A 32-year-old Bargoed man has been attested on suspicion of manslaughter after a fatal crash on the M4 near Newport.
The crash, between a lorry and a car, happened on the westbound carriageway at junction 25 (Caerleon) at 11.10pm on Wednesday.
A 77-year-old woman, from the Devon area, was taken to the Royal Gwent Hospital in Newport where she later died.
Specialist officers are supporting her family at this time.
The M4 was closed between junction 24 at Coldra and junction 26 until 8am today (Thursday). Traffic was diverted via the A48 southern distributor road until accident investigation work was completed.
Gwent Police has said that because the lorry involved in the crash was being used to work on the road, the Health and Safety Executive has been informed.
Police are appealing for anyone who may have information about the collision to call police on 101 and quote log number 543 2/10/13