Jordan Bagley, 21, was charged with causing serious injury to Colin Cowman by dangerous driving, following the accident in west Cumbria.
The collision happened on the A5086 at Wood End, between Cleator and Egremont, on the evening of June 21, last year.
Bagley was speeding on the wrong side of the road.
Mr Cowman suffered serious multiple injuries in the collision.
Firefighters were called to cut him free from his vehicle, where he was trapped for almost an hour.
After being taken to the Cumberland Infirmary, Carlisle, Mr Cowman, from Whitehaven, was transferred to Newcastle’s Royal Victoria Infirmary for specialist treatment.
He remained in hospital for almost three weeks and a surgeon later described the injuries he suffered as “serious and potentially life-threatening”.
At Carlisle Crown Court, Bagley pleaded guilty to causing those injuries to Mr Cowman by dangerous driving.
His case was adjourned to May 13, when he will be sentenced following the preparation of a background report.
Bagley, of Chaucer Avenue, Egremont, was granted bail until then by Judge Peter Hughes QC.
But the judge warned him the offence was so serious he could receive a jail term.
“This is a case where you were driving far too fast on the wrong side of the road,” Judge Hughes told Bagley.
“There is a possibility of a prison sentence as a result of what you have pleaded guilty to.”
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