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

Vehicles pass through the Shanghai Yangtze Bridge-tunnel on October 31, 2009. [Xinhua]

The 25.5-kilometer project, with a cost of 12.6 billion yuan, 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.

The island takes up one sixth of Shanghai's territory and is home to five percent of the city's population. But its Gross Domestic Product (GDP) is just one seventieth of Shanghai's average.

"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.