Traditional road geometric design is based on assumptions regarding human perception and reaction, which directly influences Stopping Sight Distance (SSD) and the associated design parameters of vertical curves. Under a future scenario of full autonomous vehicle (AV) deployment, reduced perception–reaction times and modified sensing configurations may change visibility-controlled design requirements. This study presents a structured parametric assessment of SSD and vertical curve lengths under the assumption of full AV operation. Variations are considered in reaction time, sensor height, sensor inclination angle, longitudinal grade, and vehicle operating speed. Default parameter values derived from current design standards, together with ranges reported in the literature, are used to evaluate the geometric implications of full vehicle automation within a controlled analytical framework. The results indicate that reduced reaction times and increased sensor heights of AVs may decrease required SSD values and consequently shorten crest and sag vertical curve lengths compared to conventional human-driven vehicle assumptions. For sag curves in particular, headlight inclination angle is revealed as a significant geometric variable. Overall, the study proposes a framework for examining the interaction between AV sensing characteristics and vertical geometric design, thereby providing a basis for future evaluation of design standards without directly prescribing modifications to current practice.
Maria Pomoni (Tue,) studied this question.