Vehicles are one of the main causes of air pollution in Beijing, and with around 1,000 new cars hitting the capital's roads each day, the government has introduced various measures to ease congestion and lower pollution levels before the start of the Summer Olympics on August 8.
Xinhua news agency said the new subway lines, built at a cost of 22.3 bln yuan ($3.2 bln dollars) will increase the system's total track length by around 40% to 200 km (124 miles).
As of Monday morning, Beijing will start a traffic reduction scheme under which cars with even and odd number plates will be permitted to drive on alternate days. The two-month scheme, which has already undergone trials, is expected to take one million cars off the roads and force around four million extra people to use public transport, according to Xinhua.
Zhou Zhengyu, deputy head of Beijing's Municipal Committee of Communications, said on Thursday that the trains used for the new lines will have a capacity of 1,424 passengers each, 344 more than on older lines.
The opening of the lines, linking to the new international airport and Olympic facilities, had originally been scheduled for June. The city plans to build another seven subway lines by 2015.
As part of pollution reduction measures, Beijing is also increasing its bus fleet to cut car use, and suspending operations of cement and petrochemical plants until September.