The crash happened around 5:30 a.m. in the area of 37th and Chestnut in the University City section of Philadelphia.
Investigators say the cab swerved from the middle land to the left lane, hitting two other cars before striking a pole on the sidewalk. The 64-year-old cab driver was pronounced dead at the hospital shortly after 6:00 a.m.
Police now believe the cab driver suffered a medical emergency prior to the accident. Investigators on the scene had said earlier on Tuesday that the case may have been a hit-and-run, but later discounted that possibility.