Yangchenghu Tunnel had been put through a preliminary test and is expected to go into use soon. It marks the completion of Middle Ring Expressway in Suzhou, according to the local traffic department.

The six-lane tunnel, with the length of 2.31 kilometers and average width of 48 meters was built on the basis of the standard of first-class highway. Its maximum design speed reaches 100 km/h.

"Supply lines in the tunnel work now as lights, electronic signs and monitoring have been installed," said a staff of the construction team.

It will be a 20-minute drive between downtown Suzhou and the boundary between Suzhou and Wuxi.