Demand is surging, putting extra strain on Sydney's aged rail network. Credit:James Brickwood The length of time a train needs to stop at a station when it becomes overcrowded is likely to blow out and cause the train, and others following, to run late. Trains running on the Illawarra Line via Sydenham and Hurstville in the city's south recorded average loads of 136 per cent in the morning peak, according to the data collected in September by Transport for NSW. The third most crowded trains on Sydney's suburban network at peak hour were on the Northern Line via Strathfield. Trains on that line via Redfern had loads of 135 per cent. But what is striking is the rate of increase in crowding in just a year.

Average loads on the Western Line – the city's busiest – surged by 21 percentage points to 134 per cent between September 2014 and September 2015. Transport officials collect the train load data twice a year – in March and September. Passenger loads are usually higher in March, a month that also tends to be less affected by seasonal factors. In a sign of the rapidly increasing demand for public transport, all but one suburban and intercity line in NSW recorded higher loads in September. The greatest increase was on trains to the Central Coast, which had passenger loads of 121 per cent in September, up from 76 per cent a year earlier. A load factor of 100 per cent means the number of passengers on a train is equal to the number of seats.

Commuters can take some solace from the fact that trains are less crowded during the evening peak between 5pm and 6pm than in the mornings. Suburban trains running at that time had average loads of 90 per cent in September, compared with 89 per cent in the same month a year earlier. With patronage expected to continue to surge due to strong population growth in Sydney, any significant relief from overcrowded trains for commuters is still some time away. The first stage of a $20 billion-plus metro line from northwest Sydney to Chatswood is due to open in 2019. However, single-deck driverless trains are not scheduled to begin running on the crucial second stage under Sydney Harbour from Chatswood to Bankstown via the CBD until 2024.

The new 65-kilometre metro line – the first under central Sydney since the construction of the Eastern Suburbs line in the 1970s – is expected to significantly reduce crowding for commuters using stations such as Wynyard, Central and Town Hall. The government plans for the metro line to have a target capacity of about 40,000 commuters an hour, compared with the existing suburban network's 24,000. Transport Minister Andrew Constance said the government was building extra capacity on the train network "as fast as we can". "Not only are we building an entirely new metro line, but three new light rail lines," he said. Colin Schroder, from public transport advocacy group EcoTransit, said the crowding on trains highlighted a lack of investment in the rail network over the past 50 years.

"It is probably going to get more and more crowded on the trains, especially when they reintroduce the tolls on the M4 after the federal election," he said. "People will be looking for alternatives when it costs more to travel by car." Mr Schroder warned that the new metro line would not be a saviour for Sydney's rail network because he argued it would not boost capacity on the existing suburban lines. "There just isn't enough investment into the existing infrastructure to increase capacity," he said. A spokesman for Sydney Trains said average train loads on the network were increasing in a similar way to public transport systems in cities such as London, Paris and New York.

"We anticipate that through Sydney Metro, together with signalling and infrastructure upgrades across the existing network, we can increase the capacity of train services into the CBD from about 120 per hour today, to up to 200 services beyond 2024," he said. "That's an increase of up to 60 per cent capacity across the network to meet demand for our growing city."