Interface pressure data and the prediction of driver discomfort in road trials

doi:10.1016/S0003-6870(03)00009-7

Applied Ergonomics

Volume 34, Issue 3, May 2003, Pages 207-214

https://doi.org/10.1016/S0003-6870(03)00009-7 Get rights and content

Abstract

An objective measure that will predict discomfort reliably, and which can be used at an early stage in the development of a vehicle and its seating, would have the potential to reduce the prevalence of musculoskeletal problems associated with driving. This paper reports on an extended road trial study to further investigate the potential value of pressure distribution data in the prediction of reported discomfort. Road trial data were collected from three cars and then interface pressure data were recorded for each of the three seats. Clear differences were identified between the cars with respect to reports of discomfort. However, no clear relationship was found between interface pressure data and reported discomfort.

Introduction

The Vehicle Ergonomics Group (VEG) has evaluated over 100 vehicles since 1981 and has established methods of collecting mainly subjective data for evaluating the driving workstation during extended road trials. Whilst these data are of high quality, it is a lengthy process, sometimes taking several months to complete and it is often carried out at a late stage in the vehicle's development when the car is a pre-production prototype or already in production (Porter, 1995). An accurate method for predicting body area discomfort, and consequently assessing the quality of the seat and driving package, would have a major advantage of providing rapid information which could be used early on in the design process.

There is potential for seated pressure distribution to be used as a predictor of discomfort. For example, the tissues covering the IT can be subjected to extremely high pressures during sitting that are sufficient to reduce blood circulation through the capillaries. If there is no readjustment of body position, then metabolite build up and the symptoms of aches, pain, discomfort and numbness occur. It then seems logical in any seating design that areas of high pressure should be minimised and pressure optimally distributed across the sitting region. Car manufacturers are already interested in using interface pressure measurement as a technique for predicting discomfort (e.g. Lee and Ferraiuolo, 1993; Gross et al., 1994; Thakurta et al., 1995).

The literature attempting to correlate discomfort with interface pressure data is not extensive, is of limited value and is discussed in a previous paper (Gyi and Porter, 1999). The conclusions are generally contradictory and often based on short duration trials of 5, 10 or 15 min (e.g. Gross et al., 1994; Lee and Ferraiuolo, 1993; Shen and Galer, 1993), such that further exploration of the technique is clearly required. Earlier research on interface pressure measurement carried out by the authors (Gyi et al., 1998; Gyi and Porter, 1999) has not shown a clear relationship between discomfort and interface pressure data, based on data from 2.5 h laboratory ‘driving trials’ controlling for either seat design or posture.

This paper describes an extended road-trial study to further investigate the potential value of pressure distribution data in the prediction of reported discomfort. Three cars were used in the road trials study (one prototype and two production models from competitor manufacturers).

Section snippets

Participant selection

A sample of 18 drivers, eight male and 10 females, was carefully selected from the British public to include a wide range of body sizes (Fig. 1). Individuals were chosen initially by height, and then the sample was refined to produce a good range across percentiles for both males and females in the other six anthropometric variables measured. Driving licenses were checked and prospective subjects took a 15 min ‘test drive’ accompanied by the experimenter. Drivers who were nervous or experienced

Reported discomfort

Friedman's two-way Analysis of Variance (ANOVA) by ranks was calculated from the road trial discomfort data at each of the five time periods. Cochran's Q test was applied to the same data converted to dichotomous form (discomfort/no discomfort). Discomfort was clearly observed to increase over time, for example, the back, buttocks and thighs as illustrated in Fig. 2. Table 1 shows the body areas with significant differences in discomfort between the cars. Car C received the highest percentage

Discussion

There was strong agreement amongst the subjects that Car C was the most uncomfortable of the three cars when considering buttock, thigh and back discomfort. Fig. 2, Fig. 3 clearly expose this car as a potential ‘health hazard’ given the level of reported discomfort in comparison to the other two cars. Car C was not the prototype car, but had been in production for several years. It would be of considerable interest to interview long-term owners of these cars to assess whether owners of Car C

Conclusions

This research has confirmed that the simple quantification of static seat interface pressure data from a variety of individuals, with the assumption that high (or low) pressure values are predictors of reported discomfort during an extended drive, is unsatisfactory. It thereby supports the conclusion of the previously reported laboratory-based study (Gyi and Porter, 1999).

As driver discomfort is a dynamic phenomenon, it is recommended that dynamic data are captured regarding changes over time

Acknowledgements

The authors would like to acknowledge the Brite-Euram European Initiative (Project 5547) for funding this research. The authors would also like to thank Novel_gmbh for the loan of the Pliance system for the purpose of this work.

References (14)

D.E. Gyi et al.
Interface pressure and the prediction of car seat discomfort
Appl. Ergon.
(1999)
D.E. Gyi et al.
Seat pressure measurement technologiesconsiderations for their evaluation
Appl. Ergon.
(1998)
V. Bhatnager et al.
Posture, postural discomfort and performance
Hum. Factors
(1985)
R.S. Bridger
Postural adaptions to a sloping chair and worksurface
Hum. Factors
(1998)
E. Grandjean et al.
VDT workstation designpreferred settings and their effects
Hum Factors
(1983)
C.M. Gross et al.
Lee, J., Ferraiuolo, P., 1993. Seat comfort, S.A.E. Technical Paper No....

There are more references available in the full text version of this article.

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¹: Department of Human Sciences, Loughborough University, UK.

View full text

Interface pressure data and the prediction of driver discomfort in road trials

Abstract

Introduction

Section snippets

Participant selection

Reported discomfort

Discussion

Conclusions

Acknowledgements

Appl. Ergon.

Appl. Ergon.

Posture, postural discomfort and performance

Hum. Factors

Postural adaptions to a sloping chair and worksurface

Hum. Factors

VDT workstation designpreferred settings and their effects

Hum Factors