A coroner has raised fresh concerns over the safety of smart motorways after a teenager died when the broken-down vehicle he was in was hit by a lorry.

Smart motorways often mean hard shoulders are used as running lanes to increase capacity and reduce congestion.

Highways England had to shelve plans to turn a section of the A1(M) - junction 6 for Welwyn to Junction 8 for Stevenage - into a smart motorway by 2022 until 2025 to concentrate on making existing smart motorways safer, after a government review last year led to an 18-point safety improvement plan.

Transport secretary and Welwyn Hatfield MP Grant Shapps said then: "There is more we can do to raise the bar on smart motorway safety."

Stevenage Borough Council's leader Sharon Taylor opposes the A1(M) plan as unsafe, but the town's MP, Stephen McPartland, says it will stop "huge tailbacks putting a massive chokehold on the economic potential of Hertfordshire".

Bedfordshire coroner Tom Stoate has now written to Highways England after concluding an inquest into the death of 19-year-old Zahid Ahmed, killed in 2019 on the smart motorway at the M1 South Junction 11a when the car he was a passenger in broke down where there was no hard shoulder operating.

Zahid suffered fatal injuries when a lorry hit the stationary car.

Mr Stoate writes: "Evidence revealed matters giving rise to concern. There is a risk future deaths will occur unless action is taken.

"A detective constable from the Bedfordshire Police Serious Collision Investigation Unit said: 'The absence of a hard shoulder contributed to the collision. Had the car been able to stop in a location other than a live lane, the HGV would not have driven into the back of it.'

"The car suffered a mechanical defect which caused it to lose power. It is not clear where it could have pulled to a halt in a safe place, given there was no hard shoulder and all lanes were live.

"Action should be taken to prevent future deaths and I believe you have the power to take such action."

The Transport Committee, which scrutinises the Department for Transport, has also launched an inquiry into the safety of smart motorways, and Highways England has begun a televised safety campaign.