2021
24th Presentation Session for Traffic Accident Investigations, Analysis, and Research

Analysis of Seat Belt Non-use
Yasushi Nishida
Special Researcher, Research Division11. Introduction
Of the various traffic accident countermeasures that exist, one of the most effective measures for preventing fatal
accidents is a vehicle seat belt.
However, despite the fact that both hardware- and software-based measures have been implemented to get drivers towear seat belts, a joint survey1) conducted by the Japan's National Police Agency and the Japan Automobile Federation(JAF) in 2020 shows that the seat belt non-use rate when driving on general roads was still at 1% and had not reached zero,and that 287 drivers not using seat belts were killed in traffic accidents in 2020 alone. Further improvements to seat belt
use rates are considered indispensable in achieving the goal set forward in the 11th Basic Plan for Traffic Safety of reducing
traffic accident fatalities to 2,000 or less by 2025.
Therefore, to discuss measures aimed at increasing of the seat belt use rate, we analyzed the characteristics of seat belt
non-use using ITARDA's traffic accident database integrated with registered vehicle information and driver databaseintegrated with violation and accident records.

2. Analysis 1: Characteristics of seat belt non-use drivers based on traffic accident data analysis
This section shows the results of three analyses of driver seat belt non-use (seat belt non-use is a violation of laws
requiring the wearing of seat belts) using the traffic accident database integrated with registered vehicle information.
Seat belt non-use rates were calculated with the following formula and data about the seat belt use of not-at-fault drivers(including uninjured parties) of vehicles equipped with a seat belt reminder between 2015 and 2017.
Non-use rate = Number of drivers not wearing seat belts/(Number of drivers wearing seat belts +Number of drivers not wearing seat belts)“Not-at-fault drivers” refers to secondary parties in vehicle-vehicle accidents (the primary party is the driver of thevehicle responsible for the initial collision) who
did not violate laws and were not involved in aof general drivers.

Information for ages 95 andabove is not shown due toinsufficient data

All agessuch drivers are considered to be similar to those

19 and under
20~24
25~29
30~34
35~39
40~44
45~49
50~54
55~59
60~64
65~69
70~74
75~79
80~84
85~89
90~94

driving method or manner. The characteristics ofSeat belt non-use rate (%)

traffic accident due to factors such as theirFig. 1 - Driver seat belt non-use rate by age group(Seat belt non-use rates were calculated based on seat belt usage

between 2015 and 2017 by not-at-fault drivers of vehicle models
for which seat belt reminder equipment has been required since2005)
2

2-1. Age and seat belt non-use rates
Figure 1 shows seat belt non-use rates by driver age group. The seat belt non-use rate for all age groups is 1.1% and isalmost the same level as the 1% from the National Police Agency/JAF Joint Survey1), meaning this method of calculating
seat belt non-use rates used is considered to be appropriate. Seat belt non-use rates for drivers aged from 19 to their early
30s is high at approximately 1.4%, before decreasing with age from the late 30s. Although rates remain low at 0.8% or lessfrom the late 50s until the early 70s (hereinafter, "middle age"), rates rise again from the late 70s and exceed 0.95% at 75
and above.

2-2. Vehicle model year and seat belt non-use rates
The equipping of a seat belt reminder which warns a driver to wear a seat belt when driving via displays or sounds
became obligatory in September 2005.
effectiveness of this device by classifying
vehicles newly registered from 2006
onwards and equipped with such devices
as “new type model vehicles” andvehicles registered in 2005 and earlier andwithout such devices as “old model

Seat belt non-use rate (%)

With this in mind, we examined theby examining seat belt non-use rates by
age group and vehicle model year, wewere able to confirm that seat belt
reminders were effective due to the low

All ages

vehicle model year were low at 0.5 to 1%,

19 and under
20~24
25~29
30~34
35~39
40~44
45~49
50~54
55~59
60~64
65~69
70~74
75~79
80~84
85~89
90~94

vehicles”. Although differences due toFig. 2 - Trends in driver seat belt non-use rate by age group and year
(The rates were calculated by seat belt use condition of not-at-fault drivers of model
vehicles, those have been targeted for seat belt reminder equipment since 2005)

rates of seat belt non-use by drivers of
new type model vehicles across all age groups. (This figure was not shown in this paper, but is shown as Fig. 4 in the Power
Point file from the presentation session.) However, when looking at the relationship between the prevalence of vehicles
equipped with seat belt reminders and seat belt non-use rates, although diffusion rates of new type model vehicles in eachperiod as shown in the legend of Fig. 2 have increased from 12.6% in 2006-2009 to 84.3% in 2018-2020, there have been
almost no recent decreases in seat belt non-use rates. In other words, the spread of warning systems (seat belt reminders)has not had any additional effects in terms of further decreases in seat belt non-use rates.

3. Analysis 2: Characteristics of seat belt non-use drivers based on traffic violation data analysis
This section shows the results of analysis performed on the relationship between age and citations for traffic violations
including seat belt non-use (such non-use is a violation of laws requiring the wearing of seat belts) using ITARDA's
integrated driver database with traffic accident/violation records that includes the violation data of 91 million drivers
throughout Japan.

33-1. Repeated violator of road traffic law
Figure 3 shows how many drivers have
Excessive speed

Seat belt non-use

been cited for traffic violations, including seatbelt non-use using percentages of licensed

Citation percentage (%)

drivers cited over the past three years(hereinafter, "percentage of drivers cited") by
age group. The types of traffic violations with

Failure to stop at
stop sign

85~89

80~84

75~79

70~74

65~69

60~64

55~59

50~54

45~49

40~44

35~39

30~34

25~29

All ages

Driving into areas wheretraffic is prohibited

Mobile phone

20~24high percentage of drivers cited differ by age

traffic

90~94

Ignoring
signalFig. 3 - Percentages of drivers cited by violation type and age group(The data was calculated targeting at drivers cited between 2015 and 2017. Divers
were not necessarily cited by one type of violation. Ages are as of the end of 2018.)

group. In the 25~29 age group, the percentage
of drivers cited for excessive speed (▲) is
high, and nearly 8% of licensed drivers havebeen cited over the past three years. Youngpeople are also often cited for mobile phone
usage (◆), with percentages decreasing withage in the same manner as excessive speed
violations. Ignoring traffic signals (■) anddriving into areas where traffic is prohibited (■) gradually decrease as drivers after drivers pass 80 years in age. One
violation for which there is little change in the percentage of drivers cited depending on the age group is failing to stop at
stop signs (▲), which peaks at the late 40s and trends at approximately 4% from the 50s until the 70s. Among violations,citations for seat belt non-use (●) gradually decrease from the late 20s, but again increase from around the 60s, resulting in
the largest difference with other types of violations.
Among drivers cited for traffic violations, some drivers repeat the same violation after being cited, while others learn
from their citation and modify their behavior and awareness accordingly to avoid being cited again. Also, the types ofviolations for which drivers are most often cited are not necessarily those for which drivers are most often cited repeatedly.
In order to study which types of violations
drivers tend to be cited repeatedly, Figure 4

Percentage of recidivists (%)

Mobile phoneshows the percentage of recidivists (drivers
cited for violations two times or more) among

Seat belt non-use

the number of drivers in each age group cited

Excessive speed

for violations over the past three years.

Failure to stop at stop sign

Although the relationship between age andthe percentage of recidivists depending on the

Driving into areas wheretraffic is prohibited

Ignoring traffic signal

violation type is similar in some ways to
90~94

85~89

80~84

75~79

70~74

65~69

60~64

55~59

50~54

45~49

40~44

for excessive speed (▲). For drivers in their

35~39

recidivists for mobile phone usage (◆) than

30~34

Fig. 4 - Percentages of recidivists by violation type and age group(The data was calculated by targeting drivers cited between 2015 and 2017. Drivers
were not necessarily cited for just one type of violation. Ages are as of the end of
2018.)

25~29

percentages is very different. Among young

20~24

All ages

driver citation rates, the ranking of these4people, there is a higher percentage of

60s and 70s, although the percentage ofdrivers cited for failing to stop at stop signs (▲) is high, seat belt non-use (●) has a higher percentage of recidivists. Because
drivers aged 60 and older have the highest percentage of seat belt non-use, seat belt non-use is a behavior for which
preventing repeated citations by modifying one's behavior or awareness characteristics may be difficult for the elderly.

3-2. Traffic violations and behavioral characteristics
In general, people behave to avoid repeating failures. Furthermore, the majority of people cited for traffic violations
change their method of driving or their awareness regarding traffic safety to prevent being cited for traffic violations again(particularly for the same type of traffic violation). In other words, they modify their behavioral characteristics.
Therefore, if behavioral characteristics are successfully corrected, the percentages of recidivists cited repeatedly for thesame type of violation and in the same region (prefecture of residence) in a short period of time will decrease. Conversely,
if the percentage of recidivists does not decrease, it is assumed that the ability of drivers to correct their methods andFirst-time offenders

correct such behavioral characteristics that we

Failing to stop at
stop sign

analyzed the percentage of recidivists who did

Ignoring traffic
signalExcessive speed
Driving into areas wheretraffic is prohibited

Recidivists (citations within 3
years prior and 1 or 2 years prior)

All ages

perspective of an impaired driver ability to

Seat belt non-use

Mobile phone

20~24
25~29
30~34
35~39
40~44
45~49
50~54
55~59
60~64
65~69
70~74
75~79
80~84
85 and above

Percentage of citations in prefecture of residence (%)

awareness has become impaired. It is from thisnot use seat belts.
Figure 5 shows percentages of drivers cited
for seat belt non-use in their local area
(prefecture of residence) by age group.

Seat belt non-use
Failing to stop at
stop sign

Although it is thought that drivers will have

Mobile phonedecreased rates of repeated citations for the

Ignoring traffic
signalExcessive speed
Driving into areas wheretraffic is prohibitedsame violation in their local area if they modify
theirbehavioral

comparing

Fig. 5 - Citation percentages in the prefecture of residence by first time
offenders (2015) and recidivists (drivers cited by the same type of violation in2015 and 2016 or 2017) by violation type and age group(The data was calculated by targeting drivers cited between 2015 and 2017. Drivers were
not necessarily cited for just one type of violation. Ages are as of the end of 2018.)

citationcharacteristics,
percentages

when
in

the

prefecture of residence from three years ago (○)
with citation percentages in the prefecture ofresidence from two years later (●), thepercentage from later (●) is high, meaning it
may be difficult for the behavior of drivers who
do not wear seat belts to be modified.

Failing to stop at stop signs differs from seat belt non-use in that the percentage from later (▲) is lower than thepercentage from three years ago (△), meaning it is possible that behavior or awareness were modified. The same trends as
seen for failing to stop at stop signs can also be seen for mobile phone usage (◇, ◆), ignoring traffic signals (□, ■),excessive speed (△, ▲), and driving into areas where traffic is prohibited (□, ■).
In the case of first-time offenders, as with recidivists, the older the driver is, the higher of the percentage of citation in
the prefecture of residence is. It is thought this is due reductions in peoples’ range of behavior that often comes with aging.
54. Analysis 3: Relationship between
violation/accident experience and seat
Seat belt non-use rate (%)

belt non-use
discussed both seat belt non-use whiledriving and citation characteristics, but inthis section, we will show the results of theanalysis on relationships between the two

Violation
No violation
Seat belt non-use
No seat belt non-use

20~24
25~29
30~34
35~39
40~44
45~49
50~54
55~59
60~64
65~69
70~74
75~79
80~84
85~89
90~94

variables.

All conditions

4-1. Violation/accident experience andseat belt non-use
Figure 6 shows seat belt non-use rates
among drivers cited for several types of

All ages

Up to this point, we have separately

Fig. 6 - Seat belt non-use rate by three-year violation record and age group(Data was calculated by targeting at not-at-fault drivers of semi-large/medium/small
sized passenger vehicles or medium/small sized goods vehicles in 2018, with the threeyear violation record spanning from 2015 to 2017)

violations. More specifically, it shows seatbelt non-use by drivers with and without a citation record for seat belt non-use or other violation over the past three years
by age group, as well as that of not-at-fault drivers.
In each age group, the percentage of drivers with a record of citation for seat belt non-use (●) was the highest, and it isassumed that many of the drivers cited for seat belt non-use will continue to drive without wearing a seat belt in the future
as well. However, age groups 65~69 to 80~84 are at the same level regardless of violation record (▲, △), and thecharacteristics associated with traffic violation behavior may change in these age groups.
4-2. Seat belt non-use andaccident rates
Table

1

Table 1 - Accident driver ratio and quasi-induced exposure ratio by age group and number ofcitations for seat belt non-use over the past three years(In 2018, with three-year violation records spanning from 2015 to 2017)shows

Accident driver ratio (%)

subsequent accident rates

No. of citations

and driving frequency ofdrivers cited for seat belt
non-use by age group. As
indicators
rates

for

accident

anddriving

frequency,

we

used

accident driver ratio andquasi-induced

exposure

ratio as shown below.
Accident driver ratio:

Quasi-induced exposure ratio (%)

Noviolations

1 time2 time3 time

20~24
25~29
30~34
35~39
40~44
45~49
50~54
55~59
60~64
65~69
70~74
75~79
80~84
85 and above
All ages

Percentage of drivers who
were a primary party in a traffic accident during 2018 (%)
6

4 timeNo. of citations
5 or more
times

Total

No
violations

1 time2 time3 time4 time5 or more
times

Total

(Number of drivers who were a primary party in a traffic accident/Number of all drivers)
Quasi-induced exposure ratio: Percentage of drivers who were not-at-fault drivers in a traffic accident during 2018 (%)(Number of not-at-fault drivers/Number of all drivers)
Across all age groups, the driving frequencies of drivers cited for seat belt non-use was higher than that of those drivers
not cited, with those having more citations also having higher driving frequencies. The same trend can also be seen in theratio of drivers who were a primary party in an accident, meaning that drivers cited for seat belt non-use can be considered
drivers at a high risk of being involved in traffic accidents.

5. Discussion
5-1. Psychological characteristics of drivers who do not wear seat belts
According to the material on accidents involving novice drivers and their violation characteristics2), rates of newly
licensed drivers being cited for seat belt non-use (this rate takes driving frequency into consideration) decrease over timeor as these drivers accumulate driving experience. From this, it is conceivable that the reason for high seat belt non-use
rates among young people is that because they have no driving experience, they do not sufficiently understand theimportance and usefulness of knowledge acquired during classroom lectures. Considering the fact that drivers who will
potentially wear a seat belt have the characteristic of decreased seat belt non-use rates as they accumulate driving experience,
it is conceivable that proactive measures such as public relations or public awareness campaigns would prove effective at
encouraging novice drivers to accumulate driving experience in a short period of time and would have the same sort ofeffects as on-the-job training.
On the other hand, associations between impaired cognitive function and seat belt non-use as shown in the material3)
indicate that aging-related impairment of cognitive functions may be the cause for high seat belt non-use rates among theelderly. For this reason, instead of conventional measures that employ public relations, public awareness, or education, it
may be necessary to consider measures from a medical perspective, which can be significantly more difficult to implement
than measures employed for young people.
Because the above observations are based on limited analysis results, multifaceted analysis, such as of the psychologicalcharacteristics of drivers who do not wear seat belts, is required in order to enable more rigorous observations to be obtained
and measures for increasing seat belt use rates.
5-2. Traffic violation behavior and traffic accident risk
Because traffic accidents are often caused by traffic violations such as excessive speed and driving into areas wheretraffic is prohibited, traffic control, traffic guidance, and traffic safety education are implemented from the perspective ofpreventing traffic accidents.
On the other hand, although many materials discuss how seat belts are effective in reducing injury in the event of a traffic
accident, or how they enable drivers to maintain proper driving posture and in turn reduce fatigue and prevent operational
errors, there are almost no instances of quantitative discussions highlighting the fact that drivers who do not wear seat belts
are more likely to cause an accident.
The results in Table 1 show that drivers who do not wear seat belts are more likely to be involved in an accident. However,7

when calculating the accident rate per unit of driving frequency (estimated using the values from Table 3 and the formula"relative accident ratio = parties concerned in accident / quasi-induced exposure ratio"), despite there being somedifferences depending on driver age, the difference in rate depending on number of citations is low. This fact means that adriver who has a large number of citations is not necessarily a driver whose method of driving is problematic (risky).
Therefore, the reason why the accidents shown on the left side of Table 3 are more likely to occur is because the drivers
with large numbers of citations shown on the right side of Table 3 have a higher driving frequency.
When studying measures for preventing accidents by drivers with a large number of citations for seat belt non-use, thefact that "drivers with high driving frequencies have a higher rate of accidents during a certain period of time", which is
generally true for drivers cited for traffic violations, should be taken into consideration. This does not mean that "accidents
are unavoidable because a driver's driving frequency is high", but instead that "because these drivers drive three times more
often than other drivers, they need to be three times more careful than others when driving".

6. Conclusion

6-1 Summary of the analysis
Below is a summary of the analysis introduced in this paper.
Analysis 1: Characteristics of drivers who do not wear seat belts (based on traffic accident data analysis)● Seat belt non-use rates are high for young people (under 50) and for the elderly (75 and older).
● Seat belt non-use rates are high for young people (under 50) in prefectures other than their prefecture of residence,and for the elderly (75 and older) in their prefecture of residence.
● Although seat belt reminders are effective, they have a minimal effect on increasing seat belt non-use rates.
Analysis 2: Characteristics of violators who repeat seat belt non-use (based on traffic violation data analysis)● The relationship between percentages of drivers cited for seat belt non-use by age group (licensed drivers who
have received a citation over a three-year period) and percentages of recidivists (drivers who have received two or
more citations over a three-year period) varies by violation type.
● Seat belt non-use is a behavior that is difficult to modify for all age groups.
Analysis 3: Relationship between traffic violation/accident and seat belt non-use (based on traffic violation/accident data
analysis)● Seat belt non-use rates are high among drivers with a history of accidents and violations, and lowest among drivers
with no history of accidents and violations (for almost every age group).
● Drivers and recidivists cited for seat belt non-use have a high rate of subsequent accidents.

86-2. Future utilization
From this research, we propose new ways of utilizing the integrated driver database with traffic accident/violation records.
(1) Analysis of non-accident drivers for accident prevention
If our target is a society without traffic accidents, it is necessary to study not only accident cases but also non-accident
cases. Concerning this point, traffic accident data analysis can only provide us with information on drivers involved in
accidents, but not that of drivers not involved in accidents. However, the proposed integrated driver database with traffic
accident/violation records can provide both these types of information. Furthermore, a comparison study that shows thecharacteristics of both drivers involved in accidents and those not involved in accidents is expected to make safety driver
education more effective.
(2) Systematical analysis of the effect of traffic enforcement
The effects of traffic enforcement are not always same and they sometimes appear in the short-term or long-term, or overa limited area or wide area due to the variety of methods and target groups analyzed.
Most studies on what effects traffic enforcement has on accident prevention are based on limited areas or methods,
making it difficult to systematically discuss effects in terms of time and spatial points of view.
One reason for these difficulties is a lack of data to enable such systematic discussions.
The integrated database, which contains traffic violation data for all Japanese drivers (type of violation, scene, date, etc.)from over the past 20 years, as well as traffic accident data (type of collision, scene, date, etc.), makes it possible to discuss
this topic from both time and spatial points of view.

<References/Sources>(1) Joint survey by the National Police Agency (Japan) and Japan Automobile Federation (JAF)
https://jaf.or.jp/common/safety-drive/library/survey-report/2020-seatbelt(2) Y. Nishida; The novice driver’s characteristics of traffic accidents/violations, Jidousha-Gakkou 57-99, 38-44(2021)<in Japanese>(3) Y. Nishida; Relationship between seat belt non-use and cognitive decline, Gekkan-Koutsu 52-9, 68-75(2021) <inJapanese>9