Before the surface electric urban railway (the technology of former streetcar and interurban systems) was reborn as light rail transit (LRT) in the mid-1970s, North American urban areas that wanted urban rail for their inner cities really didn’t think there was any choice other than a full subway-elevated system — rail rapid transit, aka a metro system.
But not only was the expense of such a system daunting, and way above the financial capability of most moderate-sized and smaller American cities, its tremendous capacity generally wasn’t needed for cities just trying to get their feet wet with better-quality public transit.
Then, LRT as an option began to emerge, unveiled with maximum force at the first National Light Rail Conference of the Transportation Research Board (TRB) in 1975, and … ka-boom! Urban rail systems in the form of lower-cost LRT began to sprout up in city after city. And they’ve been widely hailed as a great success and model for good urban public transport.
But the “why not a subway?” issue keeps rearing its head — mainly reflecting the resistance of the motor-vehicle-focused mindset to having urban space, especially street space, shared or usurped by mass transit operations. Overwhelmingly, surface LRT in one type of alignment or another (from street reservations to the re-use of abandoned railway corridors) has triumphed … although there have been cases where pressure to “build it out of sight” has forced new LRT startups underground (or even canceled planned projects altogether).
The tremendous investment cost of digging a subway and installing underground stations is obviously a huge deterrent to the development of such systems — both in the initial financing, and in sopping up available resources that could otherwise be plowed into vigorous expansion of the system. Buffalo’s 6.4-mile LRT line, for example, was constructed almost entirely (81%) in subway … and hasn’t been expanded one foot since its original opening in 1985.
One should keep in mind that the cost of more modest local projects (such as wastewater tunnels or similar smaller tunnels) can be very deceptive. Rail transit subways involve far more complex features (after all, they must provide environments to enable large numbers of human beings to survive underground safely and comfortably). There must be ventilation and lighting, of course, and often air-conditioning. More significantly from a cost standpoint, underground stations are extremely expensive, including access (elevators and escalators designed to convey large volumes of passengers rapidly up and down). Access for trains to get from the surface into the subway can also be expensive, typically involving portals spanning up to two city blocks and lengthy underground approach ramps to and from the level main subway alignment.
Nevertheless, from one city to another, subway enthusiasts (or, often, anti-rail Road Warriors seeking to tie a subway albatross around the neck of local rail planning) continue to emerge from time to time claiming that subway construction would cost only “slightly more” (or sometimes, even, “no more”) than installing a new urban rail line in public streets.
So a solid fact check is in order. After considerable investigation, the study summarized here has gathered a selected assortment of recent urban rail projects (all from the 2000s), either completed or well under construction and fully budgeted. A major and very helpful source has been
Comparative Subway Construction Costs, Revised from the
Pedestrian Observations blog, including data cited in comments. Additional data has come from
Tramways & Urban Transit magazine (hardcopy only), September 2013 through February 2014 issues, data in
Light Rail Now,
Wikipedia, and the research study
Comparative examination of New Start light rail transit, light railway, and bus rapid transit services opened from 2000, co-authored by Lyndon Henry and Dave Dobbs, and presented in November 2012 to the 12th National Light Rail Transit Conference in Salt Lake City, sponsored by the TRB and American Public Transportation Association (APTA).
In this cost comparison, only full subway projects (entirely or nearly totally underground) are included. These also include LRT subways (e.g., San Francisco’s Central Subway, and underground LRT projects in Seattle). LRT projects are exclusively (or nearly so) in street alignments (e.g., San Francisco’s T-Line, Salt Lake City’s University line), and involve full-capability, high-performance LRT rather than streetcar technology. In some cases (e.g., Houston, Phoenix, Minneapolis), construction may include short segments on bridges or an exclusive alignment, but most construction is in-street. (LRT development is being aggressively pursued worldwide, and
there are many more LRT projects recently constructed or now under way than are included here — but keep in mind that this study focuses
only on projects with exclusive or nearly exclusive in-street construction (to compare the most difficult, highest-cost type of surface construction with subway construction). For most LRT projects, in-street construction may only represent a portion of the total alignment.)
All projects include costs of vehicles and facilities, as applicable. One should also note that the unit cost of an extension project is typically less than that of a new-start project, since basic storage-maintenance facilities and a vehicle fleet are often already in place, with perhaps only incremental additions required.
Per-mile unit costs (millions of U.S. dollars per route mile) have been calculated from total project costs and project lengths, and escalated to 2014 dollars.
