Martha Young was making her way to the gym where she was due to meet David, 26, when she saw a badly damaged car against a tree.
Mrs Young, 60, whose pipe fitter husband was killed in a helicopter crash in the North Sea in 1992, was later informed her son, an electrician, was the victim of the collision.
She raised an action at the Court of Session, Edinburgh, suing the car driver following the death of David, who was hit by a Vauxhall Vectra as he walked on the pavement of Danes Drive, Scotstoun, Glasgow, on June 1, 2010.
Motorist Arthur MacVean, then 63, of Northland Drive, Glasgow, was jailed for four and half years in 2012 at the High Court in Edinburgh after being convicted of causing death by dangerous driving. The speeding driver lost control of the car, which ran up on to the pavement.
Liability in the civil action was admitted but the judge had to assess the amount of damages and whether Mrs Young was a "secondary victim" that would entitle her to enhanced compensation.
Lady Rae said she was satisfied Mrs Young should be classed as a secondary victim. The judge said: "On the evidence I heard, I was of the view the pursuer (Mrs Young) was clearly very upset before she had had the death confirmed."
The judge said Mrs Young began to feel uncomfortable very shortly after viewing the wrecked vehicle and her suspicions about her son's involvement began fairly soon and she was distressed before police confirmed his identity.
The court heard Mrs Young, of Westerton Avenue, Bearsden, East Dunbartonshire, and her son had a very close relationship. The judge said: "She spoke of him as taking over some of the roles of his father, such as undertaking jobs in the house. She described her son as supportive and as being a 'model son'."
Mrs Young said: "He was a very generous man. Anything you asked him to do he would just do for you."
Unusually she had not seen her son for some days before the fatal incident but had agreed she would see him at the gym they attended.
Mrs Young, a child development officer, had parked her vehicle and was making her way to the gym when she saw the damaged car.
Lady Rae said in her judgement: "Her immediate thought was that someone must have died. Her initial reaction was one of relief that her children could not be involved as her son did not drive and her daughter was at home."
Mrs Young started her exercise class but after the warm-up stopped for a drink of water and noticed six missed calls on her phone.
"At that point she became scared. The calls were from her daughter Stephanie, whom she phoned to discover that police had been at the house."
She told a friend she thought David was the victim and went to check whether he had signed in and found he had not.
Police came into the gym and asked her name as she kept shouting: "Is it David?" She was asked if he had a tattoo and when she confirmed it, was told he was dead.
"At that point she remembers screaming and shouting words such as 'I don't think I can go through this again. I can't do this.', said the judge.
Mrs Young told the court that following his death she was unable to visit places where she used to meet her son, including the gym.
Lady Rae said: "The pursuer described having visions of her son walking in the street with his backpack on. She then sees a vehicle and her son being hit into the air and ending up on the other side of the road. She described having dreams and nightmares where she sees these images when she awakes."
The award included £80,000 for loss of society, £30,000 for personal services, £35,000 for pain and suffering, £80,000 was agreed for loss of earnings and services and £6,250 for the cost of psychology treatment.