Police are investigating a road traffic collision which occurred on the M4 westbound carriageway between Swindon and Chippenham at 7.55pm on Sunday 9 October.
Four vehicles were involved in the collision, but one of the vehicles failed to stop at the scene.
The vehicles involved were an Audi A3, an Alfa Romeo Brera and an Audi Q7.
As a result of the collision, a 79-year-old female passenger who was travelling in the Audi Q7 sustained back and neck injuries and was taken to Great Western Hospital.
There were significant tailbacks following the collision.
PC Alan King, of the Tri-Force Roads Policing Unit, said: “We would like to hear from anyone travelling on the M4 at this time who may have witnessed the collision. We are particularly keen to speak to the driver of a small dark coloured vehicle involved in the collision, which sustained damage and failed to stop at the scene.
“If you were travelling on the M4 at this time, and witnessed the collision, or if you saw the fourth vehicle involved in the collision prior to, or after the incident, please get in touch.”
Anyone with information should call police on 101.