Abdul Jabbar, 59, of Dudley, was sacked by National Express West Midlands in October 2015 after CCTV footage captured him running the light in King Street.
But he sued, claiming the dismissal was totally over-the-top for one mistake in an unblemished career behind the wheel.
Now, after a hearing before an employment tribunal, Judge Glyn Lloyd has ruled the sacking "unfair" and that Mr Jabbar is entitled to a compensation payout.
"The claimant is a bus driver of exemplary record," said the judge in his ruling, which was delayed at the end of the tribunal hearing in April.
"He has worked for the respondent without any disciplinary taint for some 37 years.
"He has been free of any accident or driving penalty for some 32 years.
"What he did was - and we accept it was - a five-second momentary lapse of concentration on his part by a driver who sits in the cab facing the unpredictable environment of busy city roads eight to ten hours each day.
"Considering the totality of the evidence, we find that his summary dismissal in those circumstances was disproportionate."
The tribunal heard Mr Jabbar had claimed that his sacking was an attempt by his employer to get an expensive older employee off its books.
Pakistani-heritage Mr Jabbar also claimed that a British driver would not have had the same punishment.
He pointed to the case of a colleague, who around the same time had also run a red light, but got away with a final written warning.
However, despite ruling the sacking unfair, Judge Lloyd said Mr Jabbar's age and race discrimination claims had not been proved.
The case will return to the employment tribunal next month for an assessment of Mr Jabbar's damages, unless an agreement can be reached out of court.