National Autonomous Vehicle Day is observed worldwide every May 31. This day celebrates the progress of the autonomous vehicle industry and the opportunities it presents for technological advancement. The holiday was created in 2017 by Emerging Prairie, a nonprofit organization in North Dakota, and Marlo Anderson, founder of National Day Calendar. It aims to highlight the advancements in self-driving vehicles, which utilize sensors, cameras, radar, and artificial intelligence to navigate with minimal or no human input. The history of autonomous vehicles dates back to the 1920s, with significant developments occurring in the following decades, including the introduction of cruise control by Ralph Teetor in 1948 and the unveiling of the first semi-autonomous car in 1977. The Society of Autonomous Engineers has established a five-level classification system for autonomous driving, with current offerings including SAE Level 3 vehicles from Honda and Mercedes and Level 4 self-driving taxis in limited areas.