A bridge-tunnel linking China's third largest island, the Chongming Island, opened to traffic on Saturday.

The 25.5-kilometer project, with a cost of 12.6 billion yuan ($1.8 billion) includes a 8.9-kilometer tunnel that boasts the world's largest diameter of its kind, according to Huang Rong, director of the Shanghai municipal committee of urban-rural construction and communications.

It will take about only 20 minutes' drive from the booming Pudong New District of Shanghai to the 1,267-square-kilometer Chongming Island, Huang said.

"After the bridge opens to traffic, Chongming will embrace a historical opportunity of development," said the excited Peng Chenlei, Communist Party chief of Chongming.

Another tunnel from the island to northern Jiangsu Province is under construction.

The bridge-tunnel could help boost economy in the northern parts of the Yangtze Delta, said Yu Hongsheng, a professor with the Shanghai Academy of Social Sciences.

"It also provides a chance for restructuring the industries in Shanghai," he said.