In many cases, and both in terms of traffic safety and traffic flow, the system of mini roundabouts in intraurban road networks has proven itself. Whereas in practice, a quite uneven arrangement or design of key elements such as circular islands, road dividers and pedestrian crossings, is considered as being problematic. Moreover, and because of advantages in terms of land use and costs especially on major roads and in local traffic, important application criteria such as recognizability and capacity constraints are considered less important. The aim of the research project was therefore to collect in practice encountered diversities, and, on the basis of empirical studies, to win reliable conclusions on road safety and quality of traffic flow, depending on the position and function within the traffic network and on the respective configuration of the mini roundabouts. The methodological approach and the resultant work program for the implementation include five incremental, partly parallel steps: - overview and classification of existing mini roundabouts by means of a nationwide research using questionnaires, - evaluation of traffic safety in approximately 100 mini roundabouts (analysis of accident characteristics, structure of accidents and of casualties) and calculation and comparison of accident characteristics, - evaluation of the traffic quality and development of a calculation method based on 10 case studies, - survey of noise pollution at mini roundabouts with different surfacing of the traffic island, and - derivation of recommendations. As a result, basic accident cost rates for mini roundabouts to be included in the HVS handbook were proposed. For the assessment of traffic flow, a method proposal for the HBS handbook was derived, based on the time gap theory. Also, the effects of different types of roundabouts on noise nuisance were calculated, and recommendations on application areas and application limitations of mini traffic roundabouts were derived. (Author/publisher)
Abstract