The Queensferry Crossing is to partially close overnight this weekend - as work takes place on new sensors to monitor the bridge's structural health.
Traffic will be diverted over the Forth Road Bridge during the work.
The northbound carriageway closure will take place between 10pm on Saturday and 2am on Sunday. The southbound closure will follow after that and all traffic management will be removed by 6am on Sunday.
A Transport Scotland spokesperson said: "This test will see a number trucks of known weight driven over the Queensferry Crossing in both directions. Data recorded by the sensors from this exercise will allow us to implement final calibrations to this equipment where necessary.
"In order for this testing to be carried out we’ll have to restrict traffic on one carriageway at a time. Discussions between Transport Scotland, FCBC and the Trunk Road Operating Company have concluded that the simplest option with least disruption to road users is to use the Forth Road Bridge as a diversion route.
"As this work is being undertaken over a single night, we don’t anticipate that it will cause any congestion problems."