On August 13, 2021, NHTSA?s Office of Defects Investigation (ODI) opened a Preliminary Evaluation (PE21-020) to assess the performance of Tesla?s Autopilot system (a system characterized by Tesla as an SAE Level 2 driving automation system designed to support and assist the driver in performing the driving task) available in Tesla vehicles. The investigation opening was motivated by an accumulation of crashes in which Tesla vehicles, operating with Autopilot engaged, struck stationary in-road or roadside first responder vehicles tending to pre-existing collision scenes. Upon opening the investigation, NHTSA indicated that the PE would also evaluate additional similar circumstance crashes of Tesla vehicles operating with Autopilot engaged, as well as assess the technologies and methods used to monitor, assist, and enforce the driver?s engagement with the dynamic driving task during Autopilot operation.PE21-020 is upgraded to an Engineering Analysis (EA) to extend the existing crash analysis, evaluate additional data sets, perform vehicle evaluations, and to explore the degree to which Autopilot and associated Tesla systems may exacerbate human factors or behavioral safety risks by undermining the effectiveness of the driver?s supervision. In doing so, NHTSA plans to continue its assessment of vehicle control authority, driver engagement technologies, and related human factors considerations.The attached Detailed Summary further describes NHTSA?s review to date and the basis for upgrade to an EA.