A woman in her 80s was taken to Watford General Hospital for minor neck injuries after a two-car crash on the M1 on Saturday evening.
The inside lane on the southbound road between junctions 7 and 6a was closed around 6pm while two silver-coloured cars, a Vauxhall Meriva and Ford Focus, were recovered.
Two ambulances, a rapid response vehicle and a paramedic attended. Another person was treated for non-serious injuries.