Safety first on bridge

STEPS are being taken to ensure that vehicles are not blown over again on the Forth Road Bridge.

After two vehicles were blown over on the bridge in 2008 forcing major traffic problems, the Forth Estuary Transport Authority, which maintains the facility, is looking at methods to install wind shielding on the bridge.

A working group was set up and feasibility studies carried out as what are the best options to minimise the threat of high winds.

They have since found two methods of localised wind shielding. One is similar to what is used on the Severn Bridge using panels of varying height, from 5.25 metres to 1.75 metres, along a 31 metres stretch at either tower leg. This method has proved successful but is visually intrusive.

The other method is similar with all the panels at 5.25 metres in height but more spaced out having less visual impact. The second option is also lighter to construct, can be carried out in-house and would not see the need carriageway closures. The cost of the second option is also less expensive at £1,625,000.

If a decision is made to install shielding, it would be in 2012/13 at the earliest.

FETA has also looked at the possible need to strengthen and protect the main towers in case of a collision with an HGV. While there is a low probability of occurrence, it has been identified as one of the top ten risks which could force the risk of long term closure of the bridge.

But to carry out this procedure, there are a number of challenges to overcome, namely that the barriers would be sited 1.6 metres above the carriageway for a length of 45 metres to each tower leg. This would present problems as the bridge deck and truss would need to widened and strengthened. It also would cost in the region of £6million to install.

Barry Colford, chief engineer and bridgemaster said: “Absolute safety is impossible to achieve and a balance has to be struck between risk and cost. Spending finite resources on one risk means less protection elsewhere.”