The accident between Riccall and Barlby caused rush hour chaos from 2pm yesterday, with the road only reopening at 7pm.
North Yorkshire Police said this morning that the man was in serious condition at Leeds General Infirmary.
Early indications are that the man was in the carriageway when the accident happened.
Also in the news: Pedestrian killed in collision with car on Leeds roadDeployment manager Victoria Henderson said they were not in a position to name the man, but had spoken to his next of kin.
She said: "Thankfully his injuries look at this point not to be life-threatening, but he does remain in a serious condition.
"We are still investigating and it would be wrong to speculate, but early indications are that he was in the carriageway."
Drivers were warned to find alternative routes following the accident.
Ms Henderson apologised for the delays yesterday, but said investigations needed to get underway.