Residents of Sydney's northern beaches will be able to catch new double-decker buses to and from the city centre once the state government opens its $516 million B-Line rapid bus route in the next few weeks.

While the project still faces opposition, Transport Minister Andrew Constance said the B-Line bus services would "be a winner" and came against the backdrop of the government's plans to build a second road tunnel under Sydney Harbour and the Beaches Link between the Warringah Freeway and Balgowlah in the city's north.

"We are looking to get services up and running in the next few weeks. It's a project which is delivering 38 double-decker buses to provide a reliable turn-up-and-go service to the people of the northern beaches," he said.

"The most exciting element of this program is commuters travelling home after seven o'clock are going to have a bus service every 10 minutes."