Until recently no satisfying method was available in the Netherlands to weigh one junction type against another, such as to choose between a signalized intersection and a roundabout. To remedy this situation the Dutch consultant Goudappel Coffeng has started a project to develop software (Junction Explorer) to do this in a consistent way. The purpose of this decision support system is to estimate values for capacity, delay, emissions, safety and required space for different junction types. The function of the Junction Explorer is to help decision-makers and designers in their task. This paper deals with the development and calibration of a method to determine the capacity and the resulting delay of single-lane and two-lane roundabouts. The model developed is suitable for both types of roundabouts but could so far only be calibrated for the single-lane type, due to a lack of sufficiently saturated cases of two-lane types. The paper is therefore limited to single-lane roundabouts. In 1998 new Dutch design recommendations for roundabouts were published (CROW, 1998). These recommendations include right-of-way for cyclists on roundabouts in built-up areas. The influence of cyclists on capacity cannot be neglected in The Netherlands; therefore the model presented in this paper explicitly takes into account the influence of cyclists. The operational aspects of the recommendations from CROW were based on this model. (A)
Abstract