Prosecutor Helen Tench said the assault had a “detrimental impact” on the traffic warden. No physical injuries were reported.
In a police interview, Doughty said he had become frustrated because the machine would not accept coins, adding that police were “more interested in ripping off a pensioner”.
In mitigation, defence solicitor Robert Hanratty said Doughty, who appeared in court in a wheelchair, accepted responsibility for his behaviour.
“He will be the first to admit that when he gets agitated, he does swear,” he said.
Hanratty added that the Probation Service recognised he suffers from anxiety.
“He very much regrets this incident. She was doing her job, and she puts up with a lot of stick.
“Unfortunately, he chose to vent his frustration on Ms Williams.”
Probation officer Julian Davies said Doughty became “very frustrated” when money repeatedly fell out of the machine and felt the warden was being dismissive.
“He deeply regrets his actions and didn’t mean to assault the warden,” he said.
The court heard Doughty, a retired HGV driver, has two previous convictions for battery and threatening behaviour.
Magistrates fined him £500 and ordered him to pay £200 compensation to Ms Williams.
He was also ordered to pay a £200 victim surcharge and £85 in court costs, bringing the total to £985.