The steel rails of steel wheeled trains are generally placed on elevated, reinforced concrete structures when no other alignment can be implemented. When the intensity or sensitivity of existing urban development precludes at grade rail systems, planners and designers may feel forced to simply elevate the same systems and technology above the otherwise unbuildable path they have chosen. Rather than finding alternative routes or entirely different modes of transportation to meet specific transportation objectives or demands, planners and transportation authorities seeking a path of least resistance often resort to creating massive structures in order to implement their projects.
Beyond the dramatic multiplying of construction costs associated with elevating steel rail train tracks, the visual and physical impacts of such adaptation often create blots on their surroundings so negative that they can dramatically degrade the neighborhoods and environments through which they pass. Representing an antiquated and marginally functional mode of mass transportation, construction of new elevated rail systems is virtually impossible to justify when compared against monorail technology, or the choice of alternative routes not requiring elevated infrastructure.