The woman was standing on a train platform in Hillsboro, Ore. when she began to sway and fell onto the track.
An approaching commuter train conductor spotted her and stopped just inches short of the woman's body.
The conductor said he saw her moving close to the edge of the tracks and pulled slowly into the station.
A transit employee helped the woman until paramedics arrived.
According to rescuers, the woman had a medical condition that caused her to fall.