<p dir="ltr">Each year, approximately 1.35 million people die globally due to vehicle crashes, and in the United States alone, 42,915 traffic fatalities were recorded in 2021, reflecting a 10.5% increase from 2020 and an 18% increase from 2019. Driver fatigue and drowsiness significantly contribute to these fatalities, as fatigue severely impairs a driver’s alertness and responsiveness, leading to a higher risk of accident. Given the prevalence of drowsy driving accidents, it is crucial to implement advanced systems that alert drivers to their drowsy condition, significantly reducing traffic-related deaths and injuries. While these systems have shown significant effects in reducing the risks related to drowsy driving, most commercially available and widely researched alert systems heavily rely on auditory and visual sensory channels. These modalities may cause "alarm fatigue," leading drivers to ignore or deactivate the systems entirely, and result in a lower driving experience. Due to their frequent occurrence and potential annoyance, the National Highway Traffic Safety Administration (NHTSA) recommends that auditory warnings, which are the most commonly used modality in current driver alert systems, are generally unsuitable for first-stage cautionary alerts. Despite NHTSA human factors guidance, most in-vehicle warning systems consist of auditory and visual modalities, even in the first cautionary stage alerts. Therefore, advanced alerting systems that balance the functionality of alerts and driving experience, using non-audio and non-visual modalities, are needed.</p><p dir="ltr">With this motivation, the purpose of this Ph.D. dissertation work is to propose a novel approach to both olfactory and climate adaptive alerting systems and demonstrate their usability in in-vehicle engagement experiences. In Study 1 (Chapter 3), the use of behavioral metrics and physiological sensing was validated to assess drivers' cognitive states during driving. This validation laid the groundwork for the future evaluation of the effects of the proposed alerting system in Study 2(Chapter 4) and Study 3 (Chapter 5). In Study 2, the impact of olfactory and climate stimuli on drivers' cognitive states was investigated by studying time-variant changes. This investigation helped determine if the proposed stimuli can be effectively utilized in driver alerting systems. In Study 3, the proposed sensory-integrated alerting adaptive systems were developed and evaluated for their effect on drivers in a drowsy state. The evaluations focused on the systems’ abilities to provide a sufficient salient effect, sustained arousal effect, and driver satisfaction.</p><p dir="ltr">This dissertation introduces a new approach to driving alert systems to ensure both alert functionality and driving experience. Ultimately, this work offers a new direction for developing advanced alerting systems, particularly for first-stage warnings.</p>