KING CONE is back just when motorists thought it was safe to get back on the A19.

With the railway industry it was always the wrong kind of leaves on the track.

With the A19 Tees Viaduct, at Middlesbrough, Teesside, the problem is de-icing salt put on the roads every winter.

The bridge, built at a cost of £17m, 25 years ago to take the A19 over the River Tees, has now cost more than £25m in repairs - almost £1m a year.

There is no foreseeable end to the spending, although the problem is declining, it emerged last night.

Thirty one chloride-damaged joints in the bridge are being replaced at a cost of £250,000. Night-time lane closures have been introduced to keep traffic disruption to a minimum.

Keith Polson, customer service manager for Autolink, the business consortium which maintains the A19, said: "The whole contract, which is in two phases, will last for about seven weeks in all.

"The first phase of the work, which involves the closures of the A19 over the A19/A1046 Portrack Interchange, is due to end on August 9.

"That work has started, and so far the closures have not caused any major problems. When the closure is in place, traffic is being diverted off and on to the A19 slip roads at Portrack. All the diversion signs are clearly signed.

"Phase two of the work, which covers slip road closures on the A19/A66 Stockton Road Interchange, will last for about two weeks and this phase will be carried out in November. Again, all diversion routes will be clearly signed."

A spokesman for the Government's Highways Agency said: "It is chloride, which is part of the de-icing material in the salt put down on the roads in the winter. It was running into the concrete.

"Down at Spaghetti Junction (near Birmingham, in the West Midlands) they have similar problems. It is a particular problem with this type of concrete construction.

"The bridge has a design life of 120 years. It was built to design specifications relative to the time of construction. Since then standards of bridge design have moved on."