For years, the driverless car felt like a science fair project that never quite graduated. That’s changing. Robotaxis are picking up paying passengers in a growing list of U.S. cities, fleets are expanding overseas, and federal regulators are rewriting decades-old rules to make room for cars with no steering wheels. Yet anyone watching closely can see the technology is still wobbling through a tricky middle stage where ambition outpaces what the streets, the laws, and the public are ready to handle.