The head of the legislature's transport panel said Hong Kong authorities should have a careful think about the road network's capacity to cope with increased traffic when a scheme allowing cars from Guangdong to travel to the SAR is eventually expanded to cover urban areas.

Local officials have said they plan to announce details of the southbound travel scheme this year once they nail down proposals and implementation details with their mainland counterparts.

Lawmaker Chan Siu-hung said he understands the first stage of the scheme would see Guangdong drivers allowed to drive to a carpark on the Hong Kong-Zhuhai-Macau Bridge.

Drivers and passengers would then be able to go to the airport or travel to other parts of Hong Kong from there using other modes of transport.

The second stage, Chan said, would allow cars to enter urban areas.

He thinks that could be a public concern and much of that would hinge on the authorities' decision of where else Guangdong drivers would be allowed to get to in their cars.

"When it's about the urban areas, people are rather nervous about it," Chan said on RTHK's "In the Chamber" programme.

"Because if you talk about travelling to places like Mong Kok or Causeway Bay, our road network won't be able to cope with [the extra traffic].

"So I think the priority is to control the volume of traffic in the first stage of the scheme, and then define what would be the urban areas for the second stage."

Chan said officials from both sides of the border are aware of congestion issues on the Hong Kong-Zhuhai-Macau Bridge during festive periods, and he recommended solutions such as adopting a quota system.

However, he stressed that increased traffic flows from across the border can help local economic development.