It's an 18-hour trip, which breaks down into six shifts of three hours each. Or, alternatively, we could break it down by mileage.
9 seconds sound clip from the When Harry Met Sally... movie soundboard.
You can hear this line at 00:04:24 in the Blu-ray version of the movie.
Quote context
[...]
- Sorry.
- I miss you already. I miss you. I miss you already. Bye.
- Bye.
- There's a map on the visor that I've marked to show the locations where we can change shifts.
- Grape?
- No. I don't like to eat between meals.
- Why don't you tell me the story of your life?
[...]