All lanes are now reopened following a multi-vehicle crash on the M1 southbound between Junction 9 Harpenden and Junction 8 Hemel Hempstead.
Three lanes were closed earlier this morning as emergency services dealt with the incident.
A Highways England spokesman: "We've moved all vehicles to the hard shoulder and re-opened lane 1.
"#M1 southbound between J9 (#Harpenden) and J8 (#HemelHempstead). Delays should begin to ease. Safe onwards journey."