If you had asked earlier, I would have explained further what I meant.
Carey must have been driving erratically long before she got near her destination. The cops were undoubtedly monitoring her progress, wondering where she was going. I've driven many tens of thousands of hours and know exactly how this works. When the police realized she might be headed for the WH, they purposely waited in the right spot to do their traffic stop, knowing very well, she would likely panic as a result of the timing involved. They were right and got their wish. They probably hadn't blown anyone away for quite awhile and were bored, so decided to catch a little thrill.