Detectives are investigating an aggravated robbery that occurred on William Hovell Drive in Aranda on Monday night.
Police received reports at about 6pm of a two-vehicle collision at the intersection of William Hovell Drive and Coppings Crossing.
One of the vehicles was a red Suzuki Vitara, containing two males and one female.
Police also received reports from that location that the male driver of this car, armed with a knife, approached a third vehicle, which had stopped to assist.
The man demands for the vehicle and both occupants complied, exiting the vehicle.
The offender then made a U-turn, collected his two passengers and continued south towards the City in the red Honda Civic with ACT registration plates YGT63R.
The male driver is described as Mediterranean in appearance, 178cm tall, with dark features, stubble and a goatee-style beard, and was wearing a black and white flannelette jacket.
The red Suzuki Vitara driven by the alleged offender involved in the collision was reported stolen.
Police urge anyone who may have been in the Aranda area at the time or has any information that could assist police to contact Crime Stoppers on 1800 333 000 or via the website www.act.crimestoppers.com.au. Please provide reference number 5970207.
Information may be provided anonymously.