Three vans were involved in a pile-up on the M1 northbound just before the Hemel Hempstead junction.
It happened after one of the vehicles hit the central reservation at around 4.30pm yesterday (Thursday).
Two people were taken to Watford General Hospital with minor injuries.
The vans - a white Mercedes Vito, a blue Volkswagen Transporter and a Citroen Relay - were recovered at around 6pm. Traffic was queuing back past the Watford junction on the northbound carriageway.