China’s expanding metro system has hit a new milestone, with about 4,600 kilometers built since the country’s first subway line opened in Beijing in 1969,  the 21st Century Business Herald reported.

Unsurprisingly, Shanghai led the way with an operating mileage of 669 kilometers as of June, followed by Beijing and Guangzhou, with 617 kilometers and 473 kilometers respectively, the newspaper said. As a whole, 13 out of the 33 cities ran lines exceeding 100 kilometers in the same period.

However, the financial situation in operating these urban rail networks was not satisfactory, according to the 21st Century Business Herald.

While over 600 billion yuan (US$86.69 billion) was invested into the sector, only a few cities managed to break even financially.

Data from 28 cities showed that the ratio of revenue and expenditure stood at 78 percent in 2018 after increasing 8 percentage points from the previous year. Only four cities — Hangzhou, Qingdao, Shenzhen and Beijing — achieved balance last year.

In the meantime, six out of 29 cities, including Kunming, Ningbo, Xiamen and Guiyang, recorded less than 7,000 visits per kilometer for each day, below the 7,000-visit bottom line required by the National Development and Reform Commission.