ITV Meridian can reveal safety warning signs on the new M3 smart motorway in Hampshire and Surrey have suffered thousands of faults since the scheme was finished two years ago.
They range from screens not working to red and amber flashing lights failing and warning messages not displaying.
Highways England insists the scheme is safe and many faults are only for a few seconds, but motoring groups say it raises serious safety concerns.
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With the hard shoulder removed, drivers rely on these warning signs on smart motorways to tell them if there's a hazard or breakdown ahead.
However on the M3, the signs have suffered some form of failure on thousands of occasions in just two years.
The data for every single fault was analysed by the Head of Roads Policy as the AA. He discovered one failure took 139 days to repair.
This gantry that bleeds from the M3 onto the M25 is one of the most affected.
- Jack Cousens, The AA
Smart Motorways are currently being constructed on parts of the M27, M23 and the M4.
Highways England have long talked-up the smart motorway technology that detects breakdowns and puts up the warning signs.
The problem is the reliability of the signs may not be as smart as they would hope for.