Interestingly enough, the 42 year old Mrs. Parks wasn’t sitting in the white section, she was sitting in a section which was first come first serve, where she was allowed (under the laws of the time) to sit. In addition, originally, the bus boycott didn’t ask for the end of segregation, just for larger seating areas for blacks and a more “humane” implementation. In fact, had the administration given in right away, segregation might have remained the practice on city buses longer than it did.
The photo below is obviously not from the day of her arrest, but actually from a bus ride later, once segregation of buses has ended. It’s what the movement achieves at great cost.