The decision to close has been taken after inspections carried out by specialist engineers and following advice and assessment of the fault by independent experts.

A range of options for carrying out the repair work has been considered including running traffic on the bridge while repair work is in progress.

However, even with a restriction in place on HGVs using the FRB, continual running of traffic over the bridge increases the risk of causing extensive secondary damage to the structure.

Further damage to the bridge would require a full closure for a much longer period in order to carry out repairs.

Work is already under way to repair the FRB and this will be done as quickly as possible with a view that it will be reopened to traffic to allow it to be used for the return to work in January.

Additional rail capacity was put on overnight and a full travel plan is being prepared for the duration of the closure.

This will include further additional rail services. All other options are being explored including a dedicated bus corridor with park and ride facilities and passenger ferry services across the Forth.

The Scottish Government Resilience Committee (SGoRR) will continue to meet over the weekend and further updates will be provided and a dedicated webpage for travel information will be created.

Emergency vehicles will still be able to use the FRB in bluelight situations.

Transport minister Derek MacKay said: “The decision to close the Forth Road Bridge is not taken lightly. It is based on the expert opinion of the engineers who operate the bridge day to day and that of independent experts in the field.

“Every effort is being made to open the bridge as quickly as possible but safety is the main priority, however these works are weather dependent given the height and location of the bridge. We are aware of the potential economic impact, for strategic traffic in the east of Scotland and on people living in local communities.

“This is an unprecedented challenge in the maintenance of the Forth Road Bridge. On balance following advice from engineers and independent experts, the full closure is essential for the safety of the travelling public and to prevent further damage to the structure of the bridge.

“The bridge operators Amey have a robust inspection team is in place and these defects are problems that have only occurred in the last number of weeks.

“We are taking every step we can to lessen the impact of this closure. Action now, will mean that any closure is much shorter than it might be if we waited. We continue to work closely with all partners to co-ordinate our efforts to lessen the impact of this closure. Additional bus and rail services are being provided between Fife and Edinburgh. Every effort and resource available is being deployed to repair the damage to the Forth Road Bridge and minimise the disruption to the public.”

Chartered Engineer Mark Arndt, Amey’s account director responsible for the bridge, said: “This is a complex engineering challenge. The component failure is in a difficult to access location and our response is also highly dependent on weather conditions.

“We continue to work around the clock on inspections, assessments and calculations along with the development of designs to effect the necessary repairs, while at the same time mobilising all the resources required to reopen the bridge as soon as is possible.”