The budget brought little for the ACT in specific infrastructure funding, but the interest in fast rail could revive long-held hopes for a link to Sydney.

Three business cases for fast-rail connections between "big cities and nearby regional centres" will be funded. The commonwealth will spend $20 million paying half the cost of the businesses cases, inviting submissions later this year from state and territory governments and private sector groups interested in partnering to design, build and operate fast rail in key transport corridors.

Whether a Canberra-Sydney link would qualify even to make a case is not clear, with little detail provided. The budget papers point to the need to boost regional centres while taking the pressure off population growth and congestion in the major capital cities.

The budget kicks off construction of the inland Melbourne to Brisbane freight rail link, with an $8.4 billion equity stake in the project - on which the Commonwealth has already spent $890 million in planning and buying land. And it promises $200 million in 2019-20 and more beyond that for rail projects.

The ACT is banking on federal support for its light rail from the city to Woden, and in spruiking the project Chief Minister Andrew Barr is making the most of Prime Minister Malcolm Turnbull's evident enthusiasm for trains.

Canberra's national institutions will welcome upgrades funded in the budget.

The government has directed $5 million to a "first pass" business case to look at options for new exhibition space at the War Memorial. The space would be dedicated to recent conflicts, including an Afghanistan peacekeeping exhibition, and "a comprehensive collection of wartime objects".

The National Capital Authority gets extra funding to maintain commonwealth assets, but the amount is redacted as commercial in confidence.

At Old Parliament House, $13.6 million goes to lighting, plumbing and "habitable office space".

The National Film and Sound Archive will get $3.9 million for work including temperature-control for collections.

The National Museum gets $8.9 million to establish shared corporate and businesses services across the "collecting institutions".

Operations funding for the national institutions shows an extra $2 million in funding for the museum (to $43.4 million), $1.4 million for Old Parliament House (to $15.8 million), and $1.7 million for the library (to $61.9 million). Funding is stable for the portrait gallery, at $11.2 million, and down $300,000 for the art gallery, to $47.8 million. Staffing is stable across the national institutions.