A woman driver was assaulted in Meadow Sweet Road, Rushden, on Sunday, December 2.
At some time between 7.30pm and 7.45pm, the woman approached the junction with Bedford Road and was blocked in by a small red Mercedes car driven by a man who had a young girl, aged two or three, on his lap.
The Mercedes was then joined by a black BMW, which pulled alongside the Mercedes and blocked the Bedford Road.
A police spokesman said: “The driver of the Mercedes was verbally abusive towards the woman while still seated in his car.
“The man then got out of the Mercedes and approached the woman’s car, opened the driver’s door and verbally abused her again.
“He then shut the door and walked away, only to turn back, open the door again and this time spit in the face of the woman.”
The Mercedes then drove off with the BMW in the direction of Rushden.
Witnesses to this incident, or anyone with information about it, can call Northamptonshire Police on 101 or information can be given anonymously to Crimestoppers on 0800 555111.