Officers were called to Stephenson Way at 7.22pm by the fire service to reports a silver Peugeot 307 was on fire.
Sergeant Karl McDermott from the Bedfordshire, Cambridgeshire and Hertfordshire Road Policing Unit said: “It is believed the car had collided with a barrier on the M1 northbound around junction 4 at 7.10pm this evening and then travelled to Stephenson Way where it caught fire.
“I would appeal to anyone who saw the car travelling on the M1, saw the collision or saw the car being driven to Stephenson Way to please contact police with information.”
The driver, a 30 year old man, suffered severe burns and was taken to Watford General Hospital initially but has since been transferred to Chelsea and Westminster Hospital.
The video shows police on the closed carriageway, and ambulance rushing to hospital with a Police escort and sirens blaring.
Drivers are unable to turn down from the M1 / A41 Flyover down towards Watford Town.
Several police vehicles - Police investigation is ongoing and could take til early hours of the morning
#M1 is closed northbound between J1 and J5 due to a serious incident.
A "fatal accident" has shut part of the M1, creating traffic chaos for weekend motorists and thousands of fans departing England's match against Scotland at Wembley.
Highways England confirmed the M1 is closed northbound between Junction 1 in Brent Cross in London and Junction 5 in Watford.
It said: "If you're in trapped traffic on M1 closure btwn J1 and J5. We're hoping to get you released soon. HertsPolice serious incident ongoing."
On its website it said normal traffic conditions are expected between 12:30am and 12:45am.
Wembley Stadium's official Twitter account warned the 87,000 fans who attended the match that the M1 northbound was closed.
It said: "IMPORTANT: M1 northbound is closed due to an accident.
"Please head toward Hanger Lane & use the A40 & M40 to the M25& divert from there."
See link for diversion. http://ow.ly/Cyrv3065RhC