The global giant behind Metro Trains is celebrating a windfall from Melbourne's rail network, despite the train operator failing to meet performance targets nearly two-thirds of the time.

Metro now gets paid $786 million a year – a 20 per cent increase, or $164 million extra every year, under its current deal with government, compared with its previous contract.

This is despite only 92 per cent of trains arriving on time last year. Trains must arrive more than five minutes late to be categorised as late.

The lucrative contract for MTR Corporation – Metro Trains' Hong Kong parent company – led to the giant listing Melbourne as a key driver of a 14 per cent revenue rise in the first six months of 2018.

MTR runs railways in Hong Kong, Stockholm, London and Beijing and is a major property developer in Hong Kong, highlighting how valuable the deal is to the multinational.