Overcrowded carriages also make it more difficult for trains to run on time, because of the longer stopping times needed to load and unload passengers. In a sign of the pressure on the system, patronage on the suburban rail network is growing at 7 per cent a year, compared with the historical growth rate of 1.2 per cent per annum. In the past five years, train patronage has surged by 30 per cent. Major relief from crowding on trains and stations in the CBD is still four years away when the second stage of a metro train line is due to open. The $12 billion line will run from Chatswood in the north, under Sydney Harbour to the CBD and into Sydenham and Bankstown. Trains on the T8 Airport Line also recorded average loads of 132 per cent in September last year, compared with 126 per cent in the same month a year earlier.

The Airport line is under pressure from an influx of people moving into high-rise apartments at Green Square and Mascot in the inner south, and greater demand for trains to and from Sydney Airport. Trains on three lines – the T1 Northern via Strathfield, the T1 Western and the T5 Cumberland – each had passenger loads during the morning peak in September as high as 180 per cent. Mathew Hounsell, a researcher at the University of Technology's Institute for Sustainable Futures, said pressure would intensify on the city's existing rail network over the coming years despite the opening of new metro train lines. Town Hall train station suffers from crowding at peak hour. Credit:Ryan Stuart "The increase in housing across Sydney's rail lines will put even more strain on the system in a few years time," he said. "Every additional person moving into an apartment in Sydney is going to be looking for a public transport option."

Mr Hounsell said average loads of 154 per cent on the T5 Cumberland Line in September showed that Parramatta needed to become an immediate focus of transport investment. "If Sydney doesn’t invest in high capacity public transport, we risk our overcrowded buses and trains stalling our economic growth," he said. The Berejiklian government has committed $6.4 billion to a new rail line carrying metro trains between central Sydney and Parramatta, and promised to start construction next year. However, reprieve for commuters using one of the lines most under pressure, the T1 Western, is years away because the new metro line is not due to open until the second half of next decade. The cost of Sydney Metro West is expected to near $20 billion.

The figures from Transport for NSW record passenger loads on trains travelling towards Central Station during the morning peak. Loading The average number of passengers carried on trains between 8am and 9am across all suburban lines – including the T5 Cumberland in the west – last September was about 117,000 a day, compared with almost 108,000 in the same month in 2017 and almost 101,000 in 2016. Town Hall is one of the stations under acute pressure. Passengers passing through the CBD station's gates reached 68 million in the 12 months to June last year, a 23 per cent rise on the 55 million passengers in the 2015-16 financial year. That equates to about 13 million extra passengers at Town Hall. The crowding on trains is also likely to explain why Sydney Trains has failed to meet its punctuality targets for the past three months of at least 92 per cent of services arriving within five minutes of its scheduled time during the morning and evening peaks.