The Northern Expressway in the South Australian city of Adelaide will open three months ahead of schedule due to a financial boost under the federal government’s economic stimulus plan.

The announcement was made during the opening of the 90m Port Wakefield Road Bridge, one of the 15 bridges along the 23km expressway.

The government has allotted $451.2m towards the $564m project, which will link the Sturt Highway with Port Wakefield Road.

The new expressway is expected to reduce travel time between Adelaide and the north by about 20 minutes and will be open from 13 September.