ITARDA 22th Work Shop Report2019
22nd Presentation Session for Traffic Accident Investigations, Analysis, and Research

Seat belt issues for reducing fatalities and serious injuries of child and elderly passengers

1.

Masanori Taniguchi
Senior Researcher, Research Division

1

ITARDA 22th Work Shop Report

1.

Introduction

The traffic accidents that occurred within Japan in 2018 resulted in 529,378 casualties and 3,532 fatalities. In its
Tenth Traffic Safety Basic Plan, the government set the targets of reducing the number of casualties to 500,000
people or less and the number of fatalities to 2,500 people or less by the year 2020, and it has been promoting avariety of measures to achieve this. As part of this, pedestrians, children, and elderly people, who are referred to as
vulnerable road users, suffer a greater share of damage, and priority initiatives must be taken for them.
Fig. 1 shows the trend in the number of fatally or seriously injured persons per a population of 100,000 people1) by
age group for passengers in the passenger and back seats of the primary and secondary party vehicles for kei, small,and medium sized (passenger) vehicles from the Integrated Database of Traffic Accidents. The number of said
fatally or seriously injured persons has continued to decline across all age groups, which is believed to be amanifestation of the effects of various safety measures.
However, when you view a comparison for each age group, you see that the number of fatally or seriously injured
persons among children between the ages of 6 - 12 and among the elderly age 65 and older has shown less of adecline compared with the cohort of non-elderly people between the ages of 20 - 64. This suggests that the measures
have been slow in reaching them.
120(Only passengers in the passenger / back seats (riding) inkei, small, or medium sized vehicles)

100

Index
指数

80
60
40

Elementary school students: n=2,606
小学生
Non-elderly people: n=36,516
非高齢者
Elderly people: n=22,326
高齢者

20

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

0

Fig. 1. Trends in the number of fatally or seriously injured persons per a population of 100,000 people among
passengers by age group(Number of fatally or seriously injured persons per a population of 100,000 people in 2001 taken to be 100)

Therefore, the actual status of accidents will be investigated in order to contribute to examining future measures forchild passengers between the ages of 6 - 12 and elderly passengers at or above age 65. Since the usage or non-usageof seat belts is profoundly tied to whether or not injuries are sustained during an accident and the severity of said
injuries, in subsequent sections the analysis will be performed by dividing passengers into those who were wearing
and those not wearing their seat belt. The focus of the analysis was placed on fatal and serious injury accidents overa recent ten-year period from 2009 - 2018. Furthermore, since the majority of children between the ages of 6 - 12
are elementary school students, passengers between said ages are referred to below as "elementary school students"
while passengers age 65 and over are referred to as "elderly people." They were compared with non-elderly people
between the ages of 20 - 64 to examine their respective accident characteristics and challenges.

2.

Issues from and an analysis of the non-use of seatbelts

Table 1 shows seat belt usage / non-usage rates for the actual conditions of seat belt use by fatally or seriously
injured persons between the years 2009 - 2018. The definitions for this are provided below. This is a breakdown of2

ITARDA 22th Work Shop Report

the fatal and serious injury accidents, and will vary from the actual usage rate across the market as a whole, including
both accidents involving property damage and accident-free driving.
Usage rate = Number of fatally or seriously injured persons who were wearing their seat's seat belt ÷ Total numberof fatally or seriously injured persons in the passenger and back seats × 100
Non-usage rate = Number of fatally or seriously injured persons who were not wearing their seat's seat belt ÷ Total
number of fatally or seriously injured persons in the passenger and back seats × 100
Table 1. Seat belt non-usage rate for passengers in kei, small, and medium sized (passenger) vehicles when an
accident occurred: 2009 – 2018

Seat belts (total for 2009 - 2018)
Unknown(%)

Total (%)

Elementa
ry school
students

5100

Nonelderly
people3

100

Elderlypeople2100

Non-usage rate (%)

Usage rate (%)

Number of fatally or seriously injured persons (usage, non-usage, unknown) between 2009 - 2018. Elderly people: n=11,447; Nonelderly people: n=12,961; Elementary school students: n=1,100.

Based on Table 1, we can see that the non-usage rate for elementary school students was 5% in the passenger seatand 47% in the back seat for a combined total that is over 50%. When elementary school students ride in a vehicle,
they often have the opportunity to sit in the back seat, and they still have little awareness of wearing their seat beltin the back seat, which is a tendency common to all passengers as a whole. It is conceivably as a result of thesefactors that the share of elementary school students who do not wear their seat belt while riding in the back seat ishigher compared with those of the other age groups at 47%. This non-usage rate of seat belts is thought to be a major
contributing factor behind the delay seen in the decline in the number of fatally or seriously injured persons among
elementary school students.

3.

Issues in wearing one’s seat belt

3-1. Parts of the body where elementary school students sustained injuries
Fig. 2 shows the composition ratio (%) for the parts of the body where fatally or seriously injured persons sustained
injuries when they were wearing / not wearing their seat belt.
Fig. 2 reveals that the share of elementary school students who sustained injuries to their head and face was higher
than that of the other age groups. It is said that children have a greater tendency to tip their upper body forward
during collisions due to the large size of their head as a share of their total body size, as well as their high center ofgravity.2) As such, the assumption is that their head and face frequently come into contact with the interior of thevehicle, causing them to sustain injuries. What is more, with all of the age groups switching from not wearing towearing one's seat belt lessens the share of injuries sustained to the head and face, with the results of wearing thisserving to reduce contact to the head and face.
3

ITARDA 22th Work Shop Report

2009 - 20132014 - 2018

WearingElderly people
Non-elderly
peopleElementary
school sds

100%

50%

Head, face

0% Head, face

0%

50%

100%

Not wearing

Elderly people
Non-elderly
peopleElementary
school sds
Head, face

Neck

Chest, abdomen, andlumbar region

Arms, legs

Other

Fig. 2. Composition rate (%) for parts of the body where fatally or seriously injured persons sustained injuries:
Challenges for elementary school students
Wearing seat belt Elderly people: n=7,632; Non-elderly people: n=8,453; Elementary school students: n=479
Not wearing seat belt Elderly people: n=3,547; Non-elderly people: n=4,141; Elementary school students: n=572

Conversely, insofar as switching from not wearing to wearing one's seat belt reduces the share of injuries sustained
to the head and face for elderly and non-elderly people it has not led to a decrease for elementary school students,
resulting in a widening gap across the age groups. This suggests that elementary school students face issues fromtheir high center of gravity and other issues when it comes to fatalities and serious injuries when they wear theirseat belt.
3-2. Parts of the body where elderly people sustain injuries
Similar to with Fig. 2, based on the composition ratio (%) for the parts of the body where fatally or seriously injured
persons sustained injuries shown in Fig. 3 we can deduce challenges for elderly people.
Fig. 3 reveals that the largest share of injuries sustained by elderly people while wearing their seat belt occur to theirchest, abdomen, and lumbar region, and that the number of said injuries increased from the 2009 - 2013 period to
the 2014 - 2018 period. It has conventionally been claimed that elderly people are at increased risk of bone fracturesdue to a number of factors that accompany aging, such as diminished bone density, reduced flexibility from thecalcification of costal cartilage around the ribs, and alteration of the angle of the rib cage.3) The results of Fig. 3
indicate that elderly people still face challenges in terms of sustaining injuries to their chest, abdomen, and lumbar
region. In addition, while elderly people are at considerably high risk of injuries to this region, elementary school
students and non-elderly people also face a high share of injuries sustained to their chest, abdomen, and lumbar
region, with this trending upward as well. As such, it ought to be kept in mind that this is a challenge facing them
just the same as for elderly people.

4

ITARDA 22th Work Shop Report

2009 - 20132014 - 2018

Chest, abdomen, and lumbar region

Chest, abdomen, and lumbar region

57
Wearing

％

100%

50%

62

Elderly people％Increased

Non-elderly
peopleElementary
school sds

0%

0%

50%

100%

Not wearing

Elderly people
Non-elderly
peopleElementary
school sds
Head, face

Neck

Chest, abdomen, andlumbar region

Arms, legs

Other

Fig. 3. Composition rate (%) for parts of the body where fatally or seriously injured persons sustained injuries:
Challenges for elderly people
Wearing seat belt:
Elderly people: n=7,632; Non-elderly people: n=8,453; Elementary school students: n=479
Not wearing seat belt: Elderly people: n=3,547; Non-elderly people: n=4,141; Elementary school students: n=572

4.

Analysis of wearing one's seat belt: Elementary school students

4-1. Mechanism for injuries as seen from the connection between the parts of the body where elementary
school students sustained injuries and their point of contact with the vehicle
Section 3-1 deduced the challenge that insofar as switching from not wearing to wearing one's seat belt reduces theshare of injuries sustained to the head and face for elderly and non-elderly people, it has not led to a decrease forelementary school students, resulting in a widening gap across the age groups.
When elementary school students and adults are subjected to the same restraining force from their seat belt, theextent to which elementary school students--who have a body weight that is roughly half that of an adult and areshorter in stature as well--come out of their seat due to the impact from the accident is lessened. In addition, there
is not thought to be any difference in the effect from their high center of gravity depending on whether or not they
are wearing their seat belt. Yet despite this, the thinking is that the widening disparity in the share of injuries theysustain to their head and face is potentially a result of the seat belt, which is to say that they are not subject to thesame restraining force as an adult.
This hypothesis will be considered based on the connection between the part of the body where injury was sustained
and the point of contact with the vehicle. Fig. 4 shows the composition rates (%) for the part of the body thatsustained injuries on fatally or seriously injured persons who were wearing their seat belt for both elementary school
students and non-elderly people, and their point of contact with the vehicle. The size of the circles within the figure
express the relative size of this composition rate.

5Exterior part of thevehicle, etc.

Seat, other partof the interior(including seat belt)

Roof

PillarDashboard,door glass

Exterior part of thevehicle, etc.

RoofSeat, other partof the interior(including seat belt)

Injurysustained

PillarPoint ofcontact

Dashboard,door glass

ITARDA 22th Work Shop Report

Head, face
Neck

(1)

(1)

Chest, abdomen,
and lumbar region
Arms, legs
Other

(2)

(2)

[Elementary school students] (100%)[Non-elderly people] (100%)

Fig. 4. Composition rate (%) of injuries sustained by fatally or seriously injured persons wearing their seat belt
and their point of contact with the vehicle: 2009 - 2018
(Total number of fatally or seriously injured persons between 2009 - 2018. Fractions in the first decimal
place were rounded up; 0 was left blank; Only a dot was entered for values between 1 - 5.)
Wearing seat belt Element school students: n=479, Non-elderly people: n=8,453

Fig. 4 (1) reveals that the heads and faces of elementary school students come into contact with a larger number ofparts of the vehicle than do those of non-elderly people. Consequently, this is believed to be because even when
they are wearing their seat belt, when they sustain the impact from an accident their head and face travel a greater
distance than do those of non-elderly people. To put this another way, the extent to which their bodies come out of
their seats tends to be greater than that of non-elderly people.
The points of contact with the vehicle such as the seat and other parts of the vehicle's interior (including the seatbelt) from Fig. 4 (2) indicate that the parts of the bodies where non-elderly people sustain injuries are primarily
concentrated around the neck and the center of the body around the chest, abdomen, and lumbar region. With this,
there is the conceivable possibility that injuries are primarily sustained due to the force from the seat belt itself or
often suffered from rebounding without hitting anything or whiplash from being restrained in the seat by the seatbelt as a result of the restraining effect of the seat belt. Conversely, elementary school students frequently sustain
injuries to their head and face as well as to their arms and legs, which are a slight distance from the center of theirbody. This can be taken to mean that they sustain injuries from contact with the seat and other parts within thevehicle, and that it is relatively rare for them to sustain injuries from the seat belt itself or from being restrained intheir seat by the seat belt.
Based on the above, it is conceivably possible that the restraining force of the seat belt does not exert as much force
on them as it does on adults, as mentioned above.
4-2. Extent of injuries sustained by elementary school students to their chest, abdomen, and lumbar region
and the effects of wearing a seat belt
The extent of injuries sustained to the chest, abdomen, and lumbar region, which is in direct contact with the seatbelt, will be compared for elementary school students and the other age groups to examine the causative factors
producing the different results with the restraining force of the seat belt.

6

ITARDA 22th Work Shop Report

Fig. 5 shows the composition rate (%) for the extent of injuries sustained when the point of contact with the vehicle
is the seat or other part of the vehicle's interior (including the seat belt) from 2009 - 2018.
0%

50%

100%

Elderlypeople
高齢者
Non-elderly
非高齢者
peopleRupture of internal organs

Bone fracture

OthersElementary school小学生
students
Lacerations, abrasions, contusions

SprainsFig. 5. Composition rate (%) for the extent of injuries sustained to the chest, abdomen, and lumbar region fromthe seat or other parts of the vehicle's interior (including the seat belt): 2009 - 2018
Wearing seat belt Elderly people: n=3,717; Non-elderly people: n=3,053; Element school students: n=121

Fig. 5 indicates that just like with elderly people and non-elderly people, with elementary school students bone
fractures account for the greatest share of injuries. But aside from this, lacerations, abrasions, and contusions as wellas ruptures of internal organs account for a roughly two-times greater share with elementary school students as
opposed to with elderly people and non-elderly people, indicating that there is enormous variance in the extent of
the injuries they sustain. From this, it can be surmised that there is potentially variance in where the belt is fastened,
and that it oftentimes may not be fastened properly.
4-3. Manner in which elementary school students wear seat belts while riding in a vehicle
Generally speaking, the claim is made that seat belts are effective for people who are 140cm tall or taller. As
indicated in Fig. 6, the results of a survey revealed that there are various different manners by which child passengers
wear their seat belts while riding in a vehicle. These include cases where they wear them by displacing them due toa sense of discomfort with how the seat belt is supposed to sit due to their neck or the like, wearing them in a position
with poor posture (such as slouched over, etc.), or removing the shoulder strap as a result of the driver maneuvering
to avoid an obstacle.4)-5) There are thought to be numerous cases in which accidents occur under such circumstances
and the victim sustains injuries when their head and face come into contact with parts within the vehicle without
receiving the benefits of wearing a seat belt. This is believed to be one of the reasons behind the delayed reductionin the number of fatally or seriously injured persons who were wearing their seat belt.
(The waist strap was omitted from the diagrams)
Shoulder strap

Worn correctly

Worn in a displacedmannerWorn with poor postureChild shoulder strap
removed due to driver's
steering

Fig. 6. Examples of the manner in which child passengers wear their shoulder strap

7

ITARDA 22th Work Shop Report

In order to obtain the benefits of wearing a seat belt, the seat belt must be properly fastened in place by eliminating
any discomfort from the seat belt and maintaining the proper posture. This is to be done by means of adjusting theheight of the shoulder strap, or by using a booster seat for children 6)-7), which have been proven effective at reducing
the risk of serious injuries in analyses of accidents in the US market.
5.

Analysis of wearing one's seat belt: Elderly people

5-1. Mechanism for injuries as seen from the connection between the parts of the body where elderly people
sustained injuries and their point of contact with the vehicle, as well as the status of the injuries sustained
The large share of injuries sustained by elderly people to their chest, abdomen, and lumbar region was taken up as
an issue in Section 3-2.
Just like with in Chapter 4, a broad view will be taken of the distribution for the composition ratio (%) for the
combined parts of the bodies where injuries were sustained by fatally or seriously injured persons wearing their seat

Exterior part of thevehicle, etc.

Seat, other partof the interior(including seat belt)

Roof

PillarDashboard,door glass

Exterior part of thevehicle, etc.

RoofSeat, other partof the interior(including seat belt)

Injurysustained

PillarPoint ofcontact

Dashboard,door glass

belts among elderly people and non-elderly people, as well as their points of contact with the vehicle, between theyears 2009 - 2018 to consider the factors behind the issue focused on, as indicated in Fig. 7.

Head, face
Neck
Chest, abdomen,
and lumbar region

Arms, legs

(1)

Other

(1)

[Non-elderly people] (100%)[Elderly people] (100%)

Fig. 7. Composition rate (%) of injuries sustained by fatally or seriously injured persons wearing theirseat belt and their point of contact with the vehicle: 2009 - 2018
(Total number of fatally or seriously injured persons between 2009 - 2018. Fractions in the first decimal
place were rounded up; 0 was left blank; Only a dot was entered for values between 1 - 5.)
Wearing seat belt Elderly people: n=7,632; Non-elderly people: n=8,453

Fig. 7 (1) reveals that for injuries sustained by elderly people, the point of contact with the vehicle is concentrated
at the seat and other parts inside the vehicle (including the seat belt). It also revealed that of these, injuries sustained
to the chest, abdomen, and lumbar region accounted for 50% of the total injuries.
Therefore, viewing the extent of injuries sustained by elderly people to their chest, abdomen, and lumbar region by
the seat and other parts inside the vehicle (including the seat belt) shows that bone fractures accounted for morethan 70% of these, as indicated in Fig. 8.

8ITARDA 22th Work Shop Report

100%

50%

0%

0%

50%

100%

Bone fracture
76％

高齢者people
Elderly76％

Non-elderly
非高齢者
peopleElementary
小学生
schoolstudents[2009 - 2013]

Lacerations, abrasions,contusions

Sprains

Rupture ofinternal organs

Other
s

[2014 - 2018]

Fig. 8. Composition rate (%) for the extent of injuries sustained to the chest, abdomen, and lumbar region
from the seat or other parts inside the vehicle (including the seat belt)
2009 - 2013 Elderly people: n=1,838; Non-elderly people: n=1,629; Elementary school students n=50
2014 - 2018 Elderly people: n=1,879; Non-elderly people: n=1,424; Elementary school students n=71

What is more, looking at the types of collisions that caused elderly people to sustain injuries to their chest, abdomen,
and lumbar region due to the seat or other parts inside the vehicle (including the seat belt), reveals that frontal
collisions accounted for 80% of these, as indicated in Fig. 9.
Consequently, it is conceivably possible that these injuries to the chest, abdomen, and lumbar region are sustained
from the restraining force from the seat belt produced when the person's body is thrown forward, which is mainly
seen when frontal collisions occur.
Based on the above, there is the conceivable possibility that the restraining force of the seat belt presents a problem
in terms of injuring elderly people. Presumably, the restraining force of the seat belt will have to be modulated tobe more suitable for elderly people in order to reduce the number of fatally or seriously injured persons.
0%

50%

100%

Frontal collision

Side collision

80％

2014 - 20182014-18年

Rear-end collision

80％

2009 - 20132009-13年

Fig. 9. Composition rate (%) of collision types where injuries were sustained
to the chest, abdomen, and lumbar region
2009 – 2013 Frontal collisions: n=1,156; Side collisions: n=199; Rear-end collisions: n=89
2014 – 2018 Frontal collisions: n=1,116; Side collisions: n=196; Rear-end collisions: n=91
(excluding multivariate collisions)5-2. Actual status of injuries sustained to the chest, abdomen, and lumbar region by elderly people as seenfrom a detailed breakdown by age
The fact that there is an upward trend in the share of injuries sustained to the chest, abdomen, and lumbar region is
one of the issues that was taken up in Section 3-2. This section will analyze elderly people via a detailed breakdownof their ages in five-year intervals to examine the causes for this.
Fig. 10 shows the extent of the changes from the 2014 - 2018 period versus the 2009 - 2013 period regarding the9

ITARDA 22th Work Shop Report

number of fatally or seriously injured persons who sustained injuries to their chest, abdomen, and lumbar region by
a detailed breakdown of the ages of elderly people. The results of this indicate that the number of fatally or seriously
injured persons at or over the age of 80 increased by 111 people. However, since this is conceivably due to theeffects from the rise in the population of elderly people, the extent of the changes in the number of fatally or seriously
injured persons for a population of 100,000 people at or above the age of 80 was ascertained as shown in Fig. 11.
The results of this revealed that while this decreased for people between 80 - 84, it remained largely unchanged for
those between 85 - 89 and increased for people age 90 and over.
Consequently, for people between the ages of 80 - 84, the increase in the number of fatally or seriously injured
persons is thought to have been impacted by the rise in the population within this age group.
As for people between 85 - 89 years old, the number of fatally or seriously injured persons per 100,000 people hasremained largely unchanged in contrast to the inherent assumption that it would decline due to factors like the dropin the number of accidents and improvements in the safety features of the vehicles themselves. For people age 90
and older, both the number of fatally or seriously injured persons and the number of said persons per 100,000 people
have been increasing. For these reasons, conceivable factors behind the increase in the number of fatally or seriously
injured persons among those age 85 and older include the fact that injuries sustained to the chest, abdomen, andlumbar region themselves have increased, with this not just related to the effects of the increase in the population.
It is conceivably possible that the restraining force of the seat belt is a major factor behind the injuries sustained tothe chest, abdomen, and lumbar region, with it within the realm of possibility that the problems from the restraining
force of seat belts are exacerbated among those 85 and older. As the rise in the population of elderly people continues
in the future, the number of fatally or seriously injured persons age 80 and older will continue to increase, just as it
is doing now. This will serve as an inhibiting factor on any declines in the overall number of fatally or seriously
injured persons.

Age (years)

65-69

70-74

75-79

80-84
＋25▲

2014 - 2018

1,442 people

Decrease

Increase

85-89

90-

＋33▲

＋53▲

794 people
+111

-177
2009 - 2013

1,619 people

683 people
Injured part of the body: Chest / abdomen / lumbar region

Fig. 10. Number of fatally or seriously injured persons (number of people)
by a detailed breakdown of ages of elderly people
Wearing seat belt 2009 – 2013 65 -79: n=1,619; 80 and older: n=683 2014 – 2018 65 -79: n=1,442; 80 and older: n=794

10ITARDA 22th Work Shop Report

Decrease

Age (years)

6569

7074

7579

Increase

No change

80-84

85-89

90-

2014 - 20181.20 people

0.81 people

0.46 people

0.26 people

2009 - 20131.50 people

0.92 people

0.48 people

0.19 people

Injured part of the body: Chest / abdomen / lumbar region

Fig. 11. Number of fatally or seriously injured persons (number of people) per a population of 100,000
people by a detailed breakdown of the ages of elderly people
Number of fatally or seriously injured persons per 100,000 people
Age groups between 65 - 79 years old: Number of fatally or seriously injured persons for each age group ÷ Total population between
65 - 79 years old × 100,000
Age groups age 80 and older:
Number of fatally or seriously injured persons ÷ Total population age 80 and older × 100,000

6.

Conclusion

This study analyzed fatal and serious injury accidents among elementary school students (ages 6 - 12) and elderly
people (age 65 and older) from the perspectives of "non-usage" and "usage" of one's seat belt. The following lessons
were learned from the results of this.
Elementary school students: Have a high share of seat belt non-usage.
: Even when they use them, there is still the possibility that they will sustain injuries from fastening theirseat belt incorrectly.
Elderly people: Continue to frequently sustain injuries to their chest, abdomen, and lumbar region.
: The number of fatally or seriously injured persons at or above the age of 80 has been rising. The numberof fatally or seriously injured persons between the ages of 80 - 84 has been rising due to the effects fromthe increase in the population. For people age 85 and older, the problems with the restraining force of
their seat belts is potentially being exacerbated.
: There are concerns that the rise in the population of elderly people in the future will lead to a further
increase in the number of fatally or seriously injured persons.
Responses that will be necessary in the future will be considered below.
Elementary school students: Learn how to correctly fasten their seat belt and soundly put this into practice (guardians).
: Consider measures such as activities to raise awareness of wearing one's seat belt, promote thedissemination of child seats for young children, and make their use mandatory.
Elderly people: Improve the restraining force of seat belts.
: Further promote the dissemination of damage mitigation brakes as a way to reduce the speed at whichcollisions occur.
11

ITARDA 22th Work Shop Report<Reference>
1)

Statistics Bureau of Japan ”Results of the population estimates (2001-018) ”

2）
3)

National consumer affairs center of Japan “Report for child head trauma injuries (1997)”
Koichi Kamiji, et al ”Achievement and effect of safety traffic society for elderly drivers by JAMA ”IATSS
Review Vol.35, No.3 (2011)

4）
5)

Jakobsson.L, et al ”Older children’s sitting posture when riding in the rear seat ”IRCOBI (2011)
Jakobsson.L, et al “Rear seat safety for children aged4-12: Identifying the real-world needs towards
development of countermeasures” 25th Int. ESV Conf., (2017)

6）
7)

Arbogast.K, et al “Belt-positioning booster seats : an update assessment. Pediatrics (2009)”
Anderson.DM, et al “Booster seat effectiveness among older children: Evidence from Washington state”
American journal of Preventive Medicine (2017)12