This report documents new knowledge of Puget Sound freeway commuter behavior and information needs, relevant to the design and development of a motorist information system for the Seattle area. Methodological innovations resulted in a larger, more relevant sample; more complex and varied data; and a finer grain of analysis than previous efforts to survey motorist behavior. Findings are relevant not only to driver information systems in particular, but also to transportation management in general. Commuters were found not to be a single, homogeneous audience for motorist information, but rather to consist of four subgroups, which we labeled: (1) route changers, (2) non-changers, (3) route and time changers, and (4) pre-trip changers. Commuters were more receptive to motorist information delivered at home than to information delivered on the freeway. Most commuters were inflexible about changing transportation mode, but pre-trip changers were somewhat flexible and more likely to change mode than to change route while on the freeway. The most flexible driving decision was the departure time of route and time changers and pre-trip changers, yet the least flexible driving decision was the departure time of route changers and non-changers. Commuters were fairly flexible to on-road route changes, but less flexible than to changing pre-trip routes based on traffic information received prior to departure. Commercial radio was the preferred medium for on-road traffic information, while HAR and VMS were either not used or not generally perceived as helpful. Whatever the delivery medium, commuters questioned the credibility of motorist information.
The report describes how the identification, analysis, and targeting of susceptible driver groups can improve the design of motorist information systems. Recommendations are also presented to improve commuter response to and use of HAR and VMS.