The facts emerging this week that the extensive works on the Tamar Bridge to add two new lanes and strengthen it, have resulted in it sagging by eight inches, are nothing to worry about and were expected. This is according to Kvaerner Cleveland Bridge Ltd, who are the works main contractor.

They say motorists have nothing to fear and that so far the bridge has only moved to where they thought it would.

Confirming it is perfectly safe, they say that at each stage of the strengthening works presently undertaken the construction team have been carefully working out how much they expected the bridge to move, and that so far all their calculations have been correct.

The widening process, during which a cantilever is being added to each side to add the two new lanes, will add a further 4,300 tonnes to the bridge which already weighs in at around 4,000 tonnes, but engineers say the sagging will be reduced and the roadway's natural hump in the middle returned when 16 locked-coil cables, each loaded with 500 tonnes of weight, are fastened to the tops of the two main towers. There will be eight on either side to pull the central deck up again and there will also be an extra two cables underneath the road attached to either end which will strengthen and assist the process.

It was ascertained in March last year that the central deck of roadway had already sunk by a foot after 40 years of use, as the suspension cable had stretched and sagged to take the strain, a natural process.

But the further sinking of eight inches due to the added 300 tonnes of scaffolding and 400 tonnes of extra strengthening steel work has meant that the extra cables are required.

Although thousands of tonnes of weight are being added, they will be compensated for when the traffic eventually diverts on to the cantilevers.

At this time the present concrete deck will be lifted and replaced with 2,000 tonnes of orthotropic steel, which will result in the bridge only weighing an extra 700 tonnes when all the works are completed.

This is also crucial not only for the sagging dilemma but because the bridge was built on the suspension principle and everything is about counter balance.

Contracts manager for Cleveland Mr Alan Platt said that the number one priority is to keep the bridge open.

'That is only possible if we put public safety first and the safety of our people working on it before anything else,' he said.

The works, costing £31-million and presently behind schedule by a month, are set to speed up once the new cables are in place and the cantilever construction can begin again.

It is hoped the final phases will be complete by November 2001.