. The collected expertise and construction recommendations will be incorporated in an Austrian design guide for roundabouts with concrete pavements.