"We're going to see a network that's busier across the day than ever before and it will be a bit more fragile, so when things go wrong it will have more of a cascading effect," Dr Clifton said. "New York is a warning for Sydney, they didn't keep up with the investment as numbers were growing, and the quality of service there has deteriorated so much that the number of people using the subway is dropping, and people are forced to look for alternatives like Uber." Investment in buses and light rail will take pressure off the train network, but, improving public transport brings more people to it, so more investment will be needed to keep up with growing demand, Dr Clifton said. "The government is doing some good things like opening up new entrances to stations such as at Redfern to help the network cope with bigger numbers," Dr Clifton said.

The NSW Auditor-General reported there were six lines where passenger crowding was above the benchmark in March 2018 and Rail, Tram and Bus Union NSW Secretary Alex Claassens said overcrowded trains can become a "significant" safety issue. "Not only does overcrowding cause considerable stress and discomfort for passengers, but it also increases the risk of things like crushing and puts passengers and workers at increased risk in the event of an emergency situation," Mr Claassens said. “For a year now, Sydneysiders have been thrown into commuting chaos because of a network that has no contingency room and is forcing more commuters to take multiple forms of transport just to get from A to B." NSW Transport Minister Andrew Constance said network growth of 30 per cent over the past five years is set to continue. "In November 2017, the NSW Government introduced a new train timetable with around 1,500 extra weekly services, including 750 on weekends and 180 late at night in response to unprecedented demand," Mr Constance said.