Light rail could be back on the agenda for Perth after Malcolm Turnbull's elevation to the prime ministership, a sustainability expert says.

In revealing his Cabinet, Mr Turnbull announced a new Cities and the Built Environment portfolio and said the Government would no longer prioritise roads over public transport.

Curtin University sustainability expert Jemma Green said she believed light rail was now back on the agenda for Perth in the near future.

"I think rail has a much brighter future than before that statement was made," she said.

"The business case for light rail is very compelling and if you compare that against alternatives like road or bus, it is going to be a no-brainer.

"He [Tony Abbott] said the Federal Government would only be funding road projects, and as a result of that, no money was allocated from the Federal Government to anything other than road projects.

"The fact that ideology has been taken out of the evaluation of transport projects and now it will be done on merit basis means light rail has a much bigger chance of happening in Perth sooner."

The State Government announced plans to develop in the MAX light rail system in September 2012, but earlier this year delayed a decision on the investment to 2017.

It then announced an alternative plan to use rapid bus services to battle congestion in the CBD.

Ms Green said rapid bus services were a bandaid solution and she was pleased it seemed Mr Turnbull would consider providing funding assistance to light rail projects.

"The reality is, bus transit doesn't facilitate land development and in the next phase of growth in Perth we need to increase the density of our cities and light rail can facilitate development around it," she said.

"Around the world governments are giving greater emphasis to cities. Cities now compete with one another in the global economy to attract top jobs and top talent.

"The more liveable a city, the more competitive it is and the more likely you are to get companies to set up their head offices here."