And they did, until they didn't. This is not a brand new, unproven technology. It's been developing for over a decade. The car didn't hurt anyone or crash into anything - it simply did not have its lights on. The behavior to drive to a safer place for the traffic stop was intentional, per Cruise. This is something human drivers do as well. When being pulled over, it's common to pull into a parking lot or other nearby place that isn't in the driving path, for the officer's safety and convenience, in addition to allowing traffic to continue to flow without obstruction.