Key Takeaways & Executive Findings
- •• fNIRS provides objective neurophysiological measures of passenger comfort in high-speed railway tunnels, quantifying subjective experiences. • Tunnel passage and sonic booms significantly increase temporal lobe HbO levels (87% and 175% respectively), indicating transient discomfort. • Brain functional connectivity enhances by 52% during tunnel entrance and 80% during sonic booms, reflecting neural responses to environmental stressors. • The study establishes a foundation for evidence-based comfort optimization in railway design using real-time brain imaging.
Abstract
This study innovatively employs functional near-infrared spectroscopy (fNIRS) technology to investigate passengers’ brain responses to various external stimuli during high-speed train operations, assessing their impact on passenger comfort. Three stimuli are examined: passing through tunnels, sonic booms at tunnel exits, and two trains meeting within the tunnel. The analysis of environmental variables, including cabin noise, cabin-to-external pressure, and cabin-to-body acceleration, reveals that changes in auditory and pressure levels during the tunnel experience led to an 87% increase in oxygenated hemoglobin (HbO) levels in the temporal lobe (TL). This reflects a brief discomfort that subsides as passengers adapt, with HbO levels nearly returning to pre-tunnel levels upon exit. Among the stimuli, the sonic boom triggered the most significant neural response, with HbO fluctuations increased by 175%. In contrast, the impact of train meetings was minor, yielding an average HbO increase of only 14.21%. Connectivity analysis further shows significant enhancements in brain functional connectivity during tunnel entrance and sonic boom scenarios, with increases of 52% and 80%, respectively. Our findings contribute to passenger comfort assessment by establishing objective neurophysiological measures that quantify previously subjective experiences. The application of fNIRS in this dynamic environment creates new possibilities for evidence-based comfort optimization in railway design.
1. Introduction
During high-speed train journeys, passengers continuously experience various detrimental factors. These include, but are not limited to, train vibrations, noise, and airflow disturbances [1]. Such vibrations can cause discomfort and fatigue, while the noise might lead to auditory impairments and feelings of oppression. Additionally, disturbances in airflow might trigger pressure imbalances in some passengers’ ears, leading to significant discomfort [2]. Collectively, these factors can reduce the overall comfort experienced throughout the journey. Hence, to address these comfort challenges arising from train travel, it is imperative to monitor, analyze, and assess human comfort during these disturbances and to implement both proactive and reactive measures [3].
Recent studies have increasingly focused on human comfort during train travel, thoroughly examining a range of factors from stress distribution to passenger satisfaction [4]. Notably, comfort is influenced by an interplay of physiological and psychological elements [5], with the properties of seat cushions being identified as particularly crucial in making accurate comfort predictions [6]. Additionally, WU et al [7] innovatively created a 3D model to meticulously analyze ride comfort, while DIACHENKO et al [8] took into account passenger comfort in their design of railway bridge structures. Furthermore, the impact of interior pressure on passengers’ ears [9] and the role of the car body in affecting ride comfort [7] have been subjects of detailed studies. Other recognized factors influencing comfort include noise and vibration [10−12], aerodynamic effects during tunnel passages [13−19], and abnormal train noise, which has been a persistent issue [20]. Meanwhile, cutting-edge technologies, such as machine learning, have been leveraged to enhance safety and comfort in high-speed maritime crafts [21, 22]. Traditionally, comfort evaluation has often relied on theoretical models or post-ride passenger surveys; however, these methods can be highly limited by their subjective nature. In contrast, direct physiological monitoring offers a more objective approach to assessing comfort. For example, electroencephalogram (EEG) technology has been utilized to probe into brain responses and determine comfort levels during train journeys [2]
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LU Jia-hao, WANG Yu-ling, XIAO Yao, NI Yi-qing, AO Wai-kei, CHEN Zheng-wei (2025). Passenger comfort visualized assessment in high-speed railway tunnels using functional near-infrared spectroscopy (fNIRS) brain imaging technology: A full-scale test study. Journal of Central South University. https://doi.org/10.1007/s11771-025-6153-6
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Frequently Asked Questions
What is the main objective of this study?
The study aims to objectively assess passenger comfort in high-speed railway tunnels using functional near-infrared spectroscopy (fNIRS) to measure brain responses to various stimuli such as tunnel passage, sonic booms, and train meetings.
How does fNIRS contribute to comfort assessment?
fNIRS measures changes in oxygenated hemoglobin (HbO) levels in the brain, providing objective neurophysiological data that quantify subjective comfort experiences, unlike traditional survey-based methods.
What were the key findings regarding sonic booms?
Sonic booms triggered the most significant neural response, with HbO fluctuations increasing by 175%, indicating a strong transient discomfort response.
How can these findings be applied in railway design?
The findings provide evidence-based measures that can be used to optimize railway design, such as reducing pressure changes and noise, to enhance passenger comfort.
What is the significance of brain functional connectivity analysis?
The analysis showed significant enhancements in brain functional connectivity during tunnel entrance and sonic boom scenarios (52% and 80% increases), indicating how different brain regions coordinate in response to environmental stressors.
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