Houston police said the wreck happened on the northbound feeder road of the Southwest Freeway near Bellaire Boulevard at about 9:30 a.m.
Detectives said the woman was driving in the far left lane of the Southwest Freeway and all of a sudden crossed all the lanes, drove across a grassy median and crashed into the bus.
METRO officials said they believe the driver had a medical emergency.
The woman, whose name was not released, was taken to a hospital, where she later died.
The bus was on a layover, meaning no one was inside the bus, METRO officials said.
The feeder road was closed to traffic for several hours while police investigated. It was reopened at about 11:30 a.m.
SOURCE: click2houston.com