The state Coalition has tied its political fortunes to a budget with record infrastructure spending that will accelerate plans for the long-awaited metro rail tunnel and include more than $1 billion for level crossing upgrades.

At the centre of the infrastructure pitch - expected to involve more than $20 billion worth of major projects - will be plans for a realigned metro rail project to dramatically boost the capacity of the network by adding a dedicated line connecting to the City Loop from the east to the city.

A key claim will be that three years of prudent budget management have enabled the government to unleash a level of infrastructure spending rivalling the Kennett years, despite economic headwinds.

State Treasury is expected to predict strengthening employment, solid economic growth and strong surpluses across the four-year budget period.

The budget will also include funding for a rail link to the airport, a second stage of the East West Link, an upgrade to the Cranbourne/Pakenham rail corridor and level crossing upgrades.