State police say the 25-year-old was struck by a pick-up as she walked on the median of the roadway near Mannheim Road in Westchester at about 6 a.m.
The crash backed up traffic for miles.
Troopers say the woman had been arrested a few hours earlier for driving the wrong way on the expressway and charged with drunk driving. She was released on bond.
Investigators are trying to find out how she ended up walking in the median of the expressway, where she was struck by a pickup truck.
