Transit Costs Project

The Transit Costs Project (discovered by Pedestrian Observations) aims to collect cost details of transit infrastructure projects around the world from researchers at NYU Marron Institute of Urban Management. In their own words:

Why do transit-infrastructure projects in New York cost 20 times more on a per kilometer basis than in Seoul? We investigate this question across hundreds of transit projects from around the world. We have created a database that spans more than 50 countries and totals more than 11,000 km of urban rail built since the late 1990s... The goal of this work is to figure out how to deliver more high-capacity transit projects for a fraction of the cost in countries like the United States. Additionally, we hope that our site will be a useful resource for elected officials, planners, researchers, journalists, advocates, and others interested in contextualizing transit-infrastructure costs and fighting for better projects.

There are some visualizations and case studies released based on the data.