Transport for NSW has issued a statement warning commuters to expect long delays today, due to continuing industrial action.
A weekend frequency will operate on the Blue Mountains, Central Coast and Newcastle lines.
A heavily reduced train service will operate on the Sydney Trains and NSW TrainLink Intercity network due to the ongoing industrial action.
Friday's disruption is due to protected industrial action by the Rail, Tram, and Bus Union which involves not operating services using Waratah, Millennium, or OSCAR train sets, Transport for NSW said.
This represents about 70 per cent of the fleet used to provide more than 75 per cent of train services per day across Greater Sydney, the Illawarra, Blue Mountains, Central Coast and Newcastle.
The Rail, Tram, and Bus Union has had a two year dispute with the state government over the safety of new trains.
Transport for NSW has opened all transit lanes to all motorists to help with extra traffic on the roads. This means if you travel in a T2 or T3 lane you will not be fined.
Earlier this week the government agreed to spend $264 million dollars on modifications to the trains but the RTBU later issued a statement that said: "The NSW Government conceded it needs to fix the safety issues on the NIF [New Intercity Fleet] Trains. Unfortunately, however, we've heard promises from the NSW Government before, so the union needs to see the complete package before any industrial action can be called off."
The union wants the offer in writing.
"We still don't have any signed documents that we can go out to our members with and have a conversation about reducing any sort of industrial action," RTBU Secretary Alex Claassens told the ABC.
The impact of limited train services coupled with the start of school holidays means the Sydney Airport stations and the roads will be busier than usual. Anyone travelling to the Airport stations is urged to not travel by train and to allow extra time.
Transport for NSW has opened all transit lanes to all motorists to help with extra traffic on the roads. This means if you travel in a T2 or T3 lane you will not be fined.
Sydney Trains Chief Executive, Matt Longland, said commuters should plan their journeys and allow extra time with delays, cancellations, and a significantly reduced timetable in operation today.
"I'd like to thank our customers for their patience so far this week and assure them we are doing our best to limit disruptions and run services safely as we continue to work with the unions to reach an agreement," Mr Longland said.
"We will be doing our best to maintain a frequency of service across the network for commuters who really need to use the rail network, but we are asking our customers to avoid non-essential travel and consider other options, especially for places such as the airport which will be busy heading into the school holidays."
NSW TrainLink Chief Executive Dale Merrick said rail customers in outer metropolitan areas will also face disruption and also urged commuters to delay non-essential on regional trains.
For the latest traffic updates visit livetraffic.com or download the Live Traffic NSW App. Transport for NSW is urging travellers to check transportnsw.info for the latest service impacts.
WEATHER
Meanwhile in other breaking news, parts of NSW are in for a very wet weekend, with consecutive days of heavy rainfall forecast. River rises are possible and there is potential for flooding.
The Bureau of Meteorology is asking people to consider their travel plans for the holidays and monitor forecasts and warnings: www.bom.gov.au/nsw/warnings/. For emergency assistance in floods and storms, call the NSW SES on 132 500. In life threatening emergencies, call Triple Zero (000) immediately.