When driving a car, the driver needs to be able to focus on many things at once. We have to consider traffic regulations and at the same time be able to make decisions about the most appropriate actions in a continuous stream of traffic scenarios. For this matter, VTI conducts research within the area of driver workload.
The decision making process in traffic is a constant stream of complex or simple decisions that must be timed correctly to be effective. There are many potential sources of cognitive workload. Workload can be high because the driver is unfamiliar with the roads; the driver may also be unsure of the route and need to search the road scene for relevant information (e.g. signposts and landmarks). Road and traffic complexity are also factors that could increase workload. The driver could also be inexperienced and the actual task of driving per se requires large amounts of mental effort. There is also the possibility that the driver has imported their own sources of workload in the form of non-driving related tasks. A common example of non-driving related task is mobile phone use.
Cognitive workload can also be viewed as a double-edged sword because to achieve an optimum level of performance, the level of workload must not be too high or too low. If workload levels are too low, then driver performance will also suffer and driver errors will occur. When under stimulated the human brain, unlike a computer, starts to drift from the task and thinks of other things. The brain becomes distracted with other thoughts or other non-driving related tasks are engaged to increase the brains arousal level and avoid boredom.