The rollout of smart motorways should be suspended due to safety concerns, according to MPs.

A report by the Commons’ Transport Select Committee (TSC) said there is not enough safety and economic data to justify continuing with the project.

It described the Government’s decision in March 2020 that all future smart motorways would be all-lane-running versions – where the hard shoulder is used as a permanent live traffic lane – as “premature”.

Concerns have been raised following fatal incidents involving broken-down vehicles being hit from behind.

Demonstrators protesting against smart motorways marched with coffins to the Houses of Parliament on Monday.

The TSC urged ministers to “consider alternative options for enhancing capacity” on motorways.

The committee’s report said: “The Government and National Highways should pause the rollout of new all-lane running schemes until five years of safety and economic data is available for every all-lane running scheme introduced before 2020 and the implementation of the safety improvements in the Government’s action plan has been independently evaluated.”

Controlled smart motorways – which have a permanent hard shoulder and use technology to regulate the speed and flow of traffic – have the “lowest casualty rates” of all roads across motorways and major A roads in England, the report noted.

It called for the Department for Transport to “revisit the case” for installing them instead of all-lane running motorways.

Measures included in an 18-point action plan to improve smart motorway safety published in March 2020 – such as retrofitting technology to identify stopped vehicles – fail to “fully address the risks associated with the removal of the hard shoulder”, the MPs warned.

Relatives of those killed on smart motorways have called for the hard shoulder to be permanently reinstalled on the roads.

But the committee was “not convinced” that such a policy would boost safety.

It concluded: “The evidence suggests that doing so could put more drivers and passengers at risk of death and serious injury.

“The Government is right to focus on upgrading the safety of all-lane running motorways.”

The report recommended that emergency refuge areas are retrofitted to existing all-lane running motorways to make them 0.75 miles apart “where physically possible”, and a maximum of one mile apart.

Tory MP Huw Merriman, who chairs the committee, said: “Looking at the available evidence, smart motorways do appear to be safer than conventional motorways even once the hard shoulder is removed.

“However, this evidence is also open to question. Only 29 miles of these all-lane running smart motorways have operated for over five years.

“It therefore feels too soon, and uncertain, to use this as an evidence base to remove the hard shoulder from swathes of our motorway network.”

Claire Mercer, whose husband, Jason Mercer, died on a smart motorway stretch of the M1 in June 2019, gave a mixed response to the report.

Asked about the conclusions, she told the PA news agency, “I don’t think they’re strong enough”.

But she welcomed the recommendation for the rollout of smart motorways to be paused, as “that will give us more time to get into the High Court and get these banned anyway”.

Conservative MP Sir Mike Penning, who claims he was misled when he supported the rollout of smart motorways in his role as roads minister from 2010-2012, said the TSC’s findings were “another significant step in the fight to improve safety on these motorways”.

The RAC’s head of roads policy, Nicholas Lyes, said: “We feel a huge question mark remains over whether it’s right that yet more money is spent on rolling out further all-lane-running smart motorways when there are clearly viable alternatives available.”

A Department for Transport spokesperson said: “We welcome the Transport Committee’s scrutiny and will now consider its recommendations in detail, providing a formal response in due course. This is a serious piece of work which we will engage with closely in the months ahead.

“We’re pleased that the TSC recognises that reinstating the hard shoulder on all all-lane running motorways could put more drivers and passengers at risk of death and serious injury and that we’re right to focus on upgrading their safety, as the Secretary of State committed to doing when he became Transport Secretary.

“We recognise that improvements have not always been made as quickly as they could have been in the past, but as the committee has set out, the Transport Secretary is absolutely committed to making smart motorways as safe as possible, including committing £500 million on upgrades and the faster rollout of Stopped Vehicle Detection.”

Smart motorways were first introduced in England in 2014 as a cheaper way of increasing capacity compared with widening carriageways.

There are about 375 miles of smart motorway in England, including 235 miles without a hard shoulder.

An additional 300 miles are scheduled to be opened by 2025.