Across the span of the SAE International-defined Levels of Driving Automation, human drivers occupy a diverse range of responsibilities and authority on the vehicle movement and the monitoring of the outside environment. From both a technological and a regulatory perspective, there is a gap that divides lower levels of automation (L1 through L3) and higher levels of automation (L4 and L5). For those vehicles that require the cooperation between a human driver and the autonomous technology, it is important to ascertain the safety consequences of such a design choice. It is also important to understand what the transition between automated driving and manual driving entails for the human driver, as well as for the surrounding traffic. This SAE EDGE¿ Research Report investigates unsettled issues concerning what is commonly referred to as "semi-automation," including an overview of the role of human drivers, the quantification of the "transition-to-manual" problem, the role played by L3 toward full automation, and regulatory and moral considerations surrounding the deployment of these vehicles. NOTE: SAE EDGE¿ Research Reports are intended to identify and illuminate key issues in emerging, but still unsettled, technologies of interest to the mobility industry. The goal of SAE EDGE¿ Research Reports is to stimulate discussion and work in the hope of promoting and speeding resolution of identified issues. SAE EDGE¿ Research Reports are not intended to resolve the issues they identify or close any topic to further scrutiny.