The crash happened on South Promenade in Newcastle, Co. Down shortly before 11 pm last night (Thursday, 24 August).
The victim was Geoffrey Cartwright, aged 78, from the local area.
An 18-year-old male was arrested on suspicion of driving while unfit and dangerous driving causing death.
He has been released on bail.
Police in Downpatrick are appealing for witnesses to contact them by calling 101, quoting reference 1530 of 24/08/17.
Alternatively, information can also be given anonymously through the charity Crimestoppers 0800 555 111.