The spare is flat too

Coming back from the 7/11 with the morning paper. I heard the noise and only then realized what I was looking at: a woman driving a car with a flat tire. Only her flat tire is the spare tire used temporarily after a flat.
Someone else notes it and I hear the comment "that gal is driving on her flat spare" and then laughs. Not quite sure what was so funny.
She does not stop at the local garage though, she keeps going down on 16th street and disappears.