Subway Line 4 goes into operation in Shenzhen, Guangdong province, June 16, 2011. [Photo/Xinhua] The 20.5-km subway line starts at Qinghu Station in north Shenzhen to Futian Port Station in the south.

The project, reportedly the first of its kind in the world, will see robots ride subway trains to deliver goods to more than 100 stores across Shenzhen.