A coroner investigating two deaths on the M1 near Watford has warned of more fatalities if a gap in the safety barrier is not filled.

Jacques Howell, area coroner for Hertfordshire, oversaw an inquest into the deaths of 18-year-old Tyler Cox and her father Darren Reilly, 55, who died on 1 April 2024.

Mr Reilly was driving a Range Rover, with his partner and three children as passengers, when he lost control of the vehicle around a mile before the southbound slip road exit at junction five.

According to the coroner, the vehicle left the carriageway through a gap in the safety barrier and crashed into trees. Mr Reilly and Miss Cox died at the scene.

The coroner's report reads: "Along this section of the M1 southbound there are safety barriers to the nearside of the carriageway.

"If a vehicle loses control, the safety barrier is designed to prevent a vehicle from leaving the carriageway, the idea being that a vehicle that has lost control will continue along the safety barrier before coming to a more controlled stop, thereby minimising the risk of serious injury or death to passengers.

"This is particularly important when a high-speed carriageway … is lined with established trees, as is the case here.

"Whilst I heard evidence that, in general, gaps are sometimes inserted into the safety barrier for the purposes of access or due to the presence of other safety measures (e.g. a grassed bank), the witnesses from the roads policing unit could not offer any explanation for why there is a gap in the safety barrier at this location.

"Consequently, I am concerned that there is a gap in the safety barrier at this location, which … gives rise to a risk that future deaths may occur.

"In my opinion, action should be taken to prevent future deaths."

The coroner has given National Highways, the Government agency responsible for managing, maintaining and improving England's motorways and major A roads, until 12 September to provide a response.

A spokesperson for National Highways told the Local Democracy Reporting Service: "Any death on our roads is one too many and our thoughts are with the family and friends of Darren Reilly and Tyler Cox following this tragic incident.

"We will review the coroner's report and respond with the deadline."

After the crash, Miss Cox's family said that she was "deeply missed by all who knew her" and that "her maturity and wisdom was undeniably beyond her years".

Mr Reilly's family said: "He leaves a large void in our family – a void that will never be filled.

"Dad had the biggest personality, the biggest heart and when he was passionate about something, everyone knew."