Traffic conjestion in the Chinese capital of Beijing is expected to be alleviated to some extent as another subway line opens in a few months.

The north-to-south Subway Line Four is due to open in September while its Majiabu section is now undergoing tests.

The new train runs along an 800-meter test track, testing brakes, deceleration, stopping and signals.

Zhang Yanying is an official with the Beijing Mass Transit Railway Construction Administration Corperation.

"Next we will test the interior fittings, which will be processed between June 20th to September 28th."

Most of the construction is being carried out by Hong Kong's railway operator, Mass Transit Railway Corporation, which will also run the line for 30 years.

The 28-kilometer line is scheduled to open for service at the end of September.

The line will pass through Zhongguancun, Beijing's high-tech center, the National Library of China and the Beijing South Railway Station.

13 subway lines are now being built in Beijing at a cost of more than 50 billion yuan, nearly 7 billion U.S. dollars. That will bring the total number of lines in the city to 19 by the end of 2015.