The Traffic Regulation Order does not restrict HGVs up to 44 tonnes from using the bridge in lane 1 in either direction.

The weight restrictions follow the initial findings of continuing inspections of the main suspension cables. The inspections follow surveys at the Forth Road Bridge in 2004 which revealed some evidence of corrosion inside the cables. Surveys on the Severn Bridge started in April and will continue until early next year.

The M4 Second Severn Crossing is the main route for heavy vehicles travelling to South Wales. On an average weekday about 3,000 HGVs use the M48 Severn Bridge but only around 100 use lane 2. The use by lorries is much lower at weekends.

Highways Agency Route Performance Manager Chris Pope, said: "Today as a precautionary measure we are giving notice that we will implement a Traffic Regulation Order which will introduce a temporary 7.5 tonne weight restriction on lane 2 of the bridge in each direction. The weight restriction will reduce the potential overall weight of traffic on the bridge and will minimise the risk of further deterioration of the cables. We are continuing the investigation of the cables. When testing is complete and all of the investigation results are known we will take the necessary steps to maintain the structure. This will include repair work as appropriate. Any work will be planned so that disruption to road users is kept to a minimum.

"There is no risk to the public and no plans to close the bridge."