Lessons must be learned on Forth Bridge closure

Last week a parliament committee published its report into the closure of the Forth Road Bridge.  It concluded that the fracture was not foreseeable.  It was, by design, a narrow inquiry that only sought to focus on the political and budget decision making.  It did not address compensation, the travel arrangements and the wider engineering issues.

I pay compliment to the Minister Derek McKay.  Throughout this episode I admired his approachable manner and his clear interest in finding pragmatic solutions.  He even answered my questions - surely a model for his colleagues to follow. He had two tasks: getting the bridge reopened safely and keeping the traffic moving around temporary routes.

I thought transport officials worked well to devise a transport plan in just a few days after the traditional route for the last 50 years had been disrupted.  But it was clear no preparations had been made for such an eventuality despite the age of the bridge.

The extra train carriages and buses at discounted rates were good initiatives. The use of the priority route for HGVs was effective but should have been opened to a wider group of vehicles at an earlier stage and at off peak periods to all vehicles.

The challenge for the minister was to get the bridge opened on time.  He did that for cars but not HGVs. The closure for everyone was costly but the further delays for HGVs compounded the problem.  I think there is a strong case for a compensation package for businesses in south Queensferry who lost the Christmas trade - which by its nature can never be recovered.  I also think there is a case for support for companies who priced jobs based on the bridge being reopened by the New Year.

It is a fact that the budget for bridge maintenance was cut but I have never believed that any politician or government would reject urgent and critical repairs.

It is also the case that keeping to a minimum the disruption to traffic flows was a factor as much as cost reduction. Major, just in case, repairs could have been incredibly disruptive and costly. Delaying major repairs, by using temporary fixes, until after the new bridge opened was an understandable approach.

The design of the bridge has made it difficult to maintain and inspect so I trust the new bridge will have good maintenance arrangements built in.

With such an ageing structure that was well beyond its capacity - and has been so since 1990 - the probability of failure was high.

The brackets on the truss end links were identified as vulnerable areas and a fix had been designed when the bottom end of the truss end link fractured. Now we know this happened, at least in part, because the pin was not moving.

However, there are a number of questions that remain unanswered.  As I am a biologist rather than an engineer I sought advice from an engineering professor.  We met the bridge engineers for a specialist briefing for which I am grateful to the minister and Transport Scotland.

The big question is why was it not identified that the pin in this area was not moving properly?  The whole area was being considered and I would have thought that as it could not be inspected and because it was not lubricated that this should have been an area that required closer scrutiny.

Why was strain gauge monitoring equipment not used in this area?

There was no lubrication for the bottom pin, when there was for the top pin, why was this not flagged up as a risk?   Would it have been possible to grease remotely?

These are not political matters but matters for the engineering profession to consider.

I have respect for Mark Arndt, Barry Colford, Alistair Andrews and all their predecessors for keeping such a critical piece of infrastructure alive whilst it is under considerable strain.

I hope they and the government agree to further scrutiny from the profession and for the evidence to be made freely available for such an examination.

Despite the fact that I requested a parliamentary inquiry the engineering community must examine this too.  We must learn lessons. That is our duty.

Share this post on social media:

Sign in with Facebook, Twitter or Email.