The M1 was closed for nearly eight hours between junction 5 in Watford and junction 1 in Cricklewood, yesterday (July 9).
Emergency services were called to the scene at 6.52pm and a man was taken to hospital to be treated for his “serious” injuries.
The driver, another man in his 50s, was arrested at the scene on suspicion of causing serious injury by careless driving and remains in police custody.
During the closure, the M1 was shut southbound, causing severe delays in the area.
Frustrated motorists were stranded into the early hours of the morning, with one taking to social media to write: “There’s thousands of people out of their cars and a number of people running across to the other side of the motorway to pee and catch lifts.”
Police have asked for witnesses to get in touch by contacting the force online or by calling 101 and quoting ISR 663 of 9 July.
