A woman was killed in a crash on the A45 on Tuesday afternoon.
The 63-year-old Rugby woman died and a six-year-old girl passenger suffered shock, but no injuries, when the car left the road and hit a tree.
A second vehicle involved in the collision near the Warwickshire and Northamptonshire border did not stop.
A 41-year-old Daventry woman was later arrested on suspicion of failing to stop at the scene of a collision. She has been released on police bail.
Both cars were travelling in the same direction on the northbound carriageway, from Daventry towards Dunchurch.
Officers at the Greys Mallory road policing unit are appealing for witnesses.