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As computer applications for cars emerge, speech-based interfaces provide an obvious alternative to the visually demanding graphical user interfaces common on desktop applications. However, speech-based interfaces may pose cognitive demands that could undermine driving safety. This study uses a car-following task to evaluate how a speech-based e-mail system affects drivers' response to a periodically braking lead vehicle. A baseline condition with no e-mail system was compared to a simple and a complex e-mail system in both simple and complex driving environments. The results show a 30% (310 msec) increase in reaction time when the speech-based system is present. These results suggest several design strategies to mitigate the distraction potential of speech-based systems.

This paper investigates the ride comfort provided by cars equipped with passive and semi-active suspension systems. This investigation is part of a feasibility study for a high speed freeway system for the State of Texas that is proposed for the year 2020. The investigation described in this paper tested two automobiles, one with a passive suspension and one with a semi-active suspension at speeds from 30 mph to 80 mph. The two cars were identical in all other operational aspects except their suspensions. The tests determined the magnitudes of the linear accelerations of the automobiles' front passenger seat for the various testing speeds. These accelerations were converted into a form which could be compared to the International Organization for Standardization (ISO) standards pertaining to the relationship between these accelerations and rider comfort. The ride comfort at 150 mph was predicted from extrapolation of the test data.