It happened just before 11:30 p.m. in the southbound lanes of the South Freeway between MacGregor and I-69.
The woman was driving a Harris Health System van and was involved in some type of incident with someone driving a white Mercedes, according to Houston police.
The man in the Mercedes opened fire and struck the woman in the chest, police said. The woman was able to drive to a gas station and call for help.
"According to her, the other person cut her off," said Houston police Lt. Emanuel Pavel. "She tried to go around him. It sounds a little bit like a little road rage where they went back and forth, and that's when the suspect pulled beside her on the passenger side and shot one time."
She was taken to a hospital and was expected to survive, police said.
The shooting was at least the seventh violent roadway incident in Houston over the past five days.
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