The National Highway Transportation Safety Board is opening a preliminary evaluation into Tesla's autopilot feature, after the fatal crash of a Model S that was in self-driving mode, the electric automaker said Thursday. According to a blog post from Tesla Motors Inc., the car was on a unnamed, divided highway when a tractor trailer drove across the road perpendicular to the Model S. "Neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied," Tesla said in the post. The Model S passed under the trailer, with the bottom of the trailer impacting the windshield of the Model S, Tesla said. Tesla said this was the first fatality in which the autopilot feature was activated, with more than 130 million miles driven using that feature. The Palo Alto automaker said it informed NHTSA about the incident "immediately after it occurred."