Riall, a chief executive of Serco, was caught by a police patrol car in Newmarket, Suffolk, which clocked him reaching 102.92mph.
He was travelling in a blue Volvo on the eastbound section of the A14, where the speed limit is 70mph, just before 1pm on January 4.
Riall, 49, of Ufton Nervet, near Reading, was banned from driving for six months by magistrates in Sudbury after having six points added to his licence for the offence.
The former soldier is responsible for installing and maintaining speed cameras, the court heard.
Addressing magistrates, Riall said he would like to "formally apologise" and added: "In my role I am all too aware of the consequences of speeding."
The court heard that the married father of three had two previous motoring convictions, including a past speeding offence, from 2006 and 2007.
At the time of his latest offence, Riall had been driving a blue Volvo estate to visit friends in Newmarket, before attending a business meeting in Norwich.
He told the court that driving conditions had been good and there was little traffic on the road. He said that he had told the police officer who stopped him that he believed he had been travelling at 90mph.
He said: "Of course, while I have had a number of fixed penalty notices in the past, this is the first time I have exceeded the speed limit to this degree."
He added: "I would like to make it clear that I do acknowledge and accept that my speed was excessive and the offence merits points on my driving license. I would point out that a potential ban would be a significant punishment on me as an individual."
He told magistrates that he travelled the "length and breadth" of the country in his role and clocked up 30,000 miles a year.
He said his children were all in private education and any ban might affect his "long-term aspirations" to keep them in their current schools.
He estimated that hiring two personal drivers for the duration of a six-month ban would total ?30,000.
In asking magistrates not to impose a penalty that would take him past the 12 points mark, which leads to an automatic ban, he said: "You will be aware that this offence has caused some considerable personal embarrassment."
But magistrates rejected Riall's plea.
Magistrates' chairman David Hooley said: "You pleaded guilty to speeding and for this offence your licence will be endorsed with the full six points."
He said this meant a six-month driving ban would be imposed.
Riall was also fined ?300, and ordered to pay ?46 towards prosecution costs and a victim surcharge of ?15.