Warning signs to let drivers know of stranded vehicles were unable to be set by National Highways control room staff for seven hours.
The outage on Wednesday from 2.30pm hit nearly three-quarters of all-lane running (ALR) smart motorways, including large sections of the M1 in the north, the M3, M4, M5, M6, M56 and M62.
Hard shoulders have been removed from ALR motorways and turned into a live-lane of traffic to increase capacity. If a vehicle breaks down – running the risk of being hit from behind – drivers are supposed to be alerted on overhead gantries which display warning signs and lane closures.
Edmund King, president of the AA, said: “If we can’t rely on the technology, drivers are just sitting ducks if they break down – and we can’t have a system like that.”
Greg Smith, who sits on the Commons transport committee, said yesterday the failure meant “motorists were dicing with death or were sitting ducks if they broke down”.
Prime Minister Rishi Sunak pledged to axe ALR motorways during the Tory leadership campaign.
National Highways’ Andrew Page-Dove apologised, saying the “planned” outage “was in response to unexpected issues”.
He added: “We took additional measures to limit any impact…including extra traffic officer patrols and virtual CCTV patrols.”