The ERA heard the husband was angry and had threatened to come to the DDS site.
DDS project manager Craig Hooker concluded, from talking to the husband and staff, that Mr Simpson and another employee had been involved in the complaint.
He called Mr Simpson that evening and told him there had been a complaint.
Mr Simpson explained he had been waving to a DDS employee in another company truck at the intersection, not at the woman in the black Commodore.
But his manager questioned how he knew it had been a black Commodore, to which Mr Simpson replied that he liked that model of car.
DDS director Jeff Ottaway called Mr Simpson into his office the next day and suspended him from work. The labourer was dismissed two days later.
Mr Simpson raised a personal grievance claiming he was unjustifiably suspended and dismissed.
ERA member Eleanor Robinson agreed, noting there was no evidence an investigation had been launched before Mr Simpson was suspended.
There was also no evidence that Mr Ottaway had conveyed Mr Simpson's explanation, or a letter apologising for any misunderstanding, to the complainant.
"Had he done so, there is a possibility that she may have withdrawn her complaint."
Ms Robinson said the company had preferred the complainant's evidence over that of its employee, despite his good work and behaviour record, and had not considered options other than dismissal.
She ordered DDS to pay $1650 in lost wages and $5000 in compensation to Mr Simpson. Costs were reserved.