Considerable debate has focused on the safety of commercial heavy trucks, and particularly on the question of whether allowing truck sizes and weights to increase would degrade safety. Efforts to answer that question have centered on two approaches, crash data analyses and, comparative analyses of the safety-related engineering performance capabilities of various truck configurations. This paper summarizes recent crash data analysis work, while a companion paper to this one, (“Vehicle Stability and Control Research in the U.S. Comprehensive Truck Size and Weight Study, SAE Paper No.
982819), addresses what can be learned from engineering analysis of this issue. Together, these two approaches yield insights into the potential safety outcomes that could result if truck size and weights requirements were changed. Some outcomes might not be positive. This paper concludes with a discussion of the conditions under which positive outcomes might be possible.