"It’s not just the Second Avenue Subway"

Over at Citylab, Alon Levy has a great piece on the costs of passenger rail.

The approximate range of underground rail construction costs in continental Europe and Japan is between $100 million per mile, at the lowest end, and $1 billion at the highest. Most subway lines cluster in the range of $200 million to $500 million per mile; in Amsterdam, a six-mile subway line cost 3.1 billion Euros, or about $4 billion, after severe cost overruns, delays, and damage to nearby buildings. The Second Avenue Subway is unique even in the U.S. for its exceptionally high cost, but elsewhere, the picture is grim by European standards:

Line	Type	Cost	Length	Cost/mile
San Francisco Central Subway	Underground	$1.57 billion	1.7 miles	$920 million
Los Angeles Regional Connector	Underground	$1.75 billion	1.9 miles	$920 million
Los Angeles Purple Line Phases 1-2	Underground	$5.2 billion	6.5 miles	$800 million
BART to San Jose (proposed)	83% Underground	$4.7 billion	6 miles	$780 million
Seattle U-Link	Underground	$1.8 billion	3 miles	$600 million
Honolulu Area Rapid Transit	Elevated	$10 billion	20 miles	$500 million
Boston Green Line Extension	Trench	$2.3 billion	4.7 miles	$490 million
Washington Metro Silver Line Phase 2	Freeway median	$2.8 billion	11.5 miles	$240 million
Atlanta I-20 East Heavy Rail	Freeway median	$3.2 billion	19.2 miles	$170 million

It is hard to find exact international comparisons for subway lines running in the medians of freeways. However, it should not be much more difficult to construct such lines than to build light rail. Indeed, in the study for Atlanta’s I-20 East extension, there are options for light rail and bus rapid transit, and the light rail option is only slightly cheaper than the heavy rail option, at $140 million per mile.

Lists of light-rail lines built in France in recent years can be found on French Wikipedia and Yonah Freemark’s The Transport Politic, and in articles in French media. The cheaper lines cost about $40 million per mile, the more expensive ones about $100 million.
In the United States, most recent and in-progress light-rail lines cost more than $100 million per mile. Two light-rail extensions in Minneapolis, the Blue Line Extension and the Southwest LRT, cost $120 million and $130 million per mile, respectively. Dallas’ Orange Line light rail, 14 miles long, cost somewhere between $1.3 billion and $1.8 billion. Portland’s Orange Line cost about $200 million per mile. Houston’s Green and Purple Lines together cost $1.3 billion for about 10 miles of light rail.