The former Celtic and Hearts player, who is now in charge of Dundee, was caught speeding in his BMW 7 Series in Motherwell, Lanarkshire, in April 2012.
Hartley appeared at Hamilton Justice of the Peace Court, where he admitted the charge.
However, even though he has now totted up 12 penalty points, he will not be disqualified from driving because he convinced a Justice of the Peace he needed to his licence.
The 37-year-old had asked for an exceptional hardship hearing in a last attempt to keep his licence.
He was successful but was still fined £750 and given 28 days to pay.
The hearings are held to give drivers the opportunity to prove a driving ban would cause them "exceptional hardship", normally in relation to finances and job prospects.
Hartley, of Hamilton, told the hearing he needed his licence to travel from Dundee to see his children, his mother and to work as a football manager.
He told the court: "I see my kids on a Wednesday and at weekends, I drive down late on Tuesday so I can take them to school.
"If I didn't have a car it would affect my relationship with them greatly, they are at an important stage in their lives.
"My mother lives in the Hamilton area and I try to see her twice a week. She had a stroke six years ago and suffers tinnitus, so it is vital I see her. I sometimes stay with her because she does not like being alone sometimes.
"I do a lot of scouting work as part of my job all over the country. I have to see players personally, I sometimes work 80 hours a week.
"We are a community club so I go out and visit schools as well, we have 35 in a partnership.
"I use my car six or seven times a day, I am always out and about, it is vital I have a car.
"It would be detrimental to the club and the community if I did not have the car, I would not be able to do my job."
Dundee chief executive Scot Gardiner said: "He works seven days for us and is the hardest working manager I have ever seen.
"It is imperative he is mobile to go out and scout players and do his job.
"We would have to employ three drivers to drive him about if he lost his licence and that would not work with our budget.
"He could do a version of his job without a licence, but he wouldn't be able to do the job we need him to do. I believe it is crucial he keeps his licence and I would not be here today if I didn't think that."
Justice of the Peace Amjid Bashir said: "Having heard the evidence, I am satisfied the exceptional hardship has been proved because of the effect on Dundee Football Club and the wider community."