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Highlights An improved distance transform for railway alignment in mountains is proposed. Constraints on geometry, structures and location are handled. A dynamic adaptive neighborhood mask is developed. A bi-directional search strategy is proposed to generate various alternatives. Promising alternatives satisfying multiple constraints in mountains can be found.
Abstract Railway alignment design is complex and time-consuming, especially for mountainous areas where the natural terrain gradient between the start and end points greatly exceeds the maximum allowed design gradient. Existing methodologies can optimize routes in areas with relatively simple topography, but often fail in finding the feasible alternatives in complex mountainous terrain. Thus, a two-phase methodology is proposed for optimizing multi-constrained 3-dimensional railway alignments. We generate various promising paths in the first phase and refine them into final alignments by fitting the required curved sections in the next phase. Firstly, the study area is represented using a 3-dimensional rectangular lattice and a comprehensive geographic information model is specified to store and manage the geographic information in this lattice. Secondly, an objective function is developed for estimating the railway alignment’s comprehensive cost. Thirdly, a multi-constrained distance transform is employed as a new approach for generating optimizing paths through various cells in the lattice. Multiple constraints on geometry, structures and locations are handled in this approach. To avoid possible failures in finding paths in the complex mountain regions due to multiple constraints, an adaptive neighboring mask and a bidirectional scanning strategy are proposed for generating various promising 3-dimensional paths. In the alignment fitting process we form the initial alignment by recursively inserting points of intersection and then optimize the final alignment using the mesh adaptive direct search algorithm. The effectiveness of the approach is verified through a real-world case study in a mountainous area where the natural terrain gradient is nearly triple the maximum allowed design gradient. The results show that this methodology can automatically find various promising alternatives, while satisfying the complex constraints.
Methodology for optimizing constrained 3-dimensional railway alignments in mountainous terrain
Tramsportation Research, Part C: Emerging Technologies ; 68 ; 549-565
2016-05-17
17 pages
Article (Journal)
Electronic Resource
English
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