The state government has ordered 24 new eight-carriage trains to deliver "hundreds" of extra services including peak hour express services between Parramatta and the centre of Sydney, it said.
The state's rail infrastructure will also be upgraded, "allowing our ageing and complex network to operate at an even greater capacity, including better signalling systems, power supply upgrades and station improvements", it said.
Minister for transport and infrastructure Andrew Constance said the government had to act quickly to keep the train system running well.
"We've seen average train loads rise significantly, which is starting to impact on customers' ability to get on a train in peak periods," he said.