The woman was fatally struck around 5 a.m. by a 70-year-old man who was traveling southbound in a 2006 Chevrolet sedan on the expressway near 233rd St., said an NYPD spokeswoman.
The driver stayed on scene and no charges have been filed, police said.
It is not known why the woman was walking down the middle of the busy expressway, police said.
Traffic is still slow in the area as police investigate the accident.
Check back to Daily Voice for updates.
Click here to follow Daily Voice Armonk and receive free news updates.