Infrastructure Victoria has called for a congestion tax in Melbourne's city centre.

The authority says just a five per cent reduction in CBD traffic would improve congestion as much as school holidays do.

Its 134-page draft strategy for the future includes some major projects – such as North East Link and a new airport rail line – but also focuses on policies and reforms aimed at getting the most out of existing infrastructure.

These include harvesting stormwater, turning vacant land into urban forests, transforming state schools into community facilities, and “a comprehensive transport pricing regime”.

“The challenges we face over the next 30 years cannot be solved just by building new things so we have looked at ways to manage demand and better utilise existing infrastructure,” chief executive Michel Masson said.

The recommendations are broadly in line with the views of a lot of economists, who argue that making driving in the city more expensive is the most effective and direct way to cut traffic.