Driverless ride-hailing is moving beyond a handful of familiar test zones. Tesla, Amazon-owned Zoox and Alphabet’s Waymo are entering more American cities, but the three companies are arriving with different vehicles, business models and levels of public access. Waymo has begun inviting riders in Denver, San Diego and Tampa, taking its fully autonomous service to 14 US cities. Tesla now offers paid Robotaxi rides in six metropolitan areas across Texas and Florida while preparing Cybercab for fleet deployment. Zoox is adding Houston to its testing program after starting paid service with its purpose-built vehicle in Las Vegas. The expansion makes city counts less useful on their own. …