Highway collisions are a major source of societal losses, both social and economic. Among the promising approaches to improve highway safety performance is the concept of highway design consistency. Several research efforts have concentrated on translating this concept into quantitative guidelines. However, a number of concerns and challenges in applying the concept and the guidelines still persist and may limit their applicability. Such challenges were identified with the objective of recommending the optimum way to overcome them and establish priorities for future research. The challenges focus on the optimum criteria and parameters to be used in consistency evaluation, models to estimate these parameters, and the relationship between the criteria and safety performance.