Uber’s autonomous vehicles have appeared on the road again in San Francisco. This follows both their departure from the city last year and Uber’s decision to temporarily halt self-driving car tests around the US due to an accident in Arizona over the weekend.

It’s returning to the road in San Francisco before resuming operations in Arizona or Pennsylvania. That may be due to its units in San Francisco using a different stage of technology than its other cars.

The Arizona incident turned out not to be Uber’s fault, though the full nature of the situation still isn’t known.