The Shenzhen-Zhongshan link should have had a soft opening to reduce the mega infrastructure project's novelty factor, according to the CEO of a transport consultancy.

The new 24-kilometre link across the Pearl River Delta opened on Sunday but traffic was gridlocked as many drivers stopped on the bridge to take photos.

"In terms of the congestion we are seeing at the moment, those are just novelty factors," said Alok Jai, CEO of Trans-Consult, on RTHK's Hong Kong Today programme.

"And normally when we open infrastructure like that, usually you should have a soft opening - which gives people the chance to take pictures and look around and appreciate it - before you do the full opening, or proper opening, then it becomes a proper transport linkage."

Many people, including visitors from Hong Kong who took an inaugural trip over the link on Sunday, were stuck in the gridlock. One of them, lawmaker Gary Zhang, said it took him six hours to get from Kwun Tong to Zhongshan.

Jain welcomed the link, saying it would take pressure off the Humen Bridge at the north of the Pearl River Delta and improve connectivity within the region. But he said he didn't think it would cut journey times between Shenzhen and Zhongshan to 30 minutes from two hours, which had been widely reported ahead of the opening.

"It is certainly going to reduce it by 45 minutes or so. But that in itself - as far as we talk about the connectivity within the Pearl River Delta, or the Greater Bay Area - that is a significant saving in journey times," he said.

Jain also said he expected the new link to take traffic away from the Hong Kong-Zhuhai-Macau Bridge, which is more expensive. He said Hongkongers heading to Zhongshan may opt for the new link instead of going via Zhuhai. But he said the main beneficiaries would be those living in the Shenzhen or Zhongshan areas and those using the Humen Bridge.

The Shenzhen-Zhongshan link consists of two bridges, two artificial islands and an under-sea tunnel.