The third primary route is the Trans-Mongolian Railway, which coincides with the Trans-Siberian as far as Ulan-Ude on Lake Baikal's eastern shore. From Ulan-Ude the Trans-Mongolian heads south to Ulaan-Baatar before making its way southeast to Beijing. In 1991, a fourth route running further to the north was finally completed, after more than five decades of sporadic work. Known as the Baikal Amur Mainline (BAM), this recent extension departs from the Trans-Siberian line at Taishet several hundred miles west of Lake Baikal and passes the lake at its northernmost extremity. It crosses the Amur River at Komsomolsk-na-Amure (north of Khabarovsk), and reaches the Tatar Strait at Sovetskaya Gavan.