A sweeping four-lane bridge across Hobart's Derwent River will cost $535 million and represent Tasmania's most significant transport infrastructure project in more than half a century, the state government says.

The city’s northern Bridgewater Bridge has long been marked for replacement and state infrastructure minister Rene Hidding unveiled the plans, with construction set to start in 2019-20. “This will be the most important single transport infrastructure project in the state since (Hobart’s main) Tasman Bridge was built in the 1960s,”…