| Stress among drivers has been shown to be caused by environmental and personal factors. Additionally, driver response to stress through compensation efforts serves to adjust the driving environment, and is also dependent on driver characteristics. To date, the causation of stress among drivers and the effect of stress on driving behaviors have been studied separately. This research seeks to develop a framework for assessing both the sources of stress and the response to stress simultaneously. This is done through the use of a control theory model. The proposed model is developed by modifying existing representations of driver stress based on a set of survey analyses and by using a literature review to show how drivers alter the inputs to the model based by compensating for stress and the environment. Upon identifying the source of driver stress and incorporating the effects of driver compensation, a proposed model is presented and discussed. Various components of the model, such as environmental inputs and compensation, are then validated experimentally to demonstrate how to test the model. This is done using both surveys regarding stress levels, as well as an on-road study which measures stress using heart rate variability. Differences in subjective and objective assessments of stress, and conclusions about sources and nature of stress while driving are also discussed. From these studies, it is determined that stress is associated with dynamic traffic patterns more than the fixed driving environment. Additionally, it was found that the effect of stress on age and gender is dependent on the source of stress. Finally, the ability of drivers to control stress levels through specific driving actions is shown. This new model allows for the development of new driving systems and environments that not only reduce stress, but work with the driver to reduce the amount of compensation required by the driver in order to optimize stress levels. As a result, new systems will not only reduce the stress level of drivers, but will also allow the driver to attend to a greater range of driving tasks, improving performance, and reducing the risk of crashes and injuries. |
