Rock County sheriff's deputies say 33-year-old Tracy M. Fay from Janesville died in a one-vehicle rollover around 2:30 a.m. Tuesday morning.
The accident occurred at USH 14 East, one mile east of S. Avalon Road in Bradford Township.
Police say Fay was driving westbound on USH 14 when she lost control of her car on slippery roads and entered the south side ditch, hitting an embankment, causing the car to roll over several times.
She was ejected from the car and pronounced dead at the scene. The passenger, Daniel C. Tuescher, was taken to Mercy Hospital where he was treated and released with minor injuries.
Neither the driver nor Tuescher were wearing seat belts. The accident is still under investigation.