the effect of candidate routes alignment over transit coverage in a grid network

The design of public transportation (transit) route networks involves identifying the most efficient configuration of routes in an urban setting so as to maximize an objective function, such as network coverage, within the available budget. this problem is generally addressed through two key stages: the generation of potential candidate routes to be selected and the subsequent selection of final routes. according to the literature, the pool of candidate routes in the first stage plays a critical role in determining the quality of the selected routes in the second stage. however, in certain network topologies, such as grid-structured networks, urban planners often prefer introducing candidate routes oriented horizontally (east-west) or vertically (south-north). the impact of restricting the candidate routes to exclusively horizontal and vertical routes has not been studied much in existing research. to address this gap, this study examines two scenarios: (1) unrestricted candidate routes and (2) candidate routes restricted to horizontal and vertical orientations. the results averaged for a 6×10 grid network suggest that adopting horizontally and vertically restricted candidate routes results in only a 2% reduction in network coverage compared to using unrestricted candidate routes.