Forth Estuary Transport Authority (FETA) began to be concerned over the structural wear of the bridge in the early years of the 21st century.
The planned theoretical capacity for the bridge (30,000 vehicles per day in each direction) was routinely exceeded as traffic levels outstripped predictions.
The Scottish Government stated in 2006 that 60,000 vehicles travelled on more than half the days in a year.
This raised concerns about the lifespan of the bridge, originally planned at 120 years.

In 2003, an inspection programme was launched (costing £1.2 million) to assess the condition of the main suspension cables after corrosion was discovered in a number of older bridges in the United States of a similar design and size.
The study was completed two years later and reported that the main cables had suffered an 8%–10% loss of strength.
This weakening was projected to accelerate, with traffic restrictions to limit loading required in 2014 in the worst-case scenario, followed by full closure by 2020.

An acoustic monitoring system was commissioned in August 2006, using listening devices to monitor any further strands snapping and pinpoint their location within the main cables.
In January 2006, the Scottish Executive completed a third-party audit on the bridge which concluded that FETA had performed the initial internal inspection and cable strength calculation in accordance with accepted practice.
The report suggested that traffic restrictions could be required by 2013.

Several actions were taken to increase the bridge's lifespan.
These included a dehumidification programme that slowed the rate of corrosion in the main cables by keeping air in the voids between the main cables' strands below 40% humidity.
Engineering consultants Faber Maunsell began work on the project in 2006; it took two and a half years to complete at a cost of £7.8 million.
As part of the works, some of the corroded cable strands were spliced.

The southbound carriageway of the bridge was closed on 1 December 2015, with all traffic using a single lane each way on the northbound carriageway after steelwork defects had been discovered during routine inspections, and traffic was restricted to 7.5 tonnes or less (public service vehicles excepted).
On 4 December, the bridge was fully closed when further structural faults were found.
It was initially not expected to reopen until January 2016, and Transport Scotland began work to lay on extra trains and buses and considered whether to reintroduce a ferry service to mitigate the impact on travellers.

On 23 December, the bridge was reopened for all traffic except heavy goods vehicles (HGVs).
On 4 February, it was announced this had been pushed back to March, due to further problems with the truss end link pins in the southern towers, which required additional remedial work.
However, a limited number of HGVs were allowed to cross, in a northbound direction only, between 11 pm and 4 am each night.
On 20 February 2016, the bridge was fully reopened.
Forth Estuary Transport Authority (FETA) began to be concerned over the structural wear of the bridge in the early years of the 21st century. The planned theoretical capacity for the bridge (30,000 vehicles per day in each direction) was routinely exceeded as traffic levels outstripped predictions. The Scottish Government stated in 2006 that 60,000 vehicles travelled on more than half the days in a year. This raised concerns about the lifespan of the bridge, originally planned at 120 years.
In 2003, an inspection programme was launched (costing £1.2 million) to assess the condition of the main suspension cables after corrosion was discovered in a number of older bridges in the United States of a similar design and size. The study was completed two years later and reported that the main cables had suffered an 8%–10% loss of strength. This weakening was projected to accelerate, with traffic restrictions to limit loading required in 2014 in the worst-case scenario, followed by full closure by 2020.
An acoustic monitoring system was commissioned in August 2006, using listening devices to monitor any further strands snapping and pinpoint their location within the main cables. In January 2006, the Scottish Executive completed a third-party audit on the bridge which concluded that FETA had performed the initial internal inspection and cable strength calculation in accordance with accepted practice. The report suggested that traffic restrictions could be required by 2013.
Several actions were taken to increase the bridge's lifespan. These included a dehumidification programme that slowed the rate of corrosion in the main cables by keeping air in the voids between the main cables' strands below 40% humidity. Engineering consultants Faber Maunsell began work on the project in 2006; it took two and a half years to complete at a cost of £7.8 million. As part of the works, some of the corroded cable strands were spliced.
The southbound carriageway of the bridge was closed on 1 December 2015, with all traffic using a single lane each way on the northbound carriageway after steelwork defects had been discovered during routine inspections, and traffic was restricted to 7.5 tonnes or less (public service vehicles excepted). On 4 December, the bridge was fully closed when further structural faults were found. It was initially not expected to reopen until January 2016, and Transport Scotland began work to lay on extra trains and buses and considered whether to reintroduce a ferry service to mitigate the impact on travellers.
On 23 December, the bridge was reopened for all traffic except heavy goods vehicles (HGVs). On 4 February, it was announced this had been pushed back to March, due to further problems with the truss end link pins in the southern towers, which required additional remedial work. However, a limited number of HGVs were allowed to cross, in a northbound direction only, between 11 pm and 4 am each night. On 20 February 2016, the bridge was fully reopened.
Forth Road Bridge