A 59-year-old man was airlifted to hospital with serious injuries after a crash involving two lorries.
The incident happened near to the entry slip road from Junction 8 for Hemel Hempstead and the A414 at around 1.50pm on October 12.
Police said a white Mercedes heavy goods vehicle collided with another white Renault lorry from behind on the M1 southbound.
The 59-year-old man driving the Renault was trapped and Fire and Rescue had to free him.
He was then airlifted to the Royal London Hospital with serious injuries.
A 48-year-old man in the Mercedes suffered minor injuries but did not need to go to hospital.
The northbound carriageway was closed to allow the air ambulance to land, and the southbound carriageway was also closed and fully reopened at around 5.30pm.
Anyone who saw what happened should call PC James Lodge from the Bedfordshire, Cambridgeshire and Hertfordshire Road Policing Unit by calling the non-emergency number 101, quoting ISR 407 of October 12.
Or report information online at https://www.herts.police.uk/Report
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