David Hayton, 37, of West Drive, Lancaster, hit a man then punched his girlfriend to the ground, before stamping on her head in front of horrified onlookers.
The dad-of-one later claimed the couple, who had stopped to deal with a puncture on the man's bike, had assaulted him first.
Preston Crown Court heard the incident unfolded between 3.30pm and 4pm on April 19 last year on Lancaster's popular New Quay Road.
Prosecuting, Charles Brown said: " While they were stationary there the defendant, also coming in the same direction, pulled over and stopped in front of them.
"He then got out of the driver's seat and started shouting straight away, coming up to him and shouting in his face."
When the young woman asked him to leave them alone and asked what he was doing, he started to punch him to his face and body.
The woman tried to stop him and pull him away, accidentally tearing his T-shirt.
Mr Brown said: " Then the defendant transferred his attention to her. He punched her to the head then either punched or pushed her and she fell to the ground. Her head was close to the pavement.
"The defendant was standing over her and he stamped upon her head."
Horrified members of the public, including a jogger who filmed part of the attack on her phone, intervened and called the police.
Hayton got into his car and drove away but returned with his partner and another scuffle began.
The couple suffered bruising and facial injuries.
Hayton, who has previous convictions for violence, admits causing actual bodily harm and common assault.
His defence lawyer said he accepted he should have "reacted differently" and felt ashamed.
She told the court the family's dog, which he was going out to walk on the day in question, had had to be put to sleep a couple of hours before the sentencing hearing.
The Honorary Recorder of Preston. Judge Robert Altham, imposed an 18 week jail sentence, suspended for two years, with 240 hours of unpaid work and a probation programme.
He said: " You were apparently irritated by something that had happened and got out of the car. What then followed was, I'm sure you will agree, an extremely ugly incident, where you set about verbally then physically berating these two very young people.
"You do need to understand the physical consequences could have been very grave indeed."
He added the court often dealt with cases where a "permanent and utterly debilitating brain injury and sometimes death" had been caused as a result of a single blow or stamp to the head.
He added: "You need to reflect on your conduct as to what could have happened in this case.
"Happily the injury in this case was relatively slight."
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