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

Mean Pressure (g/cm2)
.09
.08
.07
.06
.05
.04
.03
1.00
2.00
3.00
4.00
5.00
Seat Belt Segments
6.00
7.00
8.00
D-ring in Y-axis
Inside
Middle
Outside
Figure 5. Mean Pressure Distribution as a Function of
"D"-ring Location in Inboard-Outboard Direction
Mean Pressure (g/cm2)
.08
.07
.06
.05
.04
.03
Inside
Middle
D-ring in Y-axis
Outside
D-ring in X-axis
Foremost
Middle
Rearmost
Figure 6. Mean Pressure Distribution as a Function of
"D"-ring Locations in Both Fore-Aft and Inboard-Outboard
Directions.
SUBJECTIVE RATING ON CONTACT PRESSURE AND
SEAT BELT FIT
ANOVA on subjective rating of contact pressure (see
Appendix ANOVA Table 4) shows that the seat back
angle, D-ring location in both fore-aft and inboardoutboard
directions are still statistically significant. This
outcome complies with the results from the ANOVA on
objective measurements of contact pressure and
distribution. Conversely, the D-ring location in height
adjustment is not a significant factor, which means that it
has a little impact on sensed seat belt pressure in terms
of occupant’s subjective feeling. However, in ANOVA on
subjective rating regarding seat belt fit/routing; all of the
4
variables, including seat back angle, D-ring in fore-aft,
lateral, and vertical directions, are statistically significant.
This finding indicates that the height adjustment for seat
belt upper attachment point is essential to achieve a better
seat belt fit/routing and to help reduce the risk of seat belt
rubbing the neck or slipping off the occupant’s shoulder.
However, it cannot improve the contact comfort by
reducing the contact pressure. Figure 7 displays the
mean value/ trend of occupants’ comfort rating on seat
belt fit with respect to the seat back angle and D-ring
location on Z-axis. There is a significant difference in
comfort rating for different levels of D-ring height, which
support the results from ANOVA table (Table 4 in
Appendix).
As a general observation from the experiment, some
participants who were in the low height and low BMI
category complained about the seat belt rubbing their
necks. Although it cannot be generalized due to the small
number of participants, a similar complaint was received
from the participants who were at the higher end of the
BMI and height scale combination.
Mean Pressure (g/cm2)
2.8
2.6
2.4
2.2
2.0
1.8
0 degree
10 degree
Seat Back Angle
20 degree
D-ring in Z-axis
Figure 7. Subjective Rating on Seat Belt Fit as a
Function of Seat Back Angle and "D"-ring Locations in
Different Height Levels
Note: Comfort Rating Scale (1-5)
1: Slipping off the shoulder
3: Just right
5: Rubbing the neck
DISCUSSION
In this study, height and BMI data of all participants were
recorded as the between-subject variables. However, the
results of ANOVA with repeated measurements for each
participant show that body height and BMI are not
statistically significant. Hypothetically, body height and
High
Low