John Campbell, 66, had a charge of driving without due care or attention found not proven by a jury after a four-day trial.
Mr Campbell, of Glasgow, ran over John and Emma Grier in January 2011 with his 40-tonne truck, killing them both.
It was alleged that, as he set off from traffic lights in Hamilton he failed to notice the couple crossing the road arm-in-arm in front of his vehicle. He then drove off, sweeping them under the wheels of the lorry before onlookers alerted him to the accident, the court heard.
Yesterday angry scenes erupted at Hamilton Sheriff Court after the jury delivered the verdict, with Shouts of "scumbag" and "rot in hell" heard in court. Relatives of the Griers and Mr Campbell wept in court.
The family of the victims, who were both 76 and from Motherwell, North Lanarkshire, later told of their anger at the verdict.
The couple's grandson Ross Jeffrey, 32, of Motherwell, said: "Our whole family is absolutely devastated. This has been going on for two-and-a-half years and we have been left with no justice.
"The jury have let down my grandparents and our family. How they can reach that verdict after listening to all the evidence in the case is beyond me. I just hope Mr Campbell and the jury members can live with themselves.
"The verdict should have been guilty or not guilty. The not proven verdict is just a cop-out and should be done away with."
The jury had earlier heard defence lawyer Simon Collins describe the incident as a tragedy.
He said: "The decision by the Griers to cross the road was catastrophic. There is nothing we can do to alter things. During this journey Mr Campbell's lorry collided with the Griers who died shortly after.
"The pedestrians were not covered by the mirrors on the lorry. If he had looked he would not have seen the couple.
"Mr Campbell was looking exactly where he should have been, he was doing everything expected of him.
"There is nothing to say he should have seen them. It is a tragic fact that they weren't seen."
The trial had heard that Mr Grier had desperately banged on the front of the truck to get it to stop as it moved towards them.
CCTV footage also showed the couple disappearing under the wheels of the lorry before reappearing in the middle of the junction as the lorry drove off.
Expert witness Kevin Taylor, 56, had told the jury he believed the couple would have been "invisible" to Mr Campbell.
He said: "Mr Campbell did not have a good clear view of them when they set off across the road. There were a lot of things to observe and consider at this busy road junction for the driver.
"If he had checked his mirrors he would not have seen any pedestrians - they were not in the range of those mirrors. The couple would have been invisible."
Mr Taylor also told jurors that, given the noise of the lorry's engine, Mr Grier's banging on the truck would have gone unnoticed.
The trial also heard from expert witness PC Ewan Thomson, 48, of Police Scotland.
He told the court he believed the Griers would have been visible from the truck driver's position because an adjacent bus driver had claimed to have seen them.
Last year, the Scottish Government published a consultation on scrapping the not-proven verdict from court trials as part of a radical shake-up of the justice system. It is unique to Scots law and was branded "that bastard verdict" by the novelist Sir Walter Scott.