Graph-theoretic evaluation support tool for fixed-route transport development in metropolitan areas

This paper presents a graph-theoretic analysis for supporting the evaluation of alternative fixed-route public transport development plans in metropolitan areas. Several indicators grounded on the theory of graphs and network science are suggested and calculated for evaluating prospective developments of the fixed-route transport system in the Athens metropolitan area, which includes the metro, tram and suburban railway. The comparative static analyses of past and scheduled line extensions and planned line constructions generally show the tendency of the system towards small-world networking with scale-free characteristics, which implies increasing scale economies and reliance on a few large transfer stations. The results suggest that policy-makers can choose the option of constructing a semi-circumferential line in the middle (compared to the end) of the system development process, in order to trade investment cost for increased levels of service and robustness.