A Ford Falcon was rammed continuously, its rear window smashed, during a road rage incident in Lyneham on Monday afternoon.

Police say it is alleged the silver station wagon was travelling northbound along Ellenborough Street when, merging from two lanes into one, the vehicle was struck on the left-hand rear panel by a white Nissan Patrol.

As the Nissan continued to ram the Ford, an item on the roof racks came loose and struck the rear window of the Ford, breaking it.

The driver of the Nissan stopped, however did not exchange any details.

Witnesses should call 1800 333000, or via the Crime Stoppers ACT website.