Construction workers take a group photo in front of the completed Mide Tunnel on the Jiangeyuan Highway. [Photo provided to chinadaily.com.cn]

After more than three years of work, one lane of the Mide Village Tunnel on the Jiangeyuan Highway in Yunnan province was completed on Sunday, marking a major step in the construction of the highway.

It is the province's first super long spiral tunnel.

According to Power China Road Bridge Group Co, the primary contractor for the project, the construction of one lane of the tunnel was completed at the end of 2019. Construction of the other lane started in early March, after being delayed by the coronavirus epidemic.

A road map of the Mide Tunnel on the Jiangeyuan Highway. [Photo provided to chinadaily.com.cn]

Jiao Yongliang, project manager for civil engineering on the highway, said various difficulties were encountered since the start of work because of complex geographical conditions. The project was considered the province's most difficult road construction project.

The Jiangeyuan Highway is expected to be fully operational in 2021.

An interior view of the Mide Tunnel on the Jiangeyuan Highway. [Photo provided to chinadaily.com.cn]