San Juan is the capital of Puerto Rico and has 1.1 million inhabitants.

First line of the Tren Urbano under construction since 1997. Initially planned to open in 2001 it suffered some delays After trial service began in Dec. 2004, regular revenue service started eventually on 6 June 2005.

Initially planned with a length of 17.2 km and 16 stations, mainly elevated or at grade, underground at Río Pedras (Río Pedras and Universidad stations) and in downtown San Juan, the district of Santurce (San Mateo and Minillas stations). The latter section was postponed for an indefinite future.

The first trains produced by Siemens in Sacramento (California) arrived in March 2000.