She was rushed to New York Hospital Queens, where she was pronounced dead.
Police say the vehicle that struck her left the scene, continuing northbound on the expressway.
It was described as a dark, possibly red, four door sedan with right front end damage.
Eyewitness News is told the vehicle is believed to have crossed the Whitestone Bridge, and police were looking at surveillance camera images taken at the toll plaza.
The ensuing police investigation caused two northbound lanes to be closed for the early morning commute.
It was not immediately clear why the woman was standing on the expressway.