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 54 countries and totals more than 20,000 km of urban rail built since the late 1960s. We have also examined this question in greater detail by carrying out five in-depth case studies that take a closer look at unique considerations and variables that aren’t easily quantified, like project management, governance, site conditions and design.