He pleaded guilty to careless driving causing death and was sentenced before the Invercargill District Court last week.
Judge Mark Callaghan released court documents to the Otago Daily Times that revealed the cause of the crash was a mystery.
Houlden was driving his SsangYong vehicle north and approached the area known as the Paterson passing lanes - "characterised by bends and a number of undulations", according to a police summary.
He was at the back of a line of three cars and the one at the front veered left to let those behind pass.
The summary said the driver of the front car slowed as he pulled over because his car was getting showered with grit. The road had been sealed two days earlier.
Both trailing vehicles passed the driver but Houlden drove off the left side of the road, over a bank and into a paddock.
His vehicle rolled several times and came to rest 100m from the road.
Houlden, a former professional driver who had no previous convictions, had no memory of what happened.
However, his counsel Katy Barker argued her client should not be disqualified from driving because of "special reasons".
The road had been resealed two days before the crash, there was no temporary speed limit and no signs to warn drivers of loose grit until they were on it, she told the court.
Judge Callaghan said he had considered the matter "very carefully" and noted there was no indication of the speed Houlden was travelling or the state of his vehicle.
"While to an outsider, the loose gravel might have been a contributing factor, there is [no evidence before me that says it led] to the loss of control," he said.
As a result, the judge ruled there were no such special reasons and banned Houlden from driving for six months.
"No penalty that this court imposes will reflect the loss that you have suffered as a result of this tragic event," Judge Callaghan said.
