This thesis elucidates the various intricacies and elements behind the selection process and gives the industry’s view of the many aspects of the elements involved e.g. cost, safety etc. The results were obtained via questionnaires and a number of interviews. The thesis provides brief cost comparisons and background to various tunnels around the world. The whole chapter is devoted to the evaluation of the benefits in terms of passenger safety, station layout and environmental impact. As no two construction projects are identical, various conclusions might differ from project to project. Two projects which have been selected are Dublin Metro North and DART Underground which were both planned for the Dublin area. Conclusion chapter summarise findings, objectives and hypothesis of this thesis.