This paper presents a method for achieving functional safety for an automated vehicle system with respect to safe transitions between a manual and an automated driver, where any single mistake of the human driver is tolerated. Safety analysis and assessment of an implementation example show how to allocate safety requirements on Human-Machine Interface (HMI) components to handle the risks of unfair transitions and mode confusion. Results from this example show that it is sufficient to allocate safety requirements on the sensor of, and the lock of, a single lever to ensure safe transitions. No safety requirements are needed on visual feedback to the driver, e.g., displays.