One of the two passages of the underground Shangzhong Road Tunnel will be open for traffic before the end of January, the city's transport commission said yesterday.

The tunnel will run under the Huangpu River, linking the Puxi and Pudong sections of the Middle Ring Road, the commission reported.

The two-level vehicle tunnel is a key traffic development as it leads into the World Expo zone in Pudong.

The Middle Ring Road's section in Pudong is still being built and is expected to open before the end of next year, according to the local construction commission.

The second passage is planned to open for traffic in March, officials said yesterday.

The first passage to open will be the south passage, designed to serve traffic flowing from Puxi to Pudong. However, it will temporarily be used for two-way traffic until the other passage comes into service, officials said.

Construction officials also said another underground tunnel is being built to link the Jungong Road Tunnel to the Pudong section of the Middle Ring Road. The project will be finished in 2011.