This is due to the fact the South Coast line joins the Illawarra line at Waterfall.

The Auditor-General’s report found  trains on this line were crowded before the 2013 timetable change.

That revamp removed stops along the Illawarra line for peak service to deal with the overcrowding.

“This is an indicator that the Illawarra line is close to or has exceeded its capacity to run more trains,” the Auditor-General’s report said.

This will undoubtedly have a flow-on effect for the South Coast line, which a Transport for NSW spokeswoman said shares capacity on the Illawarra line between Waterfall and the CBD.

The spokeswoman said the Illawarra line was at capacity during the morning and evening peaks.

“In addition, the NSW Government’s long-term plan to transform the rail network, called Sydney’s Rail Future, makes clear the need to boost capacity on this line,” the spokeswoman said.

“Planning work is now under way to look at travel patterns and demand in the Illawarra to help determine how to best meet future capacity in the south, when it’s needed.”

The spokeswoman said future enhancements to the South Coast line may require a combination of measures to improve capacity, including significant investment in new services and upgrading existing infrastructure.

The report also looked at TfNSW’s punctuality marker,  the Customer Delay Measure (CDM).

This is a measure in minutes and seconds of the time difference between a customer’s expected arrival (as per the timetable) and their actual arrival.

The monthly measures from July 2015 to April 2016 show South Coast line services meeting their targets.

However, in the afternoon peak the target was met in only one of the 10 months, with a CDM of 8:52 the worst.

The spokeswoman said the afternoon peak was “more likely to be impacted by flow-on effects of delays on the rail network during the day”.