Feedback from users, a measure of how comfortable people are with the idea, and if people are OK with it, then spreading the idea of driverless cars being safe

Feedback from users, a measure of how comfortable people are with the idea, and if people are OK with it, then spreading the idea of driverless cars being safe and normal (which I consider differently to PR, but feel free to ignore it). You also ensure that you're taking the same type and length of trips at the same time of day as you otherwise would be. You now also don't need an extra car. Instead of one car taking passengers and one gathering data, you only need a single car doing both. So it's cheaper and you get more information, as well as more accurate information from it.