The complexity of operating in an urban environment is complicated by multimodal interactions with bicycles, emergency vehicles, pedestrians, etc. A fully-automated transit vehicle would need to be able to distinguish between bystanders and would-be passengers, who are actively walking toward the vehicle or waiting at a designated stop.

FTA is exploring potential non-technical challenges, such as federal policies regarding procurement, accessibility, labor, and other topics. The existing policies were all written with the assumption of a human operator.