Three people have been taken to hospital after a two-car smash on the M1.
The accident, which happened at around 1.15pm on Wednesday, involved a silver Citroen Saxo and a silver Vauxhall Zafira.
East of England Ambulance Service spokesman Gary Sanderson said: “A woman and a young boy who were in one car sustained the following injuries - the woman had injuries to her leg and the boy had minor injuries.
“The woman in the other car who was trapped sustained injuries to her abdomen, chest and pelvis.
“Our crews worked very closely with the London HEMS team and the Herts Fire and Rescue Service to treat, stabilise and immobilise the casualties prior to them all being conveyed to hospital.”
The stretch of motorway between J7 and J6a was re-opened just before 4.30pm.