Metro's five-year plan includes a target to cut power use by 10 per cent for each kilometre of train travel - and ultimately by 20 per cent - to reduce its greenhouse gas emissions and save taxpayers' money. The state pays Metro's electricity bill under the rail operator's franchise agreement with the Transport Department. ''We have set a target of a 10 per cent reduction of traction electricity consumption per unit kilometre operated by 2017,'' the plan states. It aims to achieve this through the use of regenerative braking technology, which uses a train's motor and brakes to put power back into the overhead wiring to be used by other trains. But little progress has been made in the two years since it put the power-saving proposal to government, with the high cost and practical difficulty of applying the technology to Melbourne's rail system being blamed. Metro said a computer simulation on the hilly Lilydale line had shown the energy regenerative braking technology would save electricity.

''This showed that once the technology is affordable, a business case can be made so that it's commercially viable,'' spokeswoman Larisa Tait said. ''The technology is in its infancy and is currently very expensive and we are waiting for the cost of the storage units to reduce.'' Additionally, many of the electrical substations that help power the network and which were built in the 1920s when Melbourne's rail lines were first electrified are not equipped to handle regenerated electricity. The braking technology will also not work with Metro's Comeng trains, which make up more than a third of its fleet but are due to reach the end of their design lives between 2017 and 2024, according to Metro's plan. Tony Morton, president of the Public Transport Users Association, said Metro's power consumption was less efficient than it should be because Melbourne's rail network still used the same voltage system it began with. ''We still operate a 1920s vintage power-supply system for our trains,'' Dr Morton said.

''Fifteen-hundred volts DC was state of the art when it was first put in, but virtually all of the other 1500-volt DC infrastructure around the world - or certainly in the developed world - has since been upgraded to the contemporary standard.'' The Napthine government has introduced 1078 extra Metro weekly train trips since it came to office, increasing the rail network's power consumption and carbon emissions. However, both Metro and Dr Morton said rail travel remained a far more environmentally friendly option than cars. ''Even with most of our electricity supplied from brown coal and all the inefficiencies we have with a 1500-volt power supply, we still manage to have very low energy consumption per passenger, especially in peak hour, when our trains are fully loaded,'' Dr Morton said.