The Jubilee line is a London Underground line. Opened in 1979, it is the newest line on the network (though some sections of track date back to 1932 and some stations to 1879). At its northern end, it took over what was previously the Stanmore branch of the Bakerloo line, while the new build was completed in two major sections: initially in 1979 to Charing Cross tube station in central London; then extended in 1999 with the Jubilee Line Extension to Stratford station in east London. The later stations are larger and have special safety features, both aspects being attempts to future-proof the line. Following the extension into East London, serving areas once poorly connected to the Underground, the line has seen a huge growth in passenger numbers and is currently the third busiest on the network, with over 213 million passengers per year. Thirteen of the 27 stations served are below ground.