Crash barrier safety on M6 toll in question

Safety barrier provision along the M6 toll road has been described as "shocking" and "beyond belief" by one experienced highways engineer. He said crash barriers have "lethal potential" if one of the lighting columns on the M6 is struck by a moving vehicle.

The concerns are so great that the official, who wished to remain nameless, has written to the project’s chief highway engineer at Midland Expressway Limited, the toll concession company.

He claimed that around 25km of safety barriers protecting lighting columns in the central reservation of the 60km highway do not meet Highways Agency (HA) standards.

In a copy of the letter, obtained by CJ, the engineer concluded that the CAMBBA consortium – Carillion, Alfred McAlpine, Balfour Beatty and Amec – did not use current HA guidance for safety barrier clearances (IAN 26), which states that the clearance space, the horizontal distance between the rear of the safety fence and the protected obstruction, should be 1,200mm. This replaced the old TD 19/85 standard, which required a clearance distance of only 600mm.

He wrote: "I believe this safety fence does not comply with the HA standards, hence it is defective. As far as the centre reserve safety fencing is concerned, the requirements of an IAN 26 clearance have not been implemented and the clearance from the tensioned corrugated beam (TCB) is less than the distance specified."

He added: "It would appear that no consideration has been given to the revised clearances for safety fences stipulated by IAN 26, despite it being introduced in April 1999 and the contract for the design and build scheme only being awarded 18 months later in September 2000."

He also pointed out that the beam had a "major installation fault" as it was installed with posts spaced at centres of 3.2m.

"At obstructions such as lighting columns it is accepted practice to halve the post spacing to 1.6m centres. The purpose of halving the post spacing is to increase the stiffness of the safety fence and reduce its deflection under impact.

"The zone of half-spacing should start 10m before the obstruction and continue 7.5m beyond it. Unfortunately on the centre reserve, the TCB has posts at half-spacing before the lighting columns, and leaves the fence weakest at its most vulnerable point," he added.

In a final note, the engineer remarked that under British Standard Published Document PD 6634 Part 3, introduced in 1999, a TCB should not have been installed on the motorway as there was insufficient width and that an open box beam barrier should have been used.

A spokeswoman for Midland Expressway Limited said the company was "investigating the points raised".

The company also confirmed it was using TD 19/85, including Amendment No1, and said that standards changed earlier this year, from steel barriers to concrete: "It is worth noting that in January 2005, the HA issued IAN 60/05 This introduced a requirement that centre reserve safety fences on motorways and other busy dual carriageways should henceforth be made of concrete."

CJ contacted CAMBBA, which said: " The CAMBBA consortium has carried out the construction of the central reserve crash barriers on the M6 toll road in accordance with the HA’s specifications, as included in the concession agreement."