A 32-year-old man died after his Peugeot Tweet scooter collided with a Vauxhall Vivaro van.
The crash happened at around 4.55pm on Sheepwalk Lane in Castleford.
The van had been travelling from Ferrybridge towards Castleford and the scooter had been travelling in the opposite direction.
The rider of the scooter, a North Yorkshire man, suffered severe injuries and later died. He has not yet been named by police.
PS Carl Quinn, of the Major Collision Enquiry Team, said: “Investigations are ongoing into this tragic incident.
“I would like to speak to anyone who saw the collision or the manner in which either vehicle was being driven in the moments leading up to it.”
The driver of the van had been arrested on suspicion of causing death by dangerous driving and driving over the prescribed limit.
He was later released on bail.
Anyone with information should call the Major Collision Enquiry Team on 101.