Line 4 of the Santiago Chile LRT was successfully inaugurated on 30th November 2005, in the presence of the Chilean President, Ricardo Lagos, the Minister of Public works, Rodrigo Estévez, and other officials.

The Managing Director of SYSTRA, Philippe Citroën, and Alain Caire, Director of Safety for RATP, were also present at the ceremony, alongside the Chairman of METRO S.A., Fernando Bustamante and the Managing Director, Rodrigo Azócar.

SYSTRA, in association with its long-standing Chilean partner, Cade IDEPE, has in fact been involved in every phase of this project since studies began in 2002 :

• preliminary and detailed design ;
• structural design of the U viaduct, supervising work on the construction of the pre-fabricated arches, assembled on-site ;
• construction of 7.7 km of viaduct in nine months, with three cantilever beams ;
• review of studies, in particular for the Automatic Train Control system (Urbalis 200) ;
• specialist assistance with construction and commissioning (a specialist team of engineers was assigned full-time on-site) ; and
• inspection of rolling stock manufactured in Brazil.

The construction of line 4 is part of a medium-term transport plan (PTUS, Santiago Urban Transport Development Plan) defined by the government and the city authorities at the start of the decade, which provides for a complete reorganisation of surface transport, based around improvements to the metro system. As a result, in 2002, METRO S.A. embarked on an ambitious construction policy.

The aim was to double the length of the network by 2005, adding around 40 km of line. This resulted in the creation of a new line, line 4 and 4A, and the extension of existing lines 2 and 5, to provide a fully-integrated network.

Line 4 (24 km) and 4A (8 km), runs on wide-gauge rails with a 750-volt power supply provided by a 3rd rail. The track is laid on concrete slabs and runs partially on viaduct (7.7 km) at ground level and in tunnels. The total length of line 4 and 4A is 32 km.

The expected volume of traffic for line 4 alone is 325, 000 passengers a day.