But personal circumstances meant he then opted for the train and Mr Webber said the subsequent comparison of time and costs surprised him.

According to an Institute for Sustainable Transport Report released last week - Oil Vulnerability in Melbourne - Melton residents could be spending up 10per cent of their income on petrol if predictions of massive petrol price increases prove correct.

Mr Webber said his hybrid used just over 5 litres per 100 kilometres.

He spends less than $20 a week on commuting to the city from Melton, but costs can be doubled, if not tripled, for those who drive a large car such as a Holden Commodore, which typically uses about 11 litres of petrol per 100 kilometres. Add $13 a day for parking, and about $11 a day for the train on a monthly ticket starts to look more attractive. Mr Webber said he could spend up to three hours a day in his car to and from the city, but doorstep to doorstep by pubic transport saves him about 40 minutes a day - provided trains run on time.

The report compares how much we earn, how far we travel by car and fuel efficiency based on petrol price rise predictions by the CSIRO, of between $2 and $8 a litre by 2018.

Report author and Institute for Sensible Transport director Elliot Fishman says some outer suburbs with low incomes and high car reliance will be "unviable" without a major rethink in transport and urban planning.

Mr Fishman says an orbital public transport system is needed because employment patterns show fewer people work in the city but connectivity between outer suburbs is poor.

Government planners needed to consider creating employment closer to where people live if outer suburbs were to survive the impact of high petrol prices, he said.