Sydney Trains cannot rule out future peak-hour delays and disruptions, as a major incident review on last month's system meltdown is released.

The recommendations: Reviewing strategies for dealing with "high impact" network incidents in a complex, tangled network

Reviewing strategies for dealing with "high impact" network incidents in a complex, tangled network Providing extra capacity for incident recovery by using reviews of the timetable to look for opportunities to adjust non-peak services used by an extremely low number of customers

Providing extra capacity for incident recovery by using reviews of the timetable to look for opportunities to adjust non-peak services used by an extremely low number of customers Accelerating recruitment of new drivers

Accelerating recruitment of new drivers Working with unions to help simplify changeovers for crew

Working with unions to help simplify changeovers for crew Bringing in an independent expert to improve systems to put the right number of crew where they are needed

Bringing in an independent expert to improve systems to put the right number of crew where they are needed Updating support and IT systems to ensure better communication and crowd management

The report, commissioned in the wake of two days of train chaos last month, found the city's "tangled" rail network and crew shortages were major factors in the debacle.

"Can we guarantee its going to be perfect every day?" chief executive Howard Collins said.

"I think as everyone gets out of bed everyday sometimes things go wrong.

"What I'm expecting to happen and we're working on hard is building that resilience to minimise the impact of major delays."

Thousands of commuters were left stranded on January 8 and 9 as trains stopped and passengers were turned away from platforms at Central and Wynyard due to overcrowding.

The report Transport for NSW and Sydney Trains was released this morning and contains recommendations to accelerate the recruitment of drivers, and to work with unions to simplify crew changeovers.

A timetable board at Central Station tells the story on January 9. ( ABC News: Clare Blumer )

Mr Collins said some non-peak hours services would be reduced to free up resources.

"We need more driver resources to allow us to recover this timetable," he said.

"It's a very intense service, it's quite complex.

"We are recruiting and moving those resources into the organisation and I expect over the next few weeks we will be making minor adjustments to the services."

Mr Collins said Sydney Trains was investing $1.5 billion into the rail network, including infrastructure upgrades and 24 new trains that will replace the aging S-set trains.

Action needed to avoid a repeat

The report examined the rail network's ability to recover from major incidents.

Transport secretary Rodd Staples said network incidents and triple lightning strikes were the catalysts for the disruptions, but the report showed the network was vulnerable because of two underlying issues; the rail network is "complex and tangled, which means when things go wrong, flow on effects can be crippling", and a lack of drivers.

Transport Minister Andrew Constance said he would work to enact all the recommendations of the report.

Opposition transport spokeswoman Jodi McKay said commuters would continue to face chaos and confusion without major changes to the timetable.

"They [the Government] are basically softening everyone up saying 'This is now the new normal, you can expect an inferior service into the future', and I don't think that is good enough," she said.