There are currently delays on the M1 northbound between junctions 5 and 6 due to a car overturning this morning.
At 2.37am Hertfordshire Constbaulary was called to the scene, which is near Watford Junction.
The driver was trapped in the car, a grey Volkswagen Passat, so the fire and ambulance services were also called and the carriageway, between junction 6 and junction 6A was closed.
Giles Cooper, spokesman for Hertfordshire Constabulary, said: "The man was freed and taken to St Mary's Hospital in Paddington with a serious injury."
The vehicle was recovered and the road reopened at around 6.50am.
The delays are up to 15 minutes as a result of congestion.
The investigation into the collision continues and anyone who witnessed what happened is asked to contact Hertfordshire Constabulary via 101, quoting reference ISR 59 of November 27.
Here is a Traffic England map showing the area affected - updated at 7.42am.
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