Within about one kilometre of Sydney Airport, Mascot's town centre is becoming a motorist's nightmare. Cars crawl along streets lined with new apartment buildings.

Within a few years about 7000 new dwellings are forecast to be crammed into a 30-hectare area in the suburb in Sydney's south, piling more pressure on local roads.

Apartment buildings now line many streets in Mascot and surrounding suburbs. Credit:Kate Geraghty

And leaked documents marked "Cabinet in confidence" reveal the congestion looming for roads at Mascot and other suburbs neighbouring Australia's busiest airport and second-busiest container port, dubbed the country's gateway to the world.

After an interchange for WestConnex at St Peters in the inner west opens in the next two years, about 75,000 vehicles a day are forecast to be funnelled from both it and other roads through Mascot to the airport, port and other areas in the precinct.