The world’s longest sea bridge, connecting Hong Kong and Macau to the Chinese mainland has been officially opened, in a ceremony in Zhuhai attended by Chinese president Xi Jinping and Hong Kong’s chief executive, Carrie Lam.

In a short address Xi declared the bridge open, as digital fireworks exploded on a screen behind him. The bridge will open to traffic on Wednesday.

As well as being the longest bridge of its type, stretching 55km, the $20bn Hong Kong-Zhuhai-Macau bridge is also one of the world’s most unusual roadways, with cameras to detect yawning, drivers forced to wear heart monitors and access restricted to the political elite and charity donors. Here are five things you need to know about the crossing:

‘Yawn cams’ and blood pressure checks

World's longest sea bridge to open ... but only to drivers with a special permit Read more

As drivers cross the bridge their heart rate and blood pressure will be monitored. The information will be sent to the bridge’s control centre. Hong Kong media have also reported there will be cameras monitoring drivers as they cross the bridge. If a driver yawns more than three times in 20 seconds, the “yawn cam” will raise an alert.

Special permits

Though the bridge aims to bring the autonomous regions of Hong Kong and Macau closer to mainland China, it will be accessible only to a select few.

People from Hong Kong will need special permits to drive across the bridge. There are reports that long-term permits to cross from Hong Kong to Zhuhai will be granted to people who meet strict criteria, such as paying significant taxes in China, donating large amounts of money to charities in the southern Chinese province of Guangdong, or those who are members of one of several political organisations. Others can take a private shuttle bus. There is no public transport on the bridge.

Controversy

Online commenters in Hong Kong have complained about the bridge’s restricted access. “Such a huge investment using the Hong Kong taxpayer’s money... yet basically it is not open to us at all,” said one comment on the South China Morning Post website.

Facebook Twitter Pinterest A policeman and his dog patrol at the immigration building for the China-Zhuhai-Macau-Hong Kong Bridge ahead of the opening ceremony in Zhuhai Photograph: Andy Wong/AP

Pro-democracy lawmaker Eddie Chu described the bridge as a “politically driven mega-project without urgent need.” Another bridge is being built between nearby Shenzhen and Zhongshan, just north of Zhuhai, meaning that by 2030 traffic is predicted to drop significantly on the Hong Kong-Zhuhai-Macau bridge. “Basically it is redundant,” he said.

Which side?

In Hong Kong and Macau, drivers travel on the left, in mainland China, drivers travel on the right, presenting a bit of a conundrum for the bridge.

Since the bridge is considered mainland Chinese territory, drivers will have to travel on the right for the length of the crossing, and Hong Kong drivers will also have to “comply with the laws and regulations of the mainland” while on it, according to the city’s transport department.

While creative solutions were put forward about how to handle the side swap, including a “flipper bridge” called the Pearl River Necklace proposed by a team of Dutch architects, a less exciting approach was chosen in the end, with cars stopping and changing sides at a specially built merge point before they drive onto the bridge in Hong Kong.

Bridge politics

The bridge is part of a campaign to connect Hong Kong and Macau to 11 Chinese cities to form a high-tech region to rival Silicon Valley, the Greater Bay Area. It is also the second major infrastructure project tying Hong Kong to mainland China to launch in a matter of weeks after the opening of a high-speed rail link last month.

Critics say the multi-billion dollar bridge is an attempt to integrate Hong Kong into China as fears grow that the city’s cherished freedoms are being eroded. Both Hong Kong and Macau are part of China, but are special administrative regions, which have their own governments, legal systems, and policies. There are concerns this bridge is a sign of Beijing’s desire to bring the regions more firmly under its control.