Recent developments in junction design.

The department of transport has issued completely revised advice on junction design in the past two years. This advice has many differences to the past approach. Some of the new features are based on research and some on existing good practice. Extensive speed/flow research led to the reduction in recommended sizes of major/minor junctions, and thousands of site observations went into the production of the Arcady, Picady and Midas capacity programs. Accident studies completely vindicated the department's stand on entry deflection at roundabouts, but were not conclusive on approach gradients or visibility. Perhaps further studies are required on the latter two. Innovations by enterprising engineers that have worked well in the field have been taken up and actively promulgated. For instance, at roundabouts, these include segregated left turning lanes, new methods of approach lane markings and the radical ring junctions. Advice on roundabout crossfall design is essentially a distillation of existing good practice. The provision of adequate turning space for HGC's at roundabouts and major/minor junctions is now covered by the track program. The above and many other minor advances will be discussed in the paper. However, it cannot be pretended that the task is finished, and the paper will also raise some questions on the need for further improvements.(a) this paper is presented in an abstract form. For the covering abstract of the proceedings see IRRD 274491.