Design of Minimum Horizontal Curve Radius in Plateau Areas: Psychophysiological Approach

Abstract

The unique natural geographic environment at high altitudes, characterized by low partial pressure, significantly reduces blood oxygen levels and affects human systems. These impacts directly influence drivers’ psychophysiological states, increasing their mental workload and compromising driving safety. Currently, two-lane highways represent the primary type of plateau highways, comprising over 90% of the overall mileage. Therefore, it is essential to examine the minimum radius of the horizontal curve applied to two-lane highways in plateau areas, considering the effects of low atmospheric pressure and hypoxia conditions of plateau areas on drivers. The segments from Nyingchi to the Mountain Shegyla on G318 in the Tibetan plateau region were selected for the field experiment. The model for the simulated experiment was established using the UC/Win-Road software to increase the adequate sample size. The consistency of the field and simulated experiments was validated using the paired sample t-test. Sample entropy is adopted to process the collected multisource data from field and simulation experiments, including the velocity of the vehicles and the heart rate and electroencephalogram of the drivers. Further, principal component analysis was used to evaluate a sample entropy index (SEI), which comprehensively represented the psychophysiological state of drivers. Subsequently, the correlation of SEI with the radius is anatomized, validating that the lateral acceleration ah was the index of most significant influence on SEI from the perspective of driving dynamics. Values of the minimum radius of the horizontal curve for two-lane highways in plateau areas were proposed to amend the current Chinese design specifications for highway alignments. Overall, this research could be essential in alignment design in plateau areas and conspicuously deepens our theoretical and practical understanding of driving safety under low-atmospheric pressure and hypoxia environments.