Prime Minister Scott Morrison will splash $70 million on traffic relief in a key Melbourne marginal electorate as he battles for the infrastructure vote before the federal election.

The Coalition will commit a major congestion-busting upgrade to bring relief to more than 20,000 motorists enduring chronic traffic delays on Pakenham’s Racecourse Road.

The road will be upgraded between the Princes Freeway and Henry Street, the Prime Minister will announce today.

Australian Prime Minister Scott Morrison commits $70m for roadworks in a key marginal seat. Credit:Richard Wainwright

The project includes new traffic light signals at the Bald Hill Road intersection, an upgraded freeway overpass and the duplication of a connecting road.