Flow and delay data obtained at five major/minor t-junctions before and after conversion to offside-priority have been used to provide general criteria for conversion of major/minor systems to mini-roundabouts. Two approaches have been adopted. The first is intended to provide an approximate method of estimating the 24-hour delays before and after conversion and the second criterion defines a 'guideline' flow to be compared with the actual daily flow. This 'guideline' flow is the flow through the mini-roundabout required to generate delays equal to those actually observed with the major/minor system. Conversion is justified if the actual flow is less than the 'guideline'. Although these generalised criteria have some limitations and prompt further research in related areas, they offer guidelines to the question of junction choice. Application details for both procedures are given. (Author/publisher)
Abstract