Labor's plan to unclog Sydney roads

Federal Labor is promising to unclog key Sydney roads if elected by shifting more freight containers onto rail.

The opposition is pledging to duplicate the freight line between Port Botany and Mascot at a cost of $108 million.

It will also establish a rail crossing loop at Warwick Farm, in the city's west, at a $67 million cost.

The funding would be in the form of an equity injection to the Australian Rail Track Corporation, with the projects finalised by 2023.

Labor leader Bill Shorten said it would take 300,000 trucks off Sydney roads a year.

However, there are no guarantees with Infrastructure Australia yet to assess the business case.

Mr Shorten will make the announcement on Wednesday with Labor MP Matt Thistlethwaite, whose marginal Kingsford Smith electorate includes Port Botany.

Labor is keen to stave off a potential strong Liberal challenge from Michael Feneley who needs just a 2.7 per cent swing to win the seat.