Towards An Optimum Solution for Underground Rapid Transit

Criteria are developed and evaluated for the optimization of the benefit to cost ratio for the underground portion of a fixed-rail rapid transit system. Such criteria include the evaluation of the broad concepts of cost, functional design and aesthetic design. Cost comparisons identify such major items of work as the relocation of utilities, the underpinning of adjacent structures, the construction of the temporary retaining structure together with the excavation within its confines, the construction of the finished structures that house the system and the duration of the period of construction. Functional comparisons are evaluated on the basis of accessibility to trains, flexibility for future expansion and ease both of policing and of janitorial maintenance. Aesthetics are evaluated on the basis of open space, passenger comfort and lighting. An actual case history is investigated to develop an optimum solution.