The teenager was bitten on the arm when the dog lunged at them through the open front passenger window of a stationary vehicle at the traffic lights at Rohais and Collings Road.
The incident happened at around 17:15 on Wednesday 8 June.
Police described the dog as a black and white springer or collie and said it was in a blue car with a male driver who was bald.
Anyone with information about the incident is asked to contact PC 191 Hollingsworth on 222222 or Crimestoppers anonymously on 0800 555 111.
Pictured (top): A file image of a dog similar to the one which lunged at the teenager.
