2003-01-0954 Safety Belt Fit, Comfort, and Contact ... - Delphi

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All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth Drive Warrendale, PA 15096-0001-USA Email: permissions@sae.org Fax: 724-772-4028 Tel: 724-772-4891 For multiple print copies contact: SAE Customer Service Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-1615 Email: CustomerService@sae.org ISSN 0148-7191 Copyright © 2003 SAE International Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is published in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USA
2003-01-0954 Safety Belt Fit, Comfort, and Contact Pressure Based on Upper Anchorage Location and Seat Back Angle Copyright © 2003 SAE International ABSTRACT A seat belt usability study was conducted to investigate factors associated with seat belt comfort and convenience related to shoulder belt contact pressure, shoulder belt fit, and seat belt upper anchorage location. Two major objectives were addressed in this study: (1) Determine the shift in the contact pressure while changing the seat back angle and seat belt attachment points / B-pillar location by utilizing a body pressure measurement system; (2) Identify how seat belt contact pressure and fit affect users’ subjective feeling of comfort. Results from the statistical analysis shows that the seat belt contact pressure increases when the D-ring moves away from the driver in the fore-aft direction (X-axis) whereas height adjustment of the D-ring (Z-axis) is not statistically significant in terms of pressure distribution. Seat back angle, fore-aft (X-axis) and lateral (Y-axis) positions of the D-ring, and seat belt sub-segments are found to be statistically significant in the analysis of subjective comfort rating for contact pressure, which comply with the results obtained from the statistical analysis of mean contact pressure and distribution. In the analysis of subjective comfort rating on seat belt fit/routing, height adjustment of the D-ring is statistically significant. This indicates that the height adjustment for seat belt upper anchorage point is essential to achieve a better seat belt fit, help reduce the risk of seat belt rubbing the neck or slipping off the occupant’s shoulder, given that it cannot improve the contact comfort by reducing the contact pressure. INTRODUCTION The protection provided to vehicle occupants by the three-point seat belt is no longer disputed over the world. Vehicular seat belts were originally developed to help prevent serious injury to a restrained occupant. Its function is to decelerate the occupant in the vehicle by distributing the forces of collision across the body of the Liang Chen, Rana Balci and Alicia Vertiz Delphi Corporation occupant and by restraining the occupant inside the vehicle during a collision or rollover event. Therefore, increasing the usage rate of the seat belt is a primary goal of all national transport safety policies in motorized countries. Figure 1 shows the seat belt use rates in the U.S. between 1998 and 2001. The average seat belt use rate in the year 2001 reached its all-time high, which is 73%. Year 2001 2000 1999 1998 71% 67% 73% 69% 0% 30% 60% 90% Use Rate (%) Figure 1. Seat Belt Use Rate in U.S. (Source: National Highway Traffic Safety Administration, 2002) To achieve high levels of usage rate, points of concern still are effectiveness, comfort, and convenience, which depend largely on the extent of the geometric design of seat belts matching the occupant’s anatomical characteristics. This study focuses on the comfort and convenience aspects of safety belts from human factors point of view. A number of studies have highlighted potential issues related to the seat belt comfort and convenience (Woodson, et. al., 1980, and Wilcoxon, 1998). A questionnaire administered by Delphi (Balci, et al., 2001) concludes that a primary reason many people give for not wearing a seat belt is that it is inconvenient to be fastened and unfastened and uncomfortable to wear, especially in some specific stature groups, e.g., small females and large males. Therefore, a seat belt usability study was conducted to investigate the factors associated with seat belt comfort and convenience with respect to shoulder belt contact pressure, shoulder belt fit, and seat belt upper anchorage location.
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2003-01-0954 Safety Belt Fit, Comfort, and Contact ... - Delphi

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