With hosting duties for the Winter Olympics looming over the city, Beijing has kicked efforts to complete its subway system into high gear, resulting in the highest number of subway lines and the longest mileage of track ever worked on at one time in the city's history.

By year's end, construction is expected to be simultaneously performed on 20 different subway lines, measuring a total distance of 354.8 kilometers.

Most of the construction will be extensions added to existing subway lines, but ground will be broken on new subway lines as well.

READ: Beijing Subway Line 12 to Open in 2020, Promises Transfers of Under 100 Meters

A plan, currently under proposal and expected to begin work before 2018, is the new subway line that will serve the Central Business District (CBD). Serving just eight stations and running a total length of 6.5 kilometers, the crooked route will begin at Line 7 to the southeast, run northwest under Beijing East Railway Station and CBD before terminating at Dongdaqiao Station on Line 6.

Even though the new Beijing Airport to the south is not expected to open until 2019, the Beijing Metro is planning to allow commuters to get there through a variety of routes.

In addition to an express light transit connection departing from Beijing West Railway Station, subway commuters will be able to reach the Beijing Daxing International Airport on the future Line 19. Though this year will only see phase 1 of its construction, Line 19 is planned to depart from Mudanyuan Station on Line 10 to the north and wind its way southward past Jishuitan Station on Line 2 and Ping'anli Station on Lines 4 and 6 before crossing the ringed Line 10 (again) at Caoqiao Station before ultimately reaching the new airport (and beyond).

What's more, the new Beijing Airport is planned to be a transportation hub that will not just be connected to the subway and express trains, but a high-speed railway stop as well.

READ: New Beijing Airport Construction Well Under Way; Light Transit Planned from West Railway Station

What's more, the airport express serving Beijing Capital International Airport will be extended westward to Line 5, connecting at Beixingqiao Station.

Also looking far-off into the future is Line 7, which will be extended all the way to the future Universal Studios theme park, as will future plans for the Batong Line.

This year has also seen construction begin on the first stage of the mysterious Line 3. The east-west line is expected to make a stop in Sanlitun at the Workers' Stadium Station.

As with the CBD Line, the Yanfang Line is undergoing final confirmation. The new 6.1-kilometer-long subway line, which is designed to be completely driverless, will serve the southwestern suburb of Zhoukoudian with three stations, connecting it with the current Fangshan Line, a subway line with plans to be extended northwards to meet up with Line 16.

READ: Ride the Beijing Metro by Swiping Your Phone ... As Long as It's Not an iPhone

Beijing's underdeveloped west suburban public transportation infrastructure will be bolstered by the Xijiao streetcar line as well as the S1 Line. This new line will extend westward from Pingguoyuan, the terminal station for both Line 1 and Line 6, once it is connected by this year's expansion. At the same time, construction work will extend Line 16 by curving it southward to Xiyuan Station.

Meanwhile, other subway construction projects include phase 3 and 4 of Line 8 that will curve the Olympic Park-serving subway to circumvent the Forbidden City and extend it southward past Lines 2, 7, 14, and ultimately Line 10. Additionally, work will begin on Line 17, a subway line expected to also have a stop in Sanlitun.

The Beijing Metro is currently comprised of 19 subway lines and 345 stations. After this year's massive expansion, it won't be long before Beijing's incredible subway expansion gets the attention it deserves.

Here's how the Beijing Metro is expected to look in 2021 (map already out of date):

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Twitter: @Sinopath

E-mail: charlesliu1@qq.com

Images: Weibo, People