Last updated on 24 Oct 2009
This page contains answers to a number of frequently asked questions about the Forth Road Bridge and the bridge authority. Please feel free to get in touch with any questions not covered here.
How many staff are employed at the Forth Road Bridge?
Normally around 70, but this increases during the period April to October when around 10 additional painters are employed on a temporary basis. Staff responsibilities include bridge maintenance, traffic management and administration.
What is the heaviest vehicle that can be carried by the bridge?
The bridge was designed to carry a four-axle, sixteen wheel design vehicle weighing 180 tons. In practice, such vehicles are never used on the roads as special multiple axle trailers are used to transport abnormal loads. The bridge has carried 215 tons spread over 15 axles. All such loads require to be notified for acceptance following analysis.
Does the increase in traffic volumes affect the bridge?
No. The bridge has been substantially strengthened since 1964 to cope with current traffic loading including the new 44 tonne commercial vehicles. Once the bridge is full of vehicles, the maximum load is reached. The loading is not affected by other vehicles in a queue waiting to get on the bridge.
How often is the bridge painted?
It is a commonly held misconception that we are constantly painting the bridge. The different elements of the bridge have varying needs. For example during the summers of 2002 to 2005 the main towers will be overcoated with a modified polyurethane paint providing a further 25 years protection. Painting the underside of the steel deck can take 10 years but the life of the paint system will be 25 years.
How long will the bridge last?
The original design life was 120 years but with proper maintenance the bridge will last longer than that. Within the design life, major components will require to be replaced such as the suspender ropes (replaced after 35 years), expansion joints and bearings. Surfacing on the deck needs to be replaced more frequently, especially as traffic levels grow.
Some doubt has recently emerged over the lifespan of the bridge following the discovery of corrosion in the main suspension cables, but FETA is optimistic that the dehumidification system currently being installed will prevent further deterioration.
How much does the bridge move?
The bridge is very flexible. If the wind blows at 110 miles per hour, the centre point of the bridge will have moved about 7m in the direction of the wind. If the temperature rises by 20 degrees centigrade the centre point will drop by 1m. This flexibility is quite normal in long span suspension bridges and is hardly noticed by drivers.
Has the original debt been repaid?
The original cost of the bridge was £19.5 million of which £14 million was a Government loan. The final payment on the loan was made in December 1993.
Why the need for minor roadworks?
The Forth Road Bridge is over 40 years old and is now carrying more load than it was designed for. In order to keep the bridge available to you we need to carry out regular maintenance of a routine nature. This work can include weld repairs to the steelwork below the road level and repairs to the road surfacing and expansion joints. Where practical these “routine” repairs are undertaken overnight when the traffic volume is low and delays are minimised. These works continue throughout the year.
Why the need for major roadworks?
In addition to routine maintenance, major works are also required some of which by their very nature must be carried out during daylight hours. Where practical these major works are restricted to weekends and kept to a minimum. Such works can be sensitive to weather conditions and other operational difficulties and hence subject to last minute change. Significant changes to planned works will be notified as soon as possible.
- RT @BBCScotlandNews: IN PICTURES: Your reflections on the #ForthBridge as it marks its 125th anniversary http://t.co/knPt4KxfK1 http://t.co…