China opened the world’s longest sea bridge on Tuesday, creating a direct road link between Hong Kong, Macau and the mainland city of Zhuhai.

The 34-mile (55 km) span across China’s Pearl River estuary was declared open by President Xi Jinping and is 20 times the length of San Francisco’s Golden Gate Bridge, according to The Wall Street Journal.

The six-lane bridge links up a region with a population of around 70 million. Construction cost about $20 billion and took nine years, with at least 18 workers dying on the job and hundreds getting injured during that time, the BBC noted.

Since ships use the waterway, there’s a 4-mile middle section where the bridge moves to an undersea tunnel that links a pair of artificial islands.

The bridge cuts the journey between Zhuhai and Hong Kong from four hours to 30 minutes, but not everyone will have access — private car owners looking to cross must have separate permits for each city, which are subject to a quota, and pay a toll.

Since cars in Hong Kong and Macau drive on the left and mainland Chinese drivers stay on the right, there’s a merge point where they switch sides, Wall Street Journal reported.

There’s no rail link and only private shuttle buses are allowed on. These will start operating on Wednesday.

The bridge will also be equipped with ‘yawn cameras’ that alert authorities if bus drivers seem too sleepy — three yawns and they’ll have to explain themselves, France 24 reported, citing Hong Kong media.