The offence happened in Dawson Road, Bletchley last Tuesday (March 20).
The victim, a black woman in her forties, was driving a blue Mini vehicle in the road at about 5.45pm on Tuesday.
She was manoeuvring her vehicle left onto V7 Saxon Street when a white van swerved in front of her car and into on-coming traffic.
Following this incident, both vehicles approached the Denbigh Roundabout where the driver of the van, an Asian or mixed race woman, wound down her vehicle’s window and shouted racial abuse at the driver of the Mini.
The offender then drove her van towards Fenny Stratford.
Investigating officer, PC Laura White said: “Racial abuse is unacceptable and I am determined to find the offender and bring them to justice.
“I am appealing to anyone who saw or heard the offence, or anyone with any other information about the incident to contact police immediately.
“I am sure that someone will know the perpetrator or will have some information to provide. If you do please contact police by calling 101 or visiting a police station and quoting reference number 43180085245.
“The offender is an Asian or mixed race woman, in her twenties, slim, with highlighted hair which was in a ponytail and a nose ring through her septum.
“She was wearing a grey tracksuit top and high visibility waistcoat.
“The offender’s vehicle is a white Citroen or similar box van with a tail lift. The vehicle registration started PO15.”