Sussex Police said the emergency services responded to a report of a collision, between two cars, just before 11am on Friday (January 9).
The incident – involving a BMW and a Volkswagen – happened on the southbound carriageway, half a mile from the Washington roundabout, police said.
A spokesperson added: “Despite the efforts of paramedics, the driver of the BMW, an 84-year-old man from Worthing was sadly pronounced dead at the scene.
"His passenger, a woman aged 82, was taken to hospital with serious injuries.”
Police confirmed the driver of the Volkswagen, a 54-year-old woman, was also taken to hospital with injuries but has ‘since been discharged’.
Detective Sergeant Ian Foxton said: "Anyone who witnessed the collision or has dashcam footage of it which could help our investigation is asked to email [email protected], quoting Operation Chalkwell.”
The incident was reported in Washington – between Worthing and Horsham.
An air ambulance was pictured at East Brighton Park – near the Royal Sussex County Hospital.
The police confirmed that two cars were involved in the incident – with ‘three people’ affected.
A police statement at 2pm read: “Emergency services have responded to a serious collision on the A24 southbound carriageway, about half a mile from the Washington roundabout.
“Police are appealing for witnesses, and anyone with dashcam footage, to call 101 or email [email protected], quoting Op Chalkwell.”
At 3pm, an AA Traffic News report read: “Road closed and queueing traffic due to crash investigation work on A24 London Road, both ways between A283 Storrington Road (Washington Roundabout) and Washington Bostal. Congestion to Washington Road through Storrington as traffic seeks an alternative.”
The AA reported that the road was initially closed southbound at 11am but was shut both ways around 20 minutes later.
The road has since reopened in both directions.
1. A24 collision
At least one person was airlifted to hospital. An air ambulance has been pictured at East Brighton Park – near the Royal Sussex County Hospital. Photo: Eddie Mitchell
2. A24 collision
Two cars were involved in a collision on the A24 between the A283 (Washington roundabout) and Washington Bostal. Photo: Sussex News and Pictures