ROAD ALIGNMENT AND OVERTAKING SIGHT

Design guidelines on alignment standard has been investigated to clarify how trafficability is influenced by sight conditions. The material that has been produced is of two types. One is a study of overtaking behaviour on different types of road (a 13 m road with conventional road markings and a 9 m road), and the other is an analysis of different sight designs. In the empirical study, road users' choice of sight distance for different types of overtaking on the two road types was surveyed. The sight design analysis consists of a large series of traffic simulations in different traffic flows. The effects on trafficability, resulting from different sight designs on 9 m and 13 m roads, have been studied. To evaluate the results, a number of criteria have been proposed for defining efficient traffic dispersion. On the basis of the traffic simulations and the results of the empirical study of overtaking, a number of general design guidelines for 9 m and 13 m roads have been proposed. (A)