Exclusive: Severn Bridge weight limits 'unenforceable'

National Highways failed to renew the traffic order for a weight restriction on the M48 Severn Bridge when it expired three years ago and has since operated the essential safety measure without statutory authorisation.

The Severn Bridge opened in 1966 and previously carried the M4 over the estuary. However, following the opening of a second crossing known as the Prince of Wales Bridge in 1996, the original structure was redesignated the M48. Both bridges carry both England-bound and Wales-bound traffic.

In 2006, weight restrictions were placed on the original bridge after corrosion was found in the cables. A dehumidification system was installed and operating by mid-2008, and by early 2009 this had reduced the relative humidity within the cables below 40%, and therefore below a level at which the steel wires will corrode.

However, National Highways said the corrosion that had already occurred meant that mitigation measures were still needed, including limiting 7.5-tonne vehicles to lane 1, an acoustic monitoring system and cable inspections on a 5 to 6-year basis.

In 2017 ‘The M48 Motorway (Severn Bridge Weight) (Temporary Restriction of Traffic) Order’, which cited ‘the likelihood of danger to the public, or of serious damage to the road’, imposed a 7.5 tonne restriction on lane 2 in both directions.

While the restriction is still in place, the statutory order expired in March 2019. National Highways has said it is currently 'pursuing the statutory processes' to instigate a new weight restriction to mitigate the ‘rare risk’ of having four lanes of HGVs on the bridge.

Chris Pope, project manager for National Highways’ Severn Bridges team, said: ‘A 2017 TTRO, put in place on the M48 Severn Bridge ahead of the operation to remove the tolls from both Severn bridges, expired in March 2019. Since that time, despite showing red circled signs, the M48 bridge has operated with an unenforceable weight restriction.

‘In that time, we are not aware of any prosecutions, and we are currently pursuing the statutory processes to instigate a new order to make the weight restrictions enforceable. The new order is expected to become active in the very near future.’

National Highways said that even with the corrosion, the bridge is ‘more than capable’ of bearing the load of two lanes of nose-to-tail heavy goods vehicles. It said abnormal and heavy loads are routed via the M4 over the Prince of Wales Bridge.

Mr Pope said: ‘The Severn Bridge provides a key link supporting the surrounding local economies, we recognise the importance of keeping it safe and open to traffic.

‘We undertake a thorough maintenance programme to protect the bridge and ensure it is fit for purpose and remains operational for the thousands of motorists who use it on a daily basis.’

Mr Pope added that National Highways and contractor Amey had responded to a recent complaint regarding debris on the cycleways and addressed the concerns raised.

National Highways said the cycleways, which run alongside each carriageway, are swept on a fortnightly basis and that the Amey maintenance team has recently acquired a new compact roadsweeper for that work. The cycleways have an engineering weight capacity of 3 tonnes and the new 2.5-tonne sweeper, fitted with a weight limiter, complies with the weight restriction.

Mr Pope said there is no plan to replace the Severn Bridge when it reaches the end of its life.

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