In April1991, the first line of a mass transit rail system (Metro) for Monterrey, Nuevo Leon, Mexico, was brought into service. The 18.7 km (11.6 mile) line is an elevated bridge structure stretching over existing streets, consisting of segmental precast concrete spans that val}' in length up to a maximum of 47 m (154 ft). There are 17 elevated stations on the line, combining precast and cast-in-place concrete in the column beam-slab structures and in the adjacent platforms. More than 6500 precast concrete bridge segments and 2700 other elements were cast in a specially designed, state-of-the-art plant located north of the city. Segments were match-cast on concrete beds long enough for each complete span, then delivered by trucks to the site, erected span-by-span on movable steel trusses and post-tensioned. The precast concrete box girder segments have pretensioned top slabs, 7.40 m (24 ft 3 in.) wide, that support two parallel, standard gauge tracks. The electrified metro trains have up to four cars and operate at a design speed of 70 km/hr (43 miles/hr). The line was built by a consortium of three Monterrey contractors in just under 40 months from start of design to its opening.
