The firm technically resumed driving in July, but only in a human-operated mode. That same month, Pennsylvania's DOT also issued driverless car testing guidance that both requires testing notifications and collects driving data from companies twice a year. Uber wasn't in a rush, however, and only asked for permission to resume tests in November.

At this stage, the questions revolve primarily around safety. Uber has promised more safeguards for the next time around, including the presence of two human observers, better training, closer monitoring and limits on working hours. It also recently hired an NHTSA veteran to help its autonomy efforts. However, it's not clear how much the technology itself has improved since the Arizona crash. Officials will likely keep a close eye on Uber's tests to make sure the chances of a second tragedy are very low.