He had been walking home because he was unable to book a taxi.
Lorry driver Richards, 38, of Morgan Street, Blaenavon, had denied causing the death of Rhys Dobson by driving without due care and attention.
He was convicted by a jury following a trial at Cardiff Crown Court.
Richards maintained he thought he had driven over a washing machine or fridge on the dark country road during the early hours of the morning.
Ieuan Bennett, representing the defendant, said in mitigation his client had shown remorse for his actions and had suffered “flashbacks and nightmares”.
His barrister added: “He has been assessed as presenting a low risk of reoffending “He has three young daughters and is a dutiful father.”