One thing I found quite compelling was the unpleasant realisation that the Doctor and Graham needed to *be* the white people taking up the space so the driver had to tell Parks to move. You could see they so wanted to help, but knew they couldn't.
It was important that they didn't make to that the Doctor inspired Parks, or caused the events, or anything like that. It was a strong choice to have nobody even really notice the Doctor, and for none of the primary characters agency to be altered or reduced. They all made the choices and did the things they did on their own initiative, and the Doctor had nothing to do that. Instead, she was busy dealing with a time traveller and ensuring he didn't stop it, while staying out of the way.