Man smashes car window with 'tow bar' in road rage attack

Shocking video has emerged of a man pummelling another car's window with an object during an angry outburst on a Melbourne road.

The footage shows an armed man emerging from a white ute approaching a car stopped at the traffic lights in St Albans on Thursday afternoon.

He then forcefully hits the window using what appears to be a tow bar, causing glass to shatter.

9NEWS has been told the victim, 21, was travelling in the area in his car when he noticed the ute driving erratically and cutting him off.

The car driver claims he signalled to the ute driver that he was acting dangerously, prompting the violent outburst. 

Another man in the ute spat at the 21-year-old's car off-camera.

Police were called to the scene, and have since told TODAY Show they are investigating the incident.