Potential road safety improvements due to Intelligent Road Transportation Systems (IRTS; Advanced Road Traffic Systems in Japan; Intelligent Vehicle-Highway Systems in the United States) are quantified through comparison of road transportation conditions in Japan and the United States. Due to the unavoidable use of numerous assumptions and projections, the results of the quantification exercise are subjective. In spite of this shortcoming, gross-level insights from the exercise indicate that 1) IRTS have the potential of increasing safety, 2) the monetary valuation of the safety benefits potentially gained through IRTS is substantial, and 3) the safety benefits of IRTS increase with diminishing returns over time. More importantly, the process of quantification can be used as an exploratory tool and as a framework for discussing values and negotiating desires. Utilization of the insights gained through this work should prove profitable in guiding safety-related IRTS development and implementation efforts.