The NSW premier has apologised to passengers caught up in last week's Sydney train chaos and admitted more should have been done ahead of time to prevent the system meltdown.
Almost 40 train services scheduled to run through Monday were cancelled ahead of the morning and afternoon peaks to avoid a repeat of last week's debacle that left thousands of passengers stranded.
The meltdown was due to a combination of storms, trackwork, a spike in sick leave and "excess" annual leave approvals.
"With the benefit of hindsight we should have taken proactive action and reduced the number of services that day (Tuesday) and let customers know, so that those delays weren't experienced," Gladys Berejiklian told reporters in Sydney.
"I want to wholeheartedly apologise to all of our customers. The system most days is world class and some days, unfortunately, we let commuters down."
Ms Berejiklian revealed that if "permanent tweaks" were needed to Sydney's new more intensive train timetable "then we'll make them".
The boss of Sydney Trains assured passengers that staff were doing everything possible to keep trains moving on time on Monday.
"A very small number of cancellations have taken place (but) for the morning peak about 96 per cent of our service ran to schedule," chief executive Howard Collins told reporters.
Some 36 services were cancelled with buses called in as back-up.
Travellers on the busy North Shore and Eastern Suburbs and Illawarra lines also faced delays due to urgent signal equipment repairs at Milson's Point and Central respectively.
The NSW government blamed last week's meltdown on drivers calling in sick and storm damage but it was later revealed management had also approved "excess" annual leave.
Rail bosses met with the Rail, Train and Bus Union on Thursday to discuss the problems ahead of what was termed a "pressure day" on Monday.
"It's ridiculous that in a city like Sydney we have a timetable that is so poorly designed that it may struggle to get commuters to and home from work on Monday because of these foreseen events," RTBU NSW secretary Alex Claassens told AAP in a statement.
"We've been warning for months that this timetable won't be able to cope with even minor issues and that the smallest of incidents could send the network into chaos."
Rail workers on Friday voted in favour of industrial action as they continue to fight for a six per cent pay rise and improved working conditions but have stopped short of going on strike.
Workers will instead wear campaign clothing and badges from Friday and, from the following Thursday, implement an indefinite ban on overtime.
The union will meet with Sydney Trains management on Tuesday to discuss the new train timetable implemented in November before meeting chief executive Howard Collins on Thursday regarding the enterprise agreement.
Mr Collins said if drivers refused to work unplanned or rostered overtime it could cause fresh chaos.
Transport Minister Andrew Constance said he hoped workers wouldn't strike and the government wanted to negotiate in "good faith" with the union.