Overview
- Both southbound lanes between Junction 3 (St Albans/Hatfield) and Junction 1 (M25) were closed overnight after a serious collision.
- One southbound lane has reopened, and the other remains shut for safety barrier repairs.
- Hertfordshire Police are leading the response and have confirmed a full investigation will not be required.
- National Highways fully closed the carriageway overnight to complete collision investigation, vehicle recovery and safety checks.
- Drivers are directed to follow the hollow-circle diversion via the A414, A1081 and the M25.