A taxi rolled onto its side, injuring a woman in her 20s, after being hit by a car that failed to stop at the scene.
It happened at around 10.25pm on the Simpson roundabout junction between H9 Groveway and V8 Marlborough Street.
The black Skoda Octativa, which was being used as a taxi, was hit while on the roundabout by what is thought to be a red Audi A4.
The injured woman was taken to Milton Keynes Hospital for treatment.
Anyone who witnesses the collision or with information that can assist the investigation should contact PC Christopher Ruvolo-Jones at the Milton Keynes Roads Policing base on the Thames Valley Police 24-hour Enquiry Centre telephone 101, quoting URN 1583 15/11.