Intelligent Transportation Systems (ITS) refer to an integrated group of technologies which can improve safety, reduce congestion, enhance mobility, minimize environmental impact, save energy, and promote economic productivity in our transportation system. A driver-centered design philosophy will promote these benefits. These advanced technologies will thereby enhance the safety and efficiency of automobile transportation. This research dealt with In-vehicle Routing and Navigational Systems (IRANS). IRANS provide drivers with information about how to get from one place to another, information on traffic conditions, and recurrent and non-recurrent urban traffic congestion.

The problem studied in this research was whether performance on navigation tasks can be predicted by cognitive theories (Multiple Resource Theory, Stimulus-Central Processing-Response Compatibility Theory, Recoding Mechanism Theory, and Dual Coding Theory). A secondary problem was the determination of the relationship between navigation and spatial ability. Spatial ability has been linked to map reading performance. Issues addressed included display modalities and information processing codes. The effect of different display modalities on driver performance and workload was the first issue. The different display methods investigated were visual systems (current dashboard mounted display types) and auditory systems (computer generated voice communication systems). The second issue was the effect of different information processing codes on driver performance and workload. The information processing code determines the method used to present information to the driver using the display; in this research both verbal and spatial codes were considered. Verbally coded information consists of a series of sequential directions (for example, "go to the next street and turn right"), while spatially coded information is presented using a map display for visual systems.

The results indicate that the best cognitive theory for predicting navigational behavior is the dual coding theory. Subjects not only performed better, but also preferred navigational aids where the navigational information was presented in more than one way. This indicates that designers and engineers should develop navigational aid displays to incorporate redundant navigational information. Some differences for navigational performance were shown for high versus low spatial ability subjects, but the subjective measures of workload and preference did not show any differences.