Embodiments of driver alertness monitoring systems, devices, and associated methods based on steering variability and/or lane variability are described herein. In one embodiment, a method for detecting alertness of a driver operating a vehicle includes recording a steering position of the vehicle with a steering sensor and transmitting the recorded steering position to a processor. With the processor, the method also includes deriving a steering variability based on the recorded steering position of the vehicle over time, calculating a lane variability based on the derived steering variability and a transfer function of the vehicle, and estimating an alertness of the driver based on both the derived steering variability and the calculated lane variability.
