Waterfall is where the South Coast line joins the Illawarra line, entering the Sydney rail network.

Transport for NSW has released the Review of Environmental Factors (REF) for the work at Waterfall, which will aid in passenger trains being able to pass slower freight trains.

At present there is a 850-metre freight loop to the west of the station, which rejoins the main line at the Waterfall platform.

The planned work will look to extend that loop to accommodate freight trains as long as 1500 metres.

"The extension of this loop would allow all freight trains to stop in the loop and be overtaken by faster Intercity South Coast services in the city-bound direction," the REF stated.

"This would facilitate improvements to off-peak passenger services on both the T4 Eastern Suburbs and Illawarra, and South Coast lines."

READ MORE: Intercity trains too long for Illawarra platforms

The planned work would address the current strain on the South Coast line, the REF claimed, which has "average passenger loads exceeding the seating capacity by 22 per cent, which is the second highest in terms of overcrowding across the intercity network."

The work at Waterfall station also includes the lengthening of the island platform by around 40 metres to accommodate the 10-car New Intercity Fleet.

The station is one of six on the South Coast line Transport for NSW plans to extend to fit the longer trains.

Depending on planning approval, work on Waterfall station will start late in 2019.

The community consultation over the plans - available on the Transport for NSW site - is open until September 6.