Police believe the driver collided with a 35-year-old woman at a bus stop at Mission and 30th streets around 8:10 p.m., San Francisco police Sgt. Danielle Newman said.
The woman was taken to a hospital where she is being treated for injuries that are believed to be life-threatening, the sergeant said.
"She will probably have quite a long recovery," Newman said.
The sergeant said the driver, identified as 45-year-old James Bell of San Francisco, was arrested on suspicion of DUI causing injury and a hit-and-run.
Bell remained in custody as of this morning.