An autonomous vehicle can transition between operational modes. The readiness of a vehicle driver for a transition can be assessed, particularly when transitioning from a first operational mode to a second operational mode that has a greater degree of manual involvement than the first operational mode. It can be determined whether an operational mode transition event has occurred while the vehicle is operating in the first operational mode. Responsive to determining that an operational mode transition event has occurred, an audial sample from a vehicle driver can be collected. It can be determined whether the vehicle driver is ready or non-ready to provide the greater degree of manual involvement for the second operational mode based on the collected audial sample.