The Highways Agency was advised to upgrade its fog warning system 18 months before a fatal pile-up on the M5 claimed seven lives, it has been claimed.
An engineering consultancy, looking at potential systems that could be introduced, recommended an automated scheme to warn motorists in Somerset of the dangers of fog.
The BBC said the report by Balfour Beatty-Mott McDonald stated that the motorway suffered significant fog problems, and the area around the crash site was rated as high risk.
It also stated an automated system triggered by fog would be cost-effective and that much of the infrastructure was already in place.
Automated systems are already used on the M25 and the technology has been installed on a number of motorways in the North West.
But the current system on the M5 is manually activated if fog is seen on the road - either via CCTV or from police calling in to the Highways Agency control centre.
The Highways Agency confirmed it had received the report into warning systems on the M5 in April last year, but said it was not commissioned to look at a specific hazard and was part of a range of reports on potential technology information systems that could be introduced on Highways Agency roads in the South West - if appraisals showed they were good value for money and funding became available.
It added that technology funding in the current financial year was allocated to the installation of weather stations, which help inform decisions on road salt treatments against snow and ice and information provided to the public.
"We cannot comment on the possible causes of the collision on the M5 while police investigations are taking place," a spokesman said.
"Fog warning messages can and are displayed on the M5 motorway, through existing signs and signals. Messages are set if fog is reported and confirmed to be present."