BEIJING, Dec. 28 -- Beijing began trial operations of four new subway lines on Sunday in the latest effort to ease the city's traffic jams.

The new lines have increased the total subway length of Beijing to 527 kilometers, increased by 13.3 percent year on year.

The newly-opened lines include the second phase of No. 6 Line, the No. 7 Line, the eastern section of No. 14 Line, and the western section of the current No. 15 Line.

The new lines are more passenger friendly, said Xu Chengyong, who is in charge of Beijing subway construction with the Beijing Urban Construction Design & Development Group.

Xu said the new lines will provide more convenient transfer channels and spacious carriage for passengers.

No. 14 Line is the first metro line in the capital to use high capacity wide-body A size trains, while No. 6 Line uses high capacity rolling stock to date featuring eight-car size train sets.

The city's subway system carries approximately 10 million passengers daily on workdays. By 2015, the number of subway lines in Beijing will reach 19. By 2020, the total subway length is expected to have increased to 1,000 km.