Melbourne needs 110 new bumper-sized trams by 2020 to avoid chronic overcrowding and to address public safety concerns caused by the ageing tram network, Yarra Trams says.
Yet the Napthine government has committed to adding just 50 extra trams to the network in the next four years, and is yet to secure all of the land it needs for new electrical substations that must be built to power the larger, modern trams.
The government needs to build 16 new substations at various locations around the tram network in order to inject the necessary grunt to power the 50 E-Class trams it has ordered, but Fairfax Media has learnt it is yet to identify or secure the land for five of them.
A site in Preston at the terminus of tram route 112 must be found "urgently" if the government is to make good progress on its rollout of the E-Class trams, which can carry 210 passengers each, Yarra Trams says.
The identification of substation sites at St Kilda Road, St Kilda Beach, Lygon Street and Nicholson Street also must be "fast-tracked" to give tram routes on those streets the power to handle a greater number of high-capacity trams, the operator says.
Public Transport Victoria spokeswoman Helen Witton said: "Land has been secured for nine substations and significant progress has been made in identifying appropriate land for the remaining five."
The city's looming tram capacity crisis is being exacerbated by the impending need to retire 147 old Z-Class trams that still make up a large percentage of Yarra Trams' fleet but which have officially passed their expiry date.
The 1970s-era trams have capacity for just 70 passengers and struggled badly in Melbourne's recent summer heatwave, when dozens were forced out of service.
Rail, Tram and Bus Union divisional secretary Phil Altieri said the trams were hopelessly ill-equipped for the transport task.
"All were meant to be retired after the 2006 Commonwealth Games but there was a patronage spike and they're still running around. They've had very little work done on them because the government doesn't want to spend money on old vehicles that are past their use-by date," he said.
Earlier this month a Z-Class tram damaged a car when a tram lifeguard, designed to prevent people being caught beneath the wheels, fell off and crashed into the vehicle's tyres.
Mr Altieri said it was one of three incidents in the past month in which public safety was put at risk by malfunctioning tram infrastructure.
"We conclude that Yarra Trams is not maintaining the system; the numbers are unprecedented and we can only assume that something is not being done by this company," Mr Altieri said.
The union has images of a broken tram floor plate that was damaged when a tram point dislodged from the tracks and speared into the bottom of the tram on June 17. No one was injured on that occasion, although a woman was injured in an earlier incident in May when a tram floor plate dislodged and crashed into her legs. An ambulance attended the scene.
Yarra Trams is investigating all three incidents, but said "there is no evidence of any systemic issues across the fleet or the network".
Z-Class trams are inspected every two weeks as part of an annual $65 million investment in tram network maintenance.
The plan to steadily phase out all Z-Class trams by 2020 hinges on the procurement of 110 new E-Class trams by the same deadline. Manufacturer Bombardier has a contract to build 50 new trams by 2017, with an option for a further 100. Just five of the new low-floor trams are in service, operating on route 96 between Brunswick East and St Kilda Beach.
State transport authority Public Transport Victoria has a plan to "cascade" other low-floor, high-capacity trams on to other busy routes as more E-Class trams roll out.
As of January, patronage on 13 of Melbourne's tram routes exceeded capacity.
Those in line to get an entire fleet of newer trams before the decade's end are route 19 between Elizabeth Street and Coburg North, route 11 between West Preston and Docklands, route 12 between St Kilda and Richmond, route 86 between Bundoora and Docklands, route 48 between North Balwyn and Docklands and route 72 between Melbourne University and Camberwell.