Despite Victoria paying billions of dollars to private operators over the past two decades in a bid to improve reliability, an ageing train network plagued by signal and equipment faults is straining under the weight of demand. There are 237 million people using the metropolitan network a year, up from 130 million people in 2000. Meanwhile, there are 300 more services on the metropolitan network, and 600 more on V/Line. The Age has analysed data from Public Transport Victoria that shows delays have become more frequent on some of the network's busiest lines. Nearly one in 10 trains on the Craigieburn line did not arrive on time last year. Back in 2001, 96.5 per cent of trains were punctual.

On the Cranbourne line, 93.3 per cent of services arrived on time in 2001, but this fell to 87.7 per cent by 2017. On the Werribee line, 95.8 per cent of services were punctual 17 years ago. In 2017, 91.6 per cent of services arrived on time. The only train lines to maintain their level of punctuality over the 17 years were the Glen Waverley (96 per cent) and Sandringham (95 per cent) lines. A train is considered late if it arrives more than four minutes and 59 seconds behind schedule. Before 2009, it was late if it arrived after five minutes and 59 seconds. Train reliability, which measures the proportion of scheduled trains that are delivered, went backwards on eight train lines.

On the regional V/Line network, six lines including the Ballarat, Bendigo and Geelong lines, were less punctual and less reliable in 2017, compared with 2005. (The analysis only goes as far back as 2005 and excludes the Albury and Swan Hill and Echuca lines, due to inconsistencies in the data.) The state paid $1.9 billion to Connex over five years from 2004, before Metro signed a $3.8 billion seven-year contract in 2009.

Victoria is now paying $6.3 billion to Metro over the next seven years. The company will be paid $330 million annually for maintenance and renewal works – a rise of 32 per cent. Commuter Stephen Colebrook is fed up with enduring constant delays during peak hour on the Altona Loop – a section of single track that veers off the Werribee Line between Laverton and Newport. The frequency of trains on the loop are limited due to the single track, and the loop is often bypassed when trains are running late, he said. The government is partially duplicating the track – an 800 metre stretch – but Mr Colebrook said this was just a small section of track. "It's really frustrating and the bypasses often happen at peak hour."

Melbourne University transport expert John Stone, who has led research tracking government funding to private rail operators, said the public deserved to know how Metro Trains was spending taxpayers' money on infrastructure. But this isn't made publicly available, Dr Stone said. "We are paying more to operate the network now than we ever did before ... but we can't tell where the money is going," he said. Dr Stone said patronage growth has been predicted "for at least the past decade" and was not a sufficient excuse for declining performance. "The public has a right to expect better punctuality and reliability than we currently get," he said.

Public Transport Minister Jacinta Allan said the government was delivering the most significant overhaul to the public transport system in the state's history, investing $30 billion to boost capacity and reduce congestion.

"After four wasted years under the former Liberal government – who didn’t start a single major transport project – we’re building the transport system to get Victorians where they need to go safer and sooner," she said. Getting Melbourne's trains to arrive on time is not a new problem, nor one that is unique to Metro Trains. Punctuality across the network dropped steadily under the previous operator, Connex, to between 86 and 88 per cent of services arriving on time. This was in the face of a 12 per cent annual increase in patronage between 2006 and 2008.

Punctuality rose above 90 per cent from 2012 under Metro Trains, and has hovered around 92 per cent since. Metro spokesman Marcus Williams said the company had made this improvement to train punctuality "against a backdrop of huge increases in patronage". "We are now in a period of massive investment that is modernising the network by adding capacity and building brand-new infrastructure," he said. PTV chief executive Jeroen Weimar said the number of services had "dramatically increased" over the past decade, "despite the overall design of our rail networks remaining largely unchanged". He said the Metro Tunnel (a new underground rail line being built under central Melbourne), the removal of level crossings and a $1.57 billion plan to improve regional rail services would deliver a boost.

Rail Futures Institute president John Hearsch said urgent improvements were needed on the network, such as extending the Cranbourne line to the suburb of Clyde and duplicating the single section of the track. Mr Hearsch said 50-year-old signalling and the use of the old trains built by Comeng that first entered service in the 1980s were contributing to worsening reliability. Increasing dwell times due to overcrowding was also causing a drop in punctuality, he said. "As soon as you have that [an increase in dwell time], those delays tend to cascade." In 2016, Victoria's Auditor-General found that the condition of both train and tram infrastructure had deteriorated in the seven years leading up to the audit.

But the problem was not being monitored properly by PTV, the Auditor-General said.