Consultants brought in to look at the problem of ice on Severn Bridges have scoured the world for information on similar cable supported bridges, Plaid Cymru AM Chris Franks has learnt.
Chris Franks, who represents South Wales Central, has obtained a copy under the Freedom of Information Act of a report from Mott MacDonald, which was commissioned by the Highways Agency to look at the issue following the closure of the Second Severn Crossing a year ago.
The document, entitled Winter Resilience Report, looked at snow ice incidents which led to closures of bridges in Canada, Norway, Sweden, the United States and Japan.
In its report, Mott MacDonald said: “The review has shown that most bridge authorities have not provided mitigation measures to the snow/ice accretion on cable systems.
“As there have only been two instances of snow/ice accretion which resulted in the Severn Crossing being closed in over 40 years, the economic benefits of providing specific facilities to prevent ice accretion will be very low. But the implication of injury to users would be serious.”
In its conclusion, Mott MacDonald said: “The review has shown that the criteria adopted by the Japanese on the Hakucho Suspension Bridge, would enable a reasonable prediction of snow/ice accretion on the Severn Crossing to trigger the operator to undertake visual patrols.
“It is recommended that discussions are held with Campbell Scientific to ascertain if appropriate software can be developed to allow ice accretion monitoring by the Highways Agency traffic officers service or Severn River Crossing.”
The report says the Hakucho Bridge has been shut twice between 1998 and 2007 due to falling snow on the main towers and cables. Their investigations showed that snow accretion was likely on the bridge when weather conditions were between -1.5C to 1.5C with a wind speed of 8m per second with 90 per cent humidity.
The Highways Agency told Chris Franks that in association with the Met Office, weather conditions that could lead to ice problems had been identified. If such conditions are predicted, the crossings are monitored for any ice build-up and closed prior to ice falling.
Earlier this year the agency told the Plaid AM that 12 claims for compensation had been made following ice falls which closed the two Severn bridges for a total of 54 hours in 2009.
The agency said that the Second Severn Crossing had been closed for a total of 44 hours on three occasions, twice in February 2009 and once in December 2009, due to ice. While the original Severn Bridge was shut twice for a total of 10 hours. Between 30,000 and 40,000 vehicles use the bridge daily.
Chris Franks said: “My concern in raising this issue with the Highways Agency was borne out of concern for the safety of drivers crossing both Severn bridges after the last incident in December 2009.
“It is vital that every measure is taken so that there is an early warning system of potential weather conditions which could lead to a build-up of ice so it can be treated before there is any danger to the public. And if that can’t be done then the bridges must be closed.”
