Lucian-Sorin Todor said he made the decision to drive away after seeing 22 year old Jack Burgess lying in the road as he did not want to block paramedics or police from helping him, a court heard.
Todor, who caused the collision after crossing double white lines to overtake a cyclist, said he did not realise he caused the crash as there were no dents or scratches on his lorry.
The court heard Mr Burgess died from head injuries caused in a collision with the lorry's wheels.
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Todor has pleaded guilty to causing death by careless driving but denied causing death by dangerous driving.
Jurors at Winchester Crown Court were told that while travelling on the A32 at Warnford, near Petersfield, Todor overtook a cyclist coming up to a bend with a restricted view.
Travelling on the other side of the road was an Audi A6, a Vauxhall Zafira and Mr Burgess’s Yamaha motorcycle.
Todor’s manoeuvre onto the other side of the road left the other vehicles with little space and they were forced to brake.
Tom Wilkins, prosecuting, said: ‘Mr Burgess then braked however he came off his motorcycle falling to his offside when he had the Vauxhall in front of him.’
The court heard Todor saw Mr Burgess lying in the road but he claimed he could do nothing to help so drove away.
Todor told the jury: ‘When I saw the motorcyclist, he was getting help already. There was someone kneeling down with him and someone on the phone.
“I could not do anything because I am not medical so when I saw he was getting help I was thinking the police and ambulance would come and I did not want to block them.’
The court heard he was on the phone when the crash happened and continued the call for the two short minutes that he stopped before leaving Mr Burgess, from Waterlooville, on the side of the road.
Todor, from Waterlooville, said in a statement to police that he would have been using Bluetooth as he had an ear piece.
In the statement he said: ‘I heard a noise like a clap and looked in my driver side mirror and saw someone on the ground.’
The statement added: ‘I do not believe I caused the accident. I am extremely sorry that someone has died but I do not believe it was caused by me.
‘If I thought I was involved in an accident I would not have left.’
Motorist Rachel Wells, who was driving the Vauxhall Zafira involved in the crash, said she ‘could not believe’ the lorry driver simply left afterwards.
Todor told the court he overtook the cyclist to avoid hitting him as he popped out from nowhere as he was travelling down a road which had dark and light patches due to overhanging trees.
Mr Burgess suffered fatal head injuries as a result of the crash in June 2019 and died in hospital.
Following his death, his family revealed his organs had helped five other people.
His sister Sophie, who works for the South Central Ambulance Service, said: ‘We realised that as we were saying our goodbyes, around the country other families were coming together because their loved one was getting another chance of life.
‘Jack was a funny, adventurous and caring person who was loved by all that knew him.
‘It’s been hard for my mum, his older brother, twin sister and I, grieving for Jack but without having the positivity of knowing how Jack helped others by being an organ donor, it would have been even harder.’
The trial continues.