As a researcher working for a medical institute in Zhongshan, Guangdong province, Yang Nan needs to visit Shenzhen for academic exchanges frequently, usually by driving for more than two hours.

"There were always traffic jams on the highway, although the distance between Shenzhen and Zhongshan is not much," said Yang.

The transportation situation between Zhongshan and Shenzhen, located in the western and eastern estuary of the Pearl River, respectively, improved significantly since Sunday. It now takes less than one hour for a cross-city bus between the two cities along the newly opened Shenzhen-Zhongshan Link.

The link, a mega cross-sea passage integrating bridges, islands, tunnels and underwater interchanges in the Guangdong-Hong Kong-Macao Greater Bay Area, began its trial operation on Sunday, after seven years of preparatory work and challenging construction.

After the passage is opened, the journey from Shenzhen to Zhongshan would be reduced from two hours to just 30 minutes.

"The opening of the passage is truly convenient for transportation between Shenzhen and Zhongshan, and I will choose to drive or take cross-city buses to visit Shenzhen frequently," said Yang.

Along with the opening of the passage, local transportation authorities have also launched two cross-city bus routes between Shenzhen and Zhongshan,

Both bus routes TO1A and TO1B, from the expo center and Cuiheng new zone in Zhongshan to Shenzhen's Qianhai Bay subway station, reached their maximum capacity on Sunday, with all tickets sold out, according to Zhongshan Public Transportation Group Co Ltd.

On Sunday, the passage's construction companies also arranged eight special vehicles to transport nearly 400 representatives and family members of the builders, allowing them to experience in advance the project they had personally contributed to.

After spending eight years on the construction of the Hong Kong-Zhuhai-Macao Bridge, Sun Yuenan, a female engineer, was transferred to work for the Shenzhen-Zhongshan project four years ago.

"I am very fortunate to have been involved in the construction of these two super projects, witnessing historic moments of China's bridge construction and development," said Sun, who took a chartered bus to go from Zhongshan to Shenzhen through the passage on Sunday.

In addition to the operation of cross-city buses between Shenzhen and Zhongshan, a total of nine routes connecting Guangdong and Hong Kong, with 92 trips in total, will pass through the Shenzhen-Zhongshan passage, further facilitating travel in the Greater Bay Area, according to Luo Chengzhen, general manager of the Guangdong-Hong Kong Joint Bus Transportation Company Limited.