The crash happened shortly before 7am yesterday on the slip road opposite Spurriers Avenue, between the A645 Pontefract Road and the A162 Great North Road.
The driver of the mobility scooter, a man aged 84, was taken to hospital with serious injuries but has since died.
Police have not yet released his name.
Officers from West Yorkshire Police Major Collision Enquiry Team are investigating the collision and would like to hear from anyone who saw either vehicle in the time leading up to the collision, or anyone who witnessed the collision itself.
Anyone with information can contact the team via 101 or via the force's website, www.westyorkshire.police.uk, quoting reference 13180510120.