part, started with the perspective of the driver, and stressed the importance of adapting the system to what is possible from the driver's point of view. To adapt different RTI systems, and combinations of different RTI systems, to drivers' possibilities and limitations, the project developed the notion of an "information refinery" ( Micron, 1993) that could prioritize and delay information, and present it in such a way that the driver understands it quickly without being distracted or overloaded.
To summarize, a psychological (cognitive as well as attitudinal) perspective is important in the work with RTI systems for a number of reasons. It is needed in order to understand what kind of RTI functions that have a potential to be accepted by the public, and also to get general guidelines for how these functions should work. It is needed in order to adapt the different RTI systems, and the totality of all RTI systems, to the drivers' possibilities and limitations. Finally, it is important in order to assess how the implementation of different RTI systems, and groups of RTI systems, will affect the drivers' behavior.
A logical conclusion from what has been said so far is that more knowledge is needed to answer a large number of questions. On the level of single intelligent helpsystems, more knowledge of cognitive characteristics and learning is needed in order to optimize the information presentation, that is, to improve the drivers' possibilities to perceive, interpret, and understand the messages from the systems. On the level of several interacting intelligent helpsystems, more knowledge is needed concerning the relation between drivers' workload (in terms of static as well as dynamic aspects of different traffic situations) and the helpsystems. This can help identify situations where presentation of extra information should either be avoided, or made in some special way. Such a program needs to test different ways of envisaging the new technology in a realistic context without endangering the traffic situation. For cognitive ergonomic studies, simulations afford a rich source of information.
For attitudinal studies, tossing ideas around and testing their approval among people, video films seem promising. Here, alternative display techniques can be shown in a dynamic traffic setting (cf. Borgström & Svidén, 1990). A video can act as a screening of different display ideas, later to be simulated and tested in dynamic vehicle simulators.
An early testing of the man-machine interaction of drivers and potential IVHS functions and display units is crucial to decide the usability before the costly prototype and field trials stage. If IVHS is to become a blessing to the driver and traffic, a lot of effort is needed to specify the dynamic man-machine interaction between drivers and cognitive IVHS support.