This research considers the efficacy of auditory alert systems for semi-autonomous vehicles from the perspective of the neurological processing of multiple modes of information. The present work reports on how the auditory processing of deviant and standard stimuli is impacted by age and workload conditions at regions of the brain involved in the auditory processing pipeline. Electroencephalography (EEG) and behavioural data from older and younger participants were collected. Participants completed a visual memory task with low- and high-workload conditions along with a novel paired-click paradigm. EEG results showed that in the low-workload visual task condition both groups partially overcame the redundancy effect of the second paired tone when a salient stimulus was presented. In contrast, P200 neural responses to these oddball tones were attenuated in older adults in the high-workload conditions of the visual memory task. These findings have implications for how alerting systems are implemented in semi-autonomous vehicles.