Evaluation of roundabout entries reliability

This paper presents criteria to evaluate roundabout performance reliability. After introducing and justifying the adoption of reserve of capacity and rate of capacity as performance functions, the discussion is developed using a general calculation criterion in which the values that are involved in the limit state service condition – traffic demand and entry capacity – are random variables described by their probability density functions, that is to say by their distribution functions. A lower level criteria is then identified with which, on the basis of the estimation of suitable statistics of the performance function, a reliability index is calculated that can be compared to a prefixed reference value. Using a set of numerical applications performed on the basis of the adoption of some of the methods for capacity calculation that are more largely used in the technical practice, the criteria elaborated are concretely exemplified.