A new fleet of double-decker buses and new public transport routes have been announced by the NSW government ahead of the state budget.

About 3800 extra weekly services will be added, as part of a $108 million investment in new buses, including 12 new or extended routes throughout Sydney.

Up to 12 double-decker buses will carry passengers on key corridors, including the Rouse Hill-City service, between Blacktown and Macquarie Park and on the Liverpool-Parramatta transit, the state government announced on Tuesday.

Improvements to Macquarie Park services will be welcomed by the growing tech hub's commuters. According to analysis by Savills Research earlier this year, Macquarie Park (886,499 square metres) has more commercial space than North Sydney (820,747 square metres), making it Sydney's second biggest CBD and Australia's fourth biggest by workspace.