Some of the busiest lines on the London Underground will be partly closed every weekend for seven years when the government's part-privatization of the network comes into effect, reported The Daily Telegraph. Metronet, the company that will take over the infrastructure of eight of the 11 lines, is planning a radical track replacement program. Much of the existing track is at least 25 years old, and some conductor rails have not been changed since the 1920s, said the paper.