On Friday, the court set aside the 10 counts of murder and four counts of attempted murder Humphreys had been convicted of by the Western Cape High Court on 11 December 2011.
In August 2010, 10 children were killed, while four were seriously injured when Humphreys drove his mini-bus taxi across a railway crossing, resulting in the taxi being hit by an oncoming train.
Friday's ruling saw the charges being replaced with 10 convictions on the alternative charges of culpable homicide.
"We are never going to change the reckless and irresponsible behaviour on our roads unless severe consequences are imposed by our courts on those who kill on the roads, especially when their actions result in the death of 10 children.
"While I respect the judgement delivered by the respected Supreme Court of Appeal in this instance, I do, however, feel that the consequence of a murder conviction and a 20-year jail sentence was appropriate," said Carlisle.
"The decision to reduce the sentence and convictions is therefore very disappointing as it shows that the highest courts have yet to fully understand the need for consequences as a deterrent to the dangerous behaviour we see on our roads," he added.
Road Traffic Management Corporation acting CEO, Collins Letsoalo, has previously said that South Africans needed to understand that "killing people on the road" was murder.
"South Africans are not doing the simplest of things, like wearing a seatbelt and they don't see it as a problem. It has been proven that if we can increase our seatbelt wearing rate to double what we have now, we would have a 30% reduction in road fatalities," Letsoalo said on the sidelines of a road safety conference last year.
