A GUIDE TO THE ECONOMIC JUSTIFICATION OF RURAL GRADE SEPARATIONS

The paper presents the results of a simple analysis to determine the economic justification of interchanges and overpasses for rural expressways. The economic worth of grade separation is calculated using an elementary simulation model to determine road user savings which are calculated for reductions in accidents, fuel consumption and delay. The cross road volumes necessary to justify grade separations for the range of traffic flows on the expressway are set out. The results indicate that previously used guides have resulted in grade separations being constructed before they were justified on economic considerations. The results of the analysis can be used to ascertain whether grade separations should be constructed in conjunction with the duplication of the major road or whether such works should be deferred. Language: en