A geology and geomorphology–based decision matrix methodology for route determination of new roads

Selection of the most appropriate route for new roads is of great importance not only from road planning or construction cost points of view, but also from the aspect of geology and geomorphology. In the present study, a novel geology and geomorphology–based decision method for route selection is introduced as an alternative to the classical approach that considers only the minimum cost. In this context, five different routes are determined and evaluated, which connected the new Istanbul Airport to Fatih Sultan Mehmet Bridge, the second intercontinental bridge of crossing the Bosphorus. For the final decision of the best route, the classical solution that considered only the minimum construction cost for infrastructure is compared with that obtained via the newly introduced Geological and Geomorphological Conformity Matrix (GeoGCoM). With this new approach, the potential cases that can be encountered throughout the design lifetime of the route are considered, and as such, the optimum route that would provide the most economical solution in the long term can be determined. Results verified that the one of the best two alternatives found from the GeoGCoM (with weighing factors of 0.8439 and 0.8437) is also the alternative with the least construction cost, which costs 7% less compared to the nearest option. Although GeoGCoM is not meant to replace the cost comparison of alternatives, it is shown to be an effective novel method to satisfactorily account for the geological/geomorphological aspects of different route alternatives, which may not be revealed by cost estimations. Therefore, GeoGCoM assessment is suggested as a complementary analysis to classical cost estimation.