Jeffrey Cruickshanks ran after the tractor unit driven by Paul Garrett and caught up with it after it got stuck in traffic at Crowness Crescent, in Bellshill, North Lanarkshire.
Mr Cruickshanks, of Myers Court, Bellshill, told a court that he knocked on the driver's cab window and described the other driver as being oblivious to having hit his BMW Z4.
He pursued a compensation action following the collision at a roundabout in Bellshill against insurers Amlin UK at the Court of Session in Edinburgh with the amount of damages agreed, although liability was contested.
Lord Bannatyne said he found Mr Cruickshanks to be credible and reliable and an impressive witness.
The judge said his version of events seemed "highly probable", that the lorry driver was high up in his large tractor unit with the added problem of blind spots in his wing mirrors and failed to see the small sports car in a left hand lane.
Lord Bannatyne said: "Mr Garrett was not aware of colliding with the car until told of this afterwards by the pursuer (Mr Cruickshanks)."