The incident happened outside the Crossflags garage in Cornwall Mount at about 10:40 on Saturday.
The driver was taken by ambulance to Dumfries and Galloway Infirmary but died a short time later.
The Annan Road was shut for a while for the road to be cleared.
A 72-year-old man has died in hospital following a crash in Dumfries when he apparently fell ill at the wheel.