The line is 12.5km long and runs from the city centre to Juan Manuel de Rosas with 17 stations, and carries around 250,000 passengers per day.

Line B is electrified at 600V dc third rail and the 15-month project involves installation of new medium-voltage ring cables, third rail power supply and tunnel disconnections, as well as modifications to substations.

Alstom resignalled the line in 2013, and this latest project is designed to increase capacity.