\r\nAccording to Mr Peter Walker, president of S\u00e3o Paulo Metro, works should start by mid-August. The Reais 8bn ($US 3.9bn) line will be the city's second PPP metro project after Line 4, which opened in 2010.\r\nThe north-south Line 6 will be 13.5km long with 15 stations and will link Brasil\u00e2ndia with S\u00e3o Joaquim on Line 1. It is considered one of the most difficult metro lines to build because of the need to tunnel beneath the Tiet\u00ea River at a depth of more than 60m.\r\nThe line will serve university campuses and the district of Higienopolis and is expected to carry around 640,000 passengers per day. It is due to be commissioned in 2019.\r\nS\u00e3o Paulo Metro has also announced it will begin test operation with CBTC on Line 2 on January 13. Trains will operate without passengers on the section between Alto do Ipiranga and Ana Rosa.