The second phase of Beijing's Subway Line 6, planned for trial operation by the end of 2014, will extend the line to 43 kilometers east-west through the city and boost the public transport system, an official said on Wednesday at a press conference.

Line 6, which also links Line 1, will form a key channel for workers and residents traveling in those directions, said Zhang Wenqiang, director of the rail transport department under the Beijing Municipal Commission of Transport. It will connect the eastern Tongzhou district, the planned sub-center of the city, with the downtown area, and help spur the development of surrounding areas, he said.

The newly constructed section in Tongzhou is 12.4 km long with eight stations. The stations are also designed to reflect the local history and culture.

The Beiguan and Xinhuadajie stations of the section are also designed to transfer commuters to the planned Line R1 and Line S6, which are part of the city's long-term transport blueprint.

Passenger flow on Line 6 is now about 600,000 trips a day, which is expected to rise to 800,000 trips in the initial stages of the operation of the new section. Train intervals will be shortened to three and half minutes during the morning peak hour from the present four minutes, and to three minutes for the evening rush hour.

The length of Beijing's subway network will hit 527 km once the 62 km of line extensions including the latest on Line 6 are rolled out by the end of 2014, said Zhang Chengman, an official of the Beijing Rail Transport company.

By May 2014, Beijing had 17 operating railway lines totaling 467 km (excluding Line S2), with 231 stations. The subway system, covering 11 districts, handles 10 million trips in one workday and about 11.55 million during peak days. Billed as the busiest metro system in China, it also claims three top rankings in terms of operating time, passenger capacity and the number of departures during rush hour.

Plans to build a subway system in Beijing began in 1953. Subway Line 1 started in 1965 and was completed in 1969. It was the first metro in China.

Beijing subway milestones:

- Sept 15, 2004: Beijing Subway website launched.

- Oct 16, 2004: Barrier-free access on Line 1 and Line 2.

- Newly designed air-conditioned trains put into use on Batong Line before May 1, 2005. The old trains used natural ventilation instead of air-conditioning.

- Oct 9, 2005: Mobile TV successfully broadcast on Line 13.

- June 9, 2008: Auto-ticket system launched, ending 38 years of using paper tickets.

- June 29, 2008: Security checks carried out in runup to Beijing Olympics and continue from then on.

- Aug 8, 2008: Round-the-clock service (excluding Airport Express) on first day of Beijing Olympics. The departure of the first train on the Olympic Branch Line at 4:38 am symbolized the 45-hour non-stop operation of the system for the first time, breaking the record for longest operating time since its introduction in 1969.

- Sept 28, 2009: Opening of Line 4, the second north-to-south artery after Line 5.

- March 8, 2013: Record set for transporting 11.05 million people on a single day, ranking first in usage rate worldwide for the first time.

- Nov 13, 2013: Beijing Municipal Commission of Transport announces installation of screen doors in all stations on Line 13 and the Batong Line before the end of 2013.

- May 22, 2014: The 11th session of the 14th Standing Committee of the Beijing Municipal People's Congress discusses safety rules for the subway, including the Urban Construction and Environmental Protection Commission's suggestion to add three rules to prohibit eating, begging and the distributing of advertisements.

- The first batch of "unmanned" trains will be unveiled on the Yanfang Line by the end of next year. The trains are expected to run automatically with a set of actions to stop or depart without the intervention of drivers or crew members.