The U.S. National Highway Traffic Safety Administration's Office of Defects Investigation said in September 2026 it had opened a federal probe into Comma.ai's aftermarket hands-off driver assistance technology after five reported crashes, including two fatal incidents that killed three people and four crashes that injured up to 11. The crashes involved devices failing to detect or respond to slow or stopped vehicles in the same lane; some may have involved modified third-party versions of openpilot.