Beijing subway's Changping Line was put into trial operation Sunday and is scheduled to go into official operation by the end of 2010, said subway constructors.

The Changping line, together with four other lines scheduled for operation by the end of the year, will extend the length of Beijing's subway to 300 km, according to subway constructors.

The line links Xi'erqi station on Line 13 to Chengnan Station in Changping District, with seven stations covering 22 km. The designed train speed is 100 km per hour, said a spokesman with Beijing Railway Construction and Management Co., Ltd.

The second phase construction will extend the line to the city's far north, Thirteen Tombs Scenic Area, covering 10 km with five stations, he said.

Four new lines, namely Yizhuang Line, Fangshan Line, Daxing Line and No. 15 Line, will open in 2010. Beijing plans to extend subway system to 561 km by 2015.