It has been claimed that the highways body in charge of the M5, which saw a fatal pile-up two months ago killing seven people, was advised to install new fog warning systems last year.
The BBC said an engineering consultancy recommended in a report that an automated system could be installed to warn motorists on the Somerset motorway of the dangers of fog, 18 months before the large scale crash.
The report by Balfour Beatty-Mott McDonald said the M5 had significant fog problems and rated the area around the fatal site as high risk.
It said upgrading the current fog warning systems would be cost-effective and much of the infrastructure was already being used around the area.
The current system used on the M5 is manually activated when fog is either seen on CCTV or if the police inform the Highways Agency control centre.
The agency said it did receive the report last April but said it was not commissioned to look at certain hazards and it was part of a group of reports looking into technology systems that could be used in the South West if further investigations proved they were viable.
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