Dashcam footage has revealed a shocking road rage incident in which a car was rammed off a Canberra road.

ACT Policing is investigating the crash, which happened on Sulwood Drive in Kambah on May 7.

The footage, taken about 3:00pm on a Monday afternoon, shows a black Toyota Kluger tail-gating another car before pulling out into the emergency lane to overtake that car at the end of a "form one lane" merge.

When the other car does not slow down, the Toyota swerves and crashes into its side.

The impact causes both cars to swerve off the road, leaving the Toyota almost hitting the car that is filming the incident behind it.

ACT Policing's Sergeant Marcus Boorman said no-one was injured, but put that down to luck.

"I was shocked by what I saw," he told ABC Radio Canberra.

"The behaviour of the driver is just unacceptable."

He said the behaviour risked the life of the person in the car that was struck as well as other road users, adding there was no excuse for road rage.

"We can all acknowledge that every day we're out there we get frustrated on the roads," he said.

"But at the end of the day, you have to be aware of your surroundings, be patient, abide by the road rules.

"And nothing is that important that you have to do something stupid and put someone's life at risk."

ACT Policing is seeking witnesses or more footage of the incident.

They ask anyone with information to contact Crime Stoppers, anonymously if they wish, and quote reference 6263568.