Inside the tunnels hidden in Brisbane's Gateway Bridge

9News has been given access to the tunnels hidden throughout Brisbane's Gateway Bridge's as new technology was installed on the structure.

Transurban maintenance crews use the cavities to traverse the 1.6 kilometre crossing over the Brisbane River.

Transurban's David Counsell told 9News workers need to crawl through parts of the tunnels and must be in good shape to do the job.

"We like to make sure that we can keep our crews in the right physical shape and equip them appropriately so they can do their job safely," he said.

The Bridge was opened in 1986 but it uses new technology to help change speed limits and alter lighting.

Sensors that monitor the health of the bridge have been installed as part of a trial.

"They measure strain, vibration, temperatures and let us know what's going on with the health of the bridge, while we're underneath it," Transurban's Luke Abercrombie said.

The Gateway Bridge is the most eastern crossing of the Brisbane River and carries traffic north and south on the Gateway Motorway.