The ARA says estimates of $66 million per kilometre would make a Canberra light rail network the most expensive in the world.

The peak rail industry group says Darwin's Lord Mayor, Katrina Fong Lim is pushing for light rail in the Northern Territory with costs of $17 million per kilometre.

The NSW government recently costed its six-kilometre inner-west Sydney light rail expansion at $176 million, or $29 million per kilometre, less than half the ACT government's estimate.

The ARA says just like the ACT, land is available in the NT to accommodate light rail which helps keep project costs down. However, the ACT has still priced the potential 13 km light rail line at $66 million per kilometre, more than triple the estimates for Darwin.

ARA chief executive Bryan Nye says light rail is firmly back on the agenda in every state except that of Australia's capital.

"The Northern Territory mayor's announcement means every state and territory in Australia except the ACT has seen the light when it comes to light rail." says Mr Nye.

"One tram line can move 10,000 passengers an hour, while the same space dedicated to road moves only 800 cars or 140 bus services."

The ACT Government estimates of $600 - $860 million for a light rail line between Gungahlin and Civic clearly favours continuing to only provide bus public transport in the Capital City.

"Our local Government should be learning from the experiences in other jurisdictions," says Mr Nye.