The National Highway Traffic Safety Administration (NHT) has escalated its investigation into Tesla's "Full Self-Driving" systems, which may make it difficult for drivers to use in reduced visibility conditions. The probe involves 3.2 million Tesla vehicles, including the Model S, X, 3, Y and Cybertruck EV. The NHT has raised its investigation to an "engineering analysis" after numerous complaints about FSD being used within 30 seconds of a crash.