Development of a Structural Equation Model for ride comfort of the Korean high-speed railway

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Abstract

This study is aimed at developing a Structural Equation Model for the ride comfort of the high-speed railway launched in South Korea (KTX: The Korea Train eXpress). The Structural Equation Model (SEM) was used to systematically explain passenger ride comfort and quantify the impacts and values of various factors found to be related to the ride comfort of a high-speed train. In order to develop the ride comfort model of the high-speed railway, both the qualitative and quantitative factors were investigated using an on-board passenger questionnaire. The influence of the qualitative factors such as fatigue (physical and visual) and medical symptoms was considered together with various interior design factors such as seat, cabin layout, cabin ambience and tunneling effect. Four hundred and fifty-three subjects participated in an on-board survey. As a result, the proposed SEM model showed statistical significance as well as a high level of model fitness (GFI = 0.928). According to the results, overall ride comfort was significantly affected by the seat-, fatigue- and interior-related variables, as well as customer satisfaction variables. It is expected that the results of this study could be useful for the enhancement of ride comfort in the next generation of the KTX.

Relavance to industry

This study presents a model of ride comfort for high-speed rail. The developed model can be applicable to evaluate overall comfort as well as to quantify the impacts and scores of each qualitative factor on the overall ride comfort of trains or cars.

Introduction

The concept of ride comfort varies depending on time, country, culture and physical condition of passengers. The patterns of train rides have gradually diversified and studies on ride comfort have been progressing in various aspects. However, studies on ride comfort for high-speed trains are relatively rare due to the fact that only four countries, before South Korea, were operating high-speed railways (France: TGV; Spain: AVE; Japan: Sinkansen; and Germany: ICE) with few customer complaints regarding ride quality. The KTX, which operated in South Korea, is the first high-speed train based on the French platform, the TGV. There were some issues raised from passengers who were not familiar with the European style of the cabin interior and the seat design. After a year of the KTX operation, many issues have been raised, all of which can be largely divided into two categories; (1) problems with the rolling stock seat, and (2) problems with the cabin interior (KRRI, 2004). For the rolling stock seat, the major issue was the reduction of an on-time operation ratio due to the frequent occurrence of problems. As for the cabin interior, several issues have been brought up: (1) the negative effect of ride comfort due to the noise generated by many tunnels (specific geological characteristics of the Korean peninsula), (2) the occurrences of motion sickness related to backward seats, (3) the inconveniences related to seats that did not consider the anthropometry of the Korean population, and (4) the inconstant speed (Korail, 2004).

Many studies on ride comfort and seat convenience produced in the past contributed to the improvement of seat design and convenience (Corlett and Bishop, 1976). Branton's (1969) study on ride comfort suggested that ride comfort was related to the deficiency of passengers' experiences or the low quality of seats. Thus, the ride comfort of the seats was evaluated with various methods. These evaluations focused on assessing the degrees of discomfort. Several other studies tried to evaluate positive seat comfort (Zhao and Tang, 1994). Zhang et al. (1996) studied a model for the perception of comfort and discomfort based on the results of Zhao and Tang's study, as well as their own assumption that discomfort was related to the lack of satisfaction from biomechanical factors such as joint angles, muscle contractions and pressure distribution that generates pain, soreness, numbness, and fatigue. On the other hand, comfort was also surveyed to be related to feelings such as relaxation and physical well-being (Metzger, 1994). Peter (2004) conducted a study focused on testing the posture of passengers for cabin design. He evaluated the degree of satisfaction for seat posture with qualitative questionnaires. The results were then implemented in seat designs. Cowings et al. (2001) evaluated the degree to which carsickness affected the performance and emotional state of soldiers during C2V (Command and Control Vehicle) operation. Symptoms that were revealed as hindering factors to ride comfort were drowsiness, headache, nausea, upset stomach, and the effect of the surrounding temperature. In a psychological study related to ride comfort, Looze et al. (2003) analyzed that perceptions of comfort and inconvenience were acquired from the following (including existing information): visual, auditory and olfactory stimuli, current mental status, temperature, moisture, pressure, posture, and movement.

Most of the previous studies demonstrated that ride comfort is a complex emotional state involving various factors such as personal characteristics, hardware design factors, driving environment, etc. It is also important to note that the term ‘ride comfort’ was used synonymously with ‘ride satisfaction,’ ‘seat comfort,’ ‘comfort,’ ‘passenger comfort,’ and ‘ride quality’ (CEN, 1996a, CEN, 1996b, CEN, 1999, ISO 2631-1, 1997, Johan, 2000). In order to minimize confusion with terminology, ride comfort in this study is operationally defined as the state of ‘a pain-free seat environment that is free from physical and visual fatigue to provide a substantial degree of comfort’ (Yun et al., 2004).

There have been a number of studies regarding comfort, ride comfort, ride quality and ride satisfaction for vehicles and transportation systems. However, very few studies have been conducted on the aspects of specific methodologies to quantitatively evaluate ride comfort. Also, previous studies have had some limitations on analyzing ride comfort, a complex concept that includes passengers' subjective sensibilities (passenger fatigue, body status, ride satisfaction, etc.) as well as regional characteristics of the place where the train is running.

Based on this background, it is necessary to develop a quantitative evaluation method that investigates the causality of diverse factors (form of seats, design of compartment, tunnel effect, etc.) related to high-speed train rides. This study proposed an approach to modeling the complex concept of ride comfort. For data collection, this study used an on-board questionnaire on ride comfort (excluding the technical problems of the rolling stock seat). The pilot study examined factors related to ride comfort and the main survey examined the degree of relationship among the factors based on Structural Equation Model (SEM). Finally, this study proposed a model that consists of the examined factors (form of seats, design of compartment, tunnel effect, etc.).

Section snippets

Experiment design

One hundred and seventy-nine and 453 passengers participated in the pilot survey and the main survey, respectively. Table 1 shows the pilot survey and main survey data.

The ambient factors and seat factors were identified by point of view of the cabin design engineers (Korail Co.) and by the results obtained from related studies (Zhang et al., 1996, Johan, 2000, Cowings et al., 2001, Looze et al., 2003, Peter, 2004). Two characteristic variables were added: (1) the tunneling effect that often

Statistical analysis

Based on the results of the survey, the hypothesis was tested by verifying the causalities among each latent variable and executing confirmatory factor analysis. Some cases were determined to be outliers (30 out of 453 cases) and were removed from the group of measurement variables, and the values of measurement variables with different scales were normalized. The outliers were eliminated by the analysis of the univariate outlier and multivariate outlier (Kline, 2005). The outliers were removed

Discussion and conclusion

A SEM technique was used to distinguish variables that affect the ride comfort of high-speed trains directly or indirectly. The results of the analysis, which indicated the suitability of the ride comfort model for each path based on several factors, were significant in the confidence range of 90%. The results of the study also indicated that, in terms of subjective responses, seat pitch, seat width and seat shape (reclining seat) affected the improvement of ride comfort most significantly. The

Acknowledgments

The authors would like to acknowledge the kind support of the KOrea RAILroad (KORAIL) National-2004-425 (the ergonomics study of the ride comfort model development for Korea high-speed rail). This study was jointly funded by KORAIL, KOSEF (KOrea Science and Engineering Foundation), and the Seoul R&BD Program (u-Computing Innovation Center).

References (39)

  • CEN

    Railway Applications: Ride Comfort for Passengers, Measurement and Evaluation

    (1996)
  • CEN

    Railway Applications: Testing for Acceptance of Running Behavior of Railway Vehicles; Part 1: “On-Track” Tests

    (1996)
  • CEN

    Railway Applications – Ride Comfort for Passenger – Measurement and Evaluation

    (1999)
  • Y.H. Chun et al.

    A study on customer satisfaction of sensibility for automotive interior design using structural equation model

    Journal of the Korean Society for Quality Management

    (2000)
  • E.N. Corlett et al.

    A technique for assessing postural discomfort

    Applied Ergonomics

    (1976)
  • R. Cotterill et al.

    The HSE revised fatigue index in the rail industry: from application to understanding

  • P.S. Cowings et al.

    Effects of Command and Control Vehicle (C2V) operational environment on soldier health and performance

    Journal of Human Performance in Extreme Environments

    (2001)
  • J.F. Hair et al.

    Multivariate Data Analysis

    (1998)
  • ISO 2631-1

    Mechanical Vibration and Shock – Evaluation of Human Exposure to Whole-Body Vibrations – Part 1: General Requirements

    (1997)
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