In pics: World's longest sea crossing bridge opens to public in China

The world's longest sea bridge opened to the public on Wednesday as busloads of Chinese tourists headed to the former colonial enclaves of Macau and Hong Kong.

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Hong Kong-Zhuhai bridge is now the world’s longest sea bridge with a 55-kilometre stretch between Hong Kong, Zhuhai on the mainland, and Macau — that has a nine-kilometre underground stretch as well

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Passengers take the shuttle bus to cross the China-Zhuhai-Macau-Hong Kong Bridge during the first day operation of the world's longest cross-sea project.

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The bridge has been built in nine years and is part of Beijing’s continued effort to drag the autonomous regions of Hong Kong and Macau closer to its orbit, as well as develop relatively under-connected locations within the Pearl River Delta megacity. All three cities connected will now be an hour’s commute from each other

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Those who want to cross the bridge must obtain special permits, allocated by a quota system. And all vehicles will pay a toll. The bridge is not served by public transport, so private shuttle buses will ply the route. There is no rail link. Authorities initially estimated that 9,200 vehicles would cross the bridge every day. They later lowered their estimations after new transport networks were built in the region.

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Special cameras will be on the look-out for drivers on the bridge who show signs of getting sleepy, among other checks - yawn three times and the authorities will be alerted, local media report.

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Since construction began in 2009, the project was postponed by construction delays, legal challenges and budget overruns. Environmentalists also warned the bridge would have a devastating impact on a remarkable and already critically endangered species of pink dolphin in the Pearl River estuary.