THE Liberals have pledged $1.6 billion in infrastructure spending over the next four years, with hundreds of millions of dollars to be funneled into road and bridge upgrades.

Midland Highway works are front and centre of the government's roads cash splash, with $50 million set aside over the next five years.

The government has penned a $33 million promise to reintroduce a direct international shipping service, but there is still no word on who the operator will be.

It has also come good on its $30 million commitment to the second tranche of the state's irrigation rollout, with the outlay to be spread across five years.

The state's ailing rail network will also receive a $97 million injection.

Treasurer Peter Gutwein stopped short of pushing for a forced merger between TasRail and TasPorts, but says the two will be encouraged to foster greater alignment in operations and investments.