Advanced driver assistance systems (ADAS) are an increasingly common feature of modern vehicles. The influence of such systems on driver behavior, particularly in regards to the effects of intermittent warning systems, is sparsely studied to date. This paper examines dynamic changes in physiological and operational behavior during lane departure warnings (LDW) in two commercial automotive systems utilizing on-road data. Alerts from the systems, one using auditory and the other haptic LDWs, were monitored during highway driving conditions. LDW events were monitored during periods of single-task driving and dual-task driving. Dual-task periods consisted of the driver interacting with the vehicle’s factory infotainment system or a smartphone to perform secondary visual-manual (e.g., radio tuning, contact dialing, etc.) or auditory-vocal (e.g. destination address entry, contact dialing, etc.) tasks. Driver physiology and behavior were recorded and analyzed during pre-LDW event and post-LDW event epochs. The percentage changes between pre-event and post-event measures were calculated to normalize for differences between vehicles. Changes in heart rate, skin conductance level, and steering wheel angle were observed after LDW events during single-task and dual-task driving periods. These metrics varied between single-task and dual-task driving, and between pre-event and post-event epochs. These results suggest a relationship between a driver’s demand level and the driver’s response to a lane departure warning signal.