The Boston Case:

The Story of the Green Line Extension

+ Eric Goldwyn, Alon Levy, Elif Ensari

Why the Green Line Extension

Boston and its GLX project form the first of six cases that we are tackling in order to understand how one can build public transportation more efficiently and less expensively. When choosing cases, we looked for a number of different variables to avoid drawing general conclusions from sui generis examples. These include the following:

- For the first American case, we wanted to avoid New York. The reason is that while American costs are generally high, New York’s are uniquely high, and therefore it is likely New York has an unusual set of failures not seen elsewhere in the country.

- Capital construction costs in Massachusetts have exploded over the last 40 years. While there hasn’t been any expansion of the existing network since the 1980s, we see in Table 1 that even after adjusting for inflation, GLX is only 6% cheaper per kilometer than the Red Line extension to Alewife, which is entirely underground and has deep, cavernous stations. The Orange Line project may be a better comparison because the majority of the project was at-grade, with a short tunnel under the Charles; GLX, without any tunneling, is more than twice as expensive per kilometer.

- We need excellent quantitative data in order to be able to see if there is a specific thing that went wrong. There is fairly uniform data reporting throughout the United States, but certain public-private partnerships like that of the Maryland Purple Line make it hard to disaggregate data.

- We need excellent qualitative data, that is access to many different experts and practitioners who could help us understand what is going on. For idiosyncratic reasons, we have better access to such sources in Boston than in the rest of the United States save New York and California.

- The history of GLX is dramatic: as we explain in more detail below, planning activities for GLX began in 2004 and continued through 2012. It underwent a cost explosion, and, in 2015, it was threatened with cancellation before it was rebooted with a new design, budget, and project delivery, leaving nearly $700 million of the old project’s budget as a sunk cost. Each of these periods in GLX’s story provide an opportunity to assess why costs diverged from expectations and how the MBTA salvaged GLX. Lessons learned here, will provide avenues of inquiry as we pursue future cases.


Read the Case Study

Eric Goldywn is a Research Scholar in the Transportation and Land-Use program at the NYU Marron Institute.

Alon Levy is a Fellow with the NYU Marron Institute. Alon's work focuses on public transportation and how to apply best practices from cities around the world.

Elif Ensari is a Research Scholar in the Transportation and Land-Use program at the NYU Marron Institute.

Back to top
see comments ()