Studying Roundabout Performances Using Kriging Techniques

Generally road intersections are the most dangerous places into the road space. This is mainly caused from the many conflicting points existing in that road area. Generally roundabout reduces considerably the number of conflicting points with respect to a stop or yield intersection, from 32 to 8 conflicting points. For this reason, in recent years, many countries have adopted roundabouts as a design solution for both urban and rural road intersections. This happens even if the available space is not enough: for this reason, there are a lot of non-standard roundabouts, for example with one of legs without deflection. The absence of deflection can modify the roundabouts performance. Roundabout works well if specific traffic and geometric conditions exist. The parameter used to estimate if a roundabout can work well or not is its capacity (where capacity is defined as the maximum entering flow). One of more popular method to investigate roundabout performances is based on the relationship between entering flow (Qe) and circulating flow (Qc). These models have been built by using statistical regressions and only for well designed roundabouts. The paper reports a different approach to the phenomenon: an approach based on geostatistical theories, which consider the relationship between Qe and Qc as a regionalized phenomenon. According to this collected data are not random values but are supposed to be related to each other with a defined law. The paper analyzed both roundabouts with and without deflection.