The National Highway Traffic Safety Administration (NHTSA) has initiated a probe into Tesla's Full Self-Driving software following four incidents in low-visibility conditions, one of which resulted in a pedestrian's death. The investigation aims to determine the software's ability to detect and react to reduced visibility due to factors like fog and sun glare. This comes on the heels of CEO Elon Musk's recent unveiling of a robotaxi prototype. Tesla's Autopilot software previously faced scrutiny, leading to a closed investigation after 13 fatal crashes. Additional legal challenges are also looming for the company.