ON FINDING REALISTIC TURNING FLOWS AT ROAD JUNCTIONS

The authors explain that the economic assessment of many inter-urban road schemes is carried out by means of the department of transport's cost-benefit analysis system coba, published by H.M. Stationery office in 1973 as - a method of economic appraisal of highway schemes. In preparing data for this system, users are often faced with the need to specify turning flows of traffic at junctions when the only data they have is that of link flows. This problem is discussed in this paper, and an outline is given of the mathematical theory behind the methods employed. The terms used are defined and discussed, and as a result the explanation of the methods employed is simplified. The basic concepts are defined, and a description given of symmetrical flow patterns, i.e. junctions where, over the time period considered, the flow into the junction along each link is the same as the flow out of the junction along the link. A number of illustrative examples are given designed to illustrate how turning flows can be determined. /TRRL/