Apparently, most people say “thank you” to the car after getting their pizza. (“We probably want to have some UX around that, because that’s cool. It’s very human,” Farley said.) Though customers weren’t comfortable tapping in the last four digits of their credit card number as a code to open a window so they could grab their pizza, they were fine using the last four digits of their phone number.

In the summer, most people walked out to the car barefoot. “That sounds really weird, but that has a big impact on where we put the vehicle,” Farley said. “They don’t want to step on the street; there’s glass, there’s all sorts of stuff.”

All that will help Ford shape how the company builds an autonomous vehicle for delivering products. “We have to understand what the UX is on the outside of the vehicle,” he said. “Should it be a key pad? Should it be a voice assist?”

The company hopes to learn more—both about how customers interact with the cars and about how it should set up the interior of delivery-centric vehicles—in a test with delivery service Postmates, which will get started by the end of March in an as-yet-unnamed city.