The exercise, run by City of Launceston council, will test the bridge’s Bauer flood gate system. 

Launceston Mayor Albert van Zetten said motorists could take alternate routes across the Tamar Street Bridge while the exercise was underway.

“We undertake these drills every few years to demonstrate to council staff and emergency services representatives how the Bauer flood gates are installed and set up," Mayor van Zetten said.

“This allows them to experience first-hand what work needs to be undertaken, how the gates are installed, and what equipment is required.”

The exercise means an “appropriate” number of people are familiar with how the system works, if it was needed. 

“The Bauer flood gates comprise a series of rubber-sealed 'stop logs' which are placed between upright posts that are bolted into the road, as opposed to the city's sliding gates which can be rolled across gaps in the levee system and tensioned into place,” Alderman van Zetten said.

“Both types of gates are designed so that they can be set up quickly and without heavy machinery, and while we're able to test the sliding gates without any great impact on the public, the Charles Street Bauer gates do require the closure of the bridge to traffic.”

Alderman van Zetten said it was “very important” to regularly test the equipment to identify any improvements that could be made or any problems the council could encounter. 

The bridge will be closed from 7pm until 9pm on Tuesday night.

“We apologise for any inconvenience to motorists during this time, and ask for people's patience while the exercise is underway,” Alderman van Zetten said. 

The flood gates were used during the 2016 June floods. The gates are expected to be able to perform during a one-in-200-year flood.