Adris Hussain was at the wheel of his Peugeot when it pulled out of the Bentley branch of McDonald's in front of a vehicle being driven by Raja Shahid on October 9 2018, a judge heard.
Mr Shahid was not upset by the manoeuvre and remained calm as the 22-year-old defendant deliberately drove very slowly in front of him, Wolverhampton Crown Court was told.
Eye witnesses said this continued for several minutes until Hussain came to a standstill in Queen Elizabeth Avenue, gave way to one vehicle and kept waving his arm out of the window leading Mr Shahid to presume he was being encouraged to overtake the stationary vehicle but when he did the Peugeot drove into the side of his car, revealed Mr Christopher O'Gorman, prosecuting.
Both men got out of their car and confronted each other as the defendant demanded money to pay for the damage to his vehicle and reached into the Peugeot to seize a crow bar.
He swung the weapon at the head of Mr Shahid who saw the blow coming and blocked it with his left arm which was fractured by the impact before a second swing of the weapon missed as other motorists called the police.
The victim took a picture of the Peugeot as the defendant came to his senses and left the scene empty handed to drive his seven month pregnant wife to hospital for a check up following the drama.
The prosecution said mystery surrounded the real reason for Hussain acting in the way he did but Mr Gurdeep Garcha QC, defending, suggested: "It was a spontaneous outbreak of violence after he wrongly perceived what he thought was some sort of aggression from the other man.
All that he achieved was to aggravate rather than help the condition of his wife."
The defendant from Hill Street, Wednesbury was traced and arrested on December 1 2018.
He pleaded guilty to causing grievous bodily harm with intent and having an offensive weapon.
He was jailed for four years six months by Recorder Michelle Heeley QC who said: "You lashed out at Mr Shahid who was fortunate not to have been more seriously injured."