A young couple were driving along the Western Ring Road, Tullamarine, east-bound at about 7.25pm when they noticed a 1998 blue Holden Commodore station wagon travelling closely behind them.

The car moved up parallel with their vehicle and the driver appeared to be angry - he then produced a handgun and pointed it at the couple.

The victims sped away from the Commodore which was last seen taking the Sharps Road off-ramp. There were no shots fired and no injuries.

Hume Detective Leading Senior Constable Cos Costa said the victims were "quite shaken'' by the incident but there was no reason to believe they would be subject to further attacks. He said it did however indicate an increasingly violent driving culture.

"The incident on this couple appears to be totally random,'' Detective Leading Senior Constable Costa said.

"It's certainly getting to be increasingly prevalent, this violence relating to traffic incidents.

"This is not an isolated incident of firearm use in traffic.''

The man police wish to speak to is believed to have a distinctive, vibrantly-coloured tattoo covering his right arm. He is described as Caucasian and in his 40s with a thin to medium build, grey, receding hair and was wearing no top.

Iinformation to Crime Stoppers on 1800 333 00 or visit www.crimestoppers.com.au