Kyneton police said they took a call from an off-duty police sergeant about a car of possible police impersonators driving along the Calder Freeway towards Bendigo about 2pm. 

Police then intercepted the car just outside of Woodend on the Calder Freeway and discovered the three occupants were registered Victoria Police Historical Society members. 

One of the police officers who intercepted the vehicle said the trio were wearing "quite old uniforms, from about 20 years ago" in preparation for a Victoria Police Historical Society gathering in Bendigo tonight.

The officer said until the occupants identified themselves as historical society members, Kyneton police thought they might have some police impersonators on their hands, which is a serious offence.

He said the historical society members were not doing anything wrong or impersonating police.