Ralph Parker was stopped after he drove through a toll booth on the Sunshine Skyway, Traffic Homicide Investigator Michael Jockers said. The toll taker called police, he said.
Parker was not likely to face charges because he did not appear to know what happened or where he was, said Bruce Bartlett, chief assistant in the Pinellas-Pasco County State Attorney's Office.
"He may have somewhere in his mind have realized it was a crash, but immediately forgot about it," Jockers said.
The victim's leg was severed in the Wednesday night crash, police said. The man, whose name was not released, was 52.
Parker had renewed his license in 2003.
"That was the one thing he had, to get in his car and just drive for the sheer enjoyment of driving," Jockers said. Parker lived alone after his wife died in 1998, authorities said.