Melbourne's future will be one in which giant trams almost as long as Olympic swimming pools glide along crowded inner city streets where tram tracks were first laid for streetcars no bigger than an ordinary bus.

The next generation of trams will be an imposing 45 metres in length - 12 metres longer than the new E-Class trams that are being steadily rolled out and more than three times longer than the old W-Class trams that still rattle around the city centre.

One of the original 50 E-Class trams. Credit:Adam Chandler

Built to carry about 300 passengers, the jumbo trams are part of Public Transport Victoria's future plans to handle rapid patronage growth on Melbourne's tram system, which is increasing at 3.6 per cent a year.

Exactly when they will hit the network is unclear, but PTV could easily pull the trigger on their introduction. E-Class trams have a modular design that can be extended by adding a fourth compartment to their current three.