Federal regulators are investigating Tesla’s autopilot feature after a fatal crash involving a tractor trailer and one of its Model S cars. It may have been be the first fatal accident involving a self-driving car. It’s a setback for the auto maker and one that could make regulators wary. “Autopilot is getting better all the time, but it is not perfect and still requires the driver to remain alert,” Tesla says. The crash reportedly happened in central Florida, and the NHTSA notified Tesla of the investigation Wednesday.”]