No.126■ For road environments:
The expectation is that thorough maintenance and management will be carried out for center lines
and road shoulders of major roadways, since uneven surface conditions prevent drivers fromdeviating from their lanes and will boost detection by vehicles with onboard cameras.

渉外事業課

TEL 03-5577-3973

FAX 03-5577-3980

公益財団法人 交通事故総合分析センター●ウェブサイト http://www.itarda.or.jp/ ●Eメール koho@itarda.or.jp●フェイスブック https://www.facebook.com/itarda.or
本部〒101-0064 東京都千代田区神田猿楽町2-7-8 住友水道橋ビル8階
TEL 03-5577-3977(代表) FAX 03-5577-3980

ITARDA INFORMATION no.126

つくば 交通事故調査事務所

住 友 水 道 橋 ビル８ 階

イタルダインフォメーションに関するお問い合せ先

交通事故分析レポート No.126
Fatal accidents caused by later-stageelderly people driving kei-passenger carslSpeciafeature~ Be careful of lane departures on main roadways! ~200

About 2.3-fold
Medium-sized
passenger cars

4since 2007

150

3
Kei-trucks

1002

Kei-passenger cars
50

1

0

Number of kei-passenger cars owned(10 million vehicles)

参 考文 献1) 日本自動車工業会：自動車保有台 数 統 計 資 料2) 日本自動車工業会：「2015年度 軽自動車の 使 用実態 調 査 報 告書」, 2016年 3月
3) 寒 地土木研究 所 平澤 他：「新しい事故 対 策手法としてのランブルストリップスの開発と実 用化に関する研究」，
土木学 会論文集 第４部門 NO.800 / Ⅳ−69，2005年10月．
4) 国土 交 通省：ASV技術普及状 況 調 査 資 料
5) ITARDA 三枝：「軽 乗 用車運 転中の 後 期高齢 者による死亡事故の 特 徴と対 策」,設 立25周年記 念フォーラム論文, 2017年10月

3〒101 0064 東 京 都 千 代 田 区 神 田 猿 楽 町 ２ ７ ８(Tatsuhiko Saegusa)

30

公益財団法人 交通事故総合分析センター■ In conclusion
Kei-passenger cars play an indispensable role as an important means of transportation that offers analternative to local public transportation for elderly people. In aiming to further reduce the number offatal accidents among such drivers, it is not enough to just rely on improvements to the collision safetyof vehicles. Rather, initiatives to popularize and advance preventative safety technology (includingthat for infrastructure), as well as those for integrated safety on the part of society as a whole(including post-accident care) are growing increasingly important. The expectation is that safety will
be further enhanced by actually promoting such initiatives.

ITARDA INFORMATION

Number of fatal accidents (accidents)

交通事故分析レポート■ For driving awareness by elderly drivers:
Aimless driving results in the occurrence of a great many head-on collision accidents. Elderly drivers
are encouraged to reaffirm the risk of head-on collisions on roads with oncoming traffic, and shouldmake efforts to drive by focusing their attention even when driving on familiar roads during thedaytime.

This analysis revealed that countermeasures against head-on collision accidents involving
kei-passenger cars, especially preventing deviations from one’s lane, are important for the sake of
reducing the number of fatal accidents caused by later-stage elderly drivers. As such, expectations
regarding ways to achieve this will be summarized below.

ITARDA INFORMATION■ For preventative safety systems:
It is expected that lane-deviation prevention systems will be expanded to all vehicle models, including
kei-passenger cars, and also improved upon. One point that should be improved upon for the future is
to expand their operating speed range to cover slower speeds.

4 Conclusion

イタルダ インフォメーション

02007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Trends in the number of fatal accidents causedby later-stage elderly people (primary party)
by type of four-wheel vehicle (line graph)and trends in the number of kei-passenger cars owned (bar graph)

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l
SpeciafeatureFatal accidents caused by later-stage elderly people driving kei-passenger cars
~ Be careful of lane departures on main roadways! ~ITARDA INFORMATION no.126

Analysis of characteristic fatal accidents by later-stage

2 elderly people driving kei-passenger cars

The figure on the cover shows the trends in the number of fatal accidents in which a later-stage elderly driver age
75 or older was the primary party (the party who is most at fault of the parties involved in an accident) by type offour-wheel vehicle. This graph indicates that the number of fatal accidents caused by kei-passenger cars
(small-sized passenger cars in Japan) has been rising year by year, increasing to roughly 2.3-fold the number from2007 by 2016.
Why has the number of fatal accidents by later-stage elderly people driving kei-passenger cars increased?
Presumably, this is backed by an increase in the number of later-stage elderly people who own kei-passenger cars.
Fig. 1 shows trends in the number of four-wheel vehicles owned1) and Fig. 2 shows changes in the composition rateof each age group of kei-passenger car owners in 2007 and 2015.2) These graphs indicate that the number ofkei-passenger cars owned is increasing year by year, and that the rate of elderly owners of said vehicles has also
risen. For the future, this is expected to increase at a pace that outstrips that seen so far due to the aging of theso-called baby boomer generation.
Given this backdrop, this issue of ITARDA Information will focus on later-stage elderly driving kei-passenger cars inorder to discuss effective countermeasures for reducing the number of fatal accidents.

Fig. 3 shows the composition rate of fatal accidents by type of accident and primary party. Based on this graph, theclaim can be made that later-stage elderly drivers have a higher share of head-on collisions and collisions withroadside structures compared with all ages, which holds true for both kei-passenger cars and medium-sized
passenger cars. The reason for this is presumed to be because the low impact tolerance of later-stage elderly people
tends to result in fatal accidents when accident do occur, with this tendency particularly pronounced with accidents
involving significant damage to the driver. Although there is some degree of variance in the composition rate due tothe usage conditions when comparing kei-passenger cars and medium-sized passenger cars, the later-stage elderly
driving kei-passenger cars have a somewhat higher rate of head-on collisions compared with the other groups.
Collisions with roadside structures account for the greatest number of fatal accidents among later-stage elderly
people driving four-wheel vehicles, but this issue will perform a detailed analysis on head-on collisions.

Number of four-wheel vehicles owned(10,000 vehicles)

1 Introduction

5,000

Medium-sized passenger cars

75 or older

22

n=924

All ages
n=8,206

Medium- 75 or older
n=1,094
sized
passenger
All agescars
n=14,807

4,000

3,000

Keipassenger
cars

15

13

12

15

14

14

11

12

26

8

4

40

26
16

15

20％
Head-oncollisions

2,000

11

15

0％

Kei-passenger cars

13

19

8

24

4

42

40％

60％

80％

Other

Collisions withroadside structures

Other

Angle
collisions

Vehicle-vehicle accidents

100％
Pedestrianvehicle

Single vehicle(Primary party, total from 2007 - 2016, excluding train accidents)

1,000

Fig. 3. Composition rate of fatal accidents by type of accident

Kei-trucks

0

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

Fig. 1. Trends in the number of four-wheel vehicles owned

0％

20％

40％

60％

80％

100％

To start with, an analysis will be performed on recent changes in the collision safety of kei-passenger cars. Fig. 4
shows the fatality rate (number of fatalities ÷ number of casualties × 100) among drivers from head-on collisions bymodel year of the kei-passenger car involved, which reveals that the newer the model year the lower the fatality
rate. A number of improvements have been made to the collision safety of kei-passenger cars, such as enhancing
their collision safety standards via regulatory revisions in1998 and crafting the legislation for offset frontal collisions.
Therefore, the claim could be made that these are having an effect. However, there is an extremely high fatality
rate among later-stage elderly compared with that for all ages, which hints at the fact that it is no easy feat toprotect later-stage elderly people once a head-on collision accident has occurred. While further improvements are
expected when it comes to collision safety, in addition to this, enhancing “preventative safety” to prevent collisionsin advance will grow more and more important in the future.

FY2007FY2015

17

10

20

21

20

19

22

14

18

20

7

12

Fatality rate (%)

14

All ages

12

75 or older

10
8
6
4
2
0

1998 and earlier

1999 - 20082009 - 2016

Vehicle model year (year) (Primary + secondary parties, wearing seatbelt, total from 2007 - 2016)
Fatality rate (%) = Number of fatalities ÷ number of casualties × 100

20s and under

30s

40s

50s

60s

70s and overFig. 2. Changes in the composition rate by age group of the owners of kei-passenger cars
ITARDA INFORMATION no.126

Fig. 4. Fatality rate of kei-passenger car drivers by vehicle model year (head-on collisions)
In the following section, analyses will be performed on when, where, and why later-stage elderly driving
kei-passenger cars caused fatal head-on collision accidents compared with other drivers in the interest of
preventative safety.
ITARDA INFORMATION no.126

lSpeciafeatureFatal accidents caused by later-stage elderly people driving kei-passenger cars
~ Be careful of lane departures on main roadways! ~ITARDA INFORMATION no.126

Analysis of characteristic fatal accidents by later-stage

2 elderly people driving kei-passenger cars

The figure on the cover shows the trends in the number of fatal accidents in which a later-stage elderly driver age
75 or older was the primary party (the party who is most at fault of the parties involved in an accident) by type offour-wheel vehicle. This graph indicates that the number of fatal accidents caused by kei-passenger cars
(small-sized passenger cars in Japan) has been rising year by year, increasing to roughly 2.3-fold the number from2007 by 2016.
Why has the number of fatal accidents by later-stage elderly people driving kei-passenger cars increased?
Presumably, this is backed by an increase in the number of later-stage elderly people who own kei-passenger cars.
Fig. 1 shows trends in the number of four-wheel vehicles owned1) and Fig. 2 shows changes in the composition rateof each age group of kei-passenger car owners in 2007 and 2015.2) These graphs indicate that the number ofkei-passenger cars owned is increasing year by year, and that the rate of elderly owners of said vehicles has also
risen. For the future, this is expected to increase at a pace that outstrips that seen so far due to the aging of theso-called baby boomer generation.
Given this backdrop, this issue of ITARDA Information will focus on later-stage elderly driving kei-passenger cars inorder to discuss effective countermeasures for reducing the number of fatal accidents.

Fig. 3 shows the composition rate of fatal accidents by type of accident and primary party. Based on this graph, theclaim can be made that later-stage elderly drivers have a higher share of head-on collisions and collisions withroadside structures compared with all ages, which holds true for both kei-passenger cars and medium-sized
passenger cars. The reason for this is presumed to be because the low impact tolerance of later-stage elderly people
tends to result in fatal accidents when accident do occur, with this tendency particularly pronounced with accidents
involving significant damage to the driver. Although there is some degree of variance in the composition rate due tothe usage conditions when comparing kei-passenger cars and medium-sized passenger cars, the later-stage elderly
driving kei-passenger cars have a somewhat higher rate of head-on collisions compared with the other groups.
Collisions with roadside structures account for the greatest number of fatal accidents among later-stage elderly
people driving four-wheel vehicles, but this issue will perform a detailed analysis on head-on collisions.

Number of four-wheel vehicles owned(10,000 vehicles)

1 Introduction

5,000

Medium-sized passenger cars

75 or older

22

n=924

All ages
n=8,206

Medium- 75 or older
n=1,094
sized
passenger
All agescars
n=14,807

4,000

3,000

Keipassenger
cars

15

13

12

15

14

14

11

12

26

8

4

40

26
16

15

20％
Head-oncollisions

2,000

11

15

0％

Kei-passenger cars

13

19

8

24

4

42

40％

60％

80％

Other

Collisions withroadside structures

Other

Angle
collisions

Vehicle-vehicle accidents

100％
Pedestrianvehicle

Single vehicle(Primary party, total from 2007 - 2016, excluding train accidents)

1,000

Fig. 3. Composition rate of fatal accidents by type of accident

Kei-trucks

0

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

Fig. 1. Trends in the number of four-wheel vehicles owned

0％

20％

40％

60％

80％

100％

To start with, an analysis will be performed on recent changes in the collision safety of kei-passenger cars. Fig. 4
shows the fatality rate (number of fatalities ÷ number of casualties × 100) among drivers from head-on collisions bymodel year of the kei-passenger car involved, which reveals that the newer the model year the lower the fatality
rate. A number of improvements have been made to the collision safety of kei-passenger cars, such as enhancing
their collision safety standards via regulatory revisions in1998 and crafting the legislation for offset frontal collisions.
Therefore, the claim could be made that these are having an effect. However, there is an extremely high fatality
rate among later-stage elderly compared with that for all ages, which hints at the fact that it is no easy feat toprotect later-stage elderly people once a head-on collision accident has occurred. While further improvements are
expected when it comes to collision safety, in addition to this, enhancing “preventative safety” to prevent collisionsin advance will grow more and more important in the future.

FY2007FY2015

17

10

20

21

20

19

22

14

18

20

7

12

Fatality rate (%)

14

All ages

12

75 or older

10
8
6
4
2
0

1998 and earlier

1999 - 20082009 - 2016

Vehicle model year (year) (Primary + secondary parties, wearing seatbelt, total from 2007 - 2016)
Fatality rate (%) = Number of fatalities ÷ number of casualties × 100

20s and under

30s

40s

50s

60s

70s and overFig. 2. Changes in the composition rate by age group of the owners of kei-passenger cars
ITARDA INFORMATION no.126

Fig. 4. Fatality rate of kei-passenger car drivers by vehicle model year (head-on collisions)
In the following section, analyses will be performed on when, where, and why later-stage elderly driving
kei-passenger cars caused fatal head-on collision accidents compared with other drivers in the interest of
preventative safety.
ITARDA INFORMATION no.126

Fatal accidents caused by later-stage elderly people driving kei-passenger cars
~ Be careful of lane departures on main roadways! ~ITARDA INFORMATION no.126■ Time periods that fatal head-on collision accidents tend to occur
Fig. 5 shows the composition rate of fatal head-on collision accidents by time period. Fatal accidents caused bylater-stage elderly people occurred more frequently in the daytime relative to all ages. It is conjectured that thereason for this is because later-stage elderly people have few opportunities to go out by car in the early morningand at night for purposes of commuting or the like.
This tendency is not just seen with head-on collisions, but across-the-board with all accidents by later-stage elderly
people.
25

All ages, medium-sized
passenger cars
n=1,456
75 or older, medium-sized
passenger carsn=159
All ages,
kei-passenger cars
n=1,174
75 or older,kei-passenger cars
n=203

15
10

75％
n 203

4-6

6-8

(Secondary party: Four-wheel vehicle, total from 2007 - 2016)

Fig. 5. Composition rate of fatal accidents by time period (head-on collisions)■ Locations where fatal head-on collision accidents tend to occur
Next, the types of locations where fatal head-on collision accidents occurred will be analyzed. Fig. 6 shows thecomposition rate of fatal head-on collision accidents by topography. This graph reveals that approximately 80%
occurred in non-urban areas where there are few homes and structures, with this holding true for all driver types.
Fig. 7 shows the composition rate of fatal head-on collision accidents based on the collision site (primary party: 75
or older driving a kei-passenger car). The term “oncoming traffic lane” within the figure indicates a collision that
occurred up ahead when a vehicle crossed over the center line or center divider or the like, so it can be assumed
that 75% of these were accidents that occurred when the primary party departed from their lane over the center
line. Moreover, Fig. 8 shows the composition rate for different road configurations of the oncoming traffic lane. It
reveals that fatal head-on collision accidents are somewhat more prone to occur along curved road sections rather
than straight ones.
While it is not indicated here, the same sorts of trends were observed among the other driver types.

8
15

80

6
15

6
16

5
16

Urban areas Concentrated
population
Urban areas- Other60

Non-urban areas

77

40

79

77

78

50

75 or older

All agesn 159

n 1,174

Medium-sized passenger cars

40
National highway
Principal local roadPrefectural road
Municipal roadRoutesExpressway
Other

30
20
10
0

m

th

an

5.5

5.5

m

-9

m

9

3
-1

er

m

13

w
or

n

tio

id

I

e
nt

c
rse

n 203
※Figures of less than 10% were omitted

75 or oldern 203

Kei-passenger cars

(Secondary party: Four-wheel vehicle, total from 2007 - 2016)

Fig. 6. Composition rate of fatal accidents by topography (head-on collisions)
ITARDA INFORMATION no.126

Example of a head-on
collision along a curve

16％

ss

n 1,456

n 153

43％

Le
All ages54

Next, Fig. 9 shows the composition rate of fatal head-on collision accidents (primary party: 75 or older driving a
kei-passenger car) by road width and route type. It indicates that such accidents are concentrated on non-intersection
roads between 5.5m and 9m, as well as main roadways such as national highways and principal local roads (butexcluding expressways). Moreover, based on the road width / size, it is conjectured that the majority of these
accidents occurred along general roadways with a single-lane in one direction that are between 5.5m and 9m.
What is not shown here, however, is that since similar tendencies are seen with other drivers this is considered to
be a characteristic of head-on collision accidents in general.

200CurvedFig. 8. Composition rate offatal accidents
by road configurationof oncoming traffic lane(head-on collisions)8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24

Times when accidents occur (hour unit)

100

50％

Other

Fig. 7. Composition rate offatal accidents by collision site(head-on collisions)2-4

46(Primary party: 75 or older driving a kei-passenger car,Secondary party: Four-wheel vehicle, total from 2007 - 2016)

50-2

Straight

0％
Oncoming traﬃc lane

0Composition rate (%)

25％

Composition rate (%)

Composition rate (%)

20

100％

Composition rate (%)

lSpeciafeatureNon-intersections

Road width(Primary party: 75 or older driving a kei-passenger car,Secondary party: Four-wheel vehicle, total from 2007 - 2016)

Fig. 9. Composition rate of fatal accidents by road width and route type (head-on collisions)
ITARDA INFORMATION no.126

Fatal accidents caused by later-stage elderly people driving kei-passenger cars
~ Be careful of lane departures on main roadways! ~ITARDA INFORMATION no.126■ Time periods that fatal head-on collision accidents tend to occur
Fig. 5 shows the composition rate of fatal head-on collision accidents by time period. Fatal accidents caused bylater-stage elderly people occurred more frequently in the daytime relative to all ages. It is conjectured that thereason for this is because later-stage elderly people have few opportunities to go out by car in the early morningand at night for purposes of commuting or the like.
This tendency is not just seen with head-on collisions, but across-the-board with all accidents by later-stage elderly
people.
25

All ages, medium-sized
passenger cars
n=1,456
75 or older, medium-sized
passenger carsn=159
All ages,
kei-passenger cars
n=1,174
75 or older,kei-passenger cars
n=203

15
10

75％
n 203

4-6

6-8

(Secondary party: Four-wheel vehicle, total from 2007 - 2016)

Fig. 5. Composition rate of fatal accidents by time period (head-on collisions)■ Locations where fatal head-on collision accidents tend to occur
Next, the types of locations where fatal head-on collision accidents occurred will be analyzed. Fig. 6 shows thecomposition rate of fatal head-on collision accidents by topography. This graph reveals that approximately 80%
occurred in non-urban areas where there are few homes and structures, with this holding true for all driver types.
Fig. 7 shows the composition rate of fatal head-on collision accidents based on the collision site (primary party: 75
or older driving a kei-passenger car). The term “oncoming traffic lane” within the figure indicates a collision that
occurred up ahead when a vehicle crossed over the center line or center divider or the like, so it can be assumed
that 75% of these were accidents that occurred when the primary party departed from their lane over the center
line. Moreover, Fig. 8 shows the composition rate for different road configurations of the oncoming traffic lane. It
reveals that fatal head-on collision accidents are somewhat more prone to occur along curved road sections rather
than straight ones.
While it is not indicated here, the same sorts of trends were observed among the other driver types.

8
15

80

6
15

6
16

5
16

Urban areas Concentrated
population
Urban areas- Other60

Non-urban areas

77

40

79

77

78

50

75 or older

All agesn 159

n 1,174

Medium-sized passenger cars

40
National highway
Principal local roadPrefectural road
Municipal roadRoutesExpressway
Other

30
20
10
0

m

th

an

5.5

5.5

m

-9

m

9

3
-1

er

m

13

w
or

n

tio

id

I

e
nt

c
rse

n 203
※Figures of less than 10% were omitted

75 or oldern 203

Kei-passenger cars

(Secondary party: Four-wheel vehicle, total from 2007 - 2016)

Fig. 6. Composition rate of fatal accidents by topography (head-on collisions)
ITARDA INFORMATION no.126

Example of a head-on
collision along a curve

16％

ss

n 1,456

n 153

43％

Le
All ages54

Next, Fig. 9 shows the composition rate of fatal head-on collision accidents (primary party: 75 or older driving a
kei-passenger car) by road width and route type. It indicates that such accidents are concentrated on non-intersection
roads between 5.5m and 9m, as well as main roadways such as national highways and principal local roads (butexcluding expressways). Moreover, based on the road width / size, it is conjectured that the majority of these
accidents occurred along general roadways with a single-lane in one direction that are between 5.5m and 9m.
What is not shown here, however, is that since similar tendencies are seen with other drivers this is considered to
be a characteristic of head-on collision accidents in general.

200CurvedFig. 8. Composition rate offatal accidents
by road configurationof oncoming traffic lane(head-on collisions)8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24

Times when accidents occur (hour unit)

100

50％

Other

Fig. 7. Composition rate offatal accidents by collision site(head-on collisions)2-4

46(Primary party: 75 or older driving a kei-passenger car,Secondary party: Four-wheel vehicle, total from 2007 - 2016)

50-2

Straight

0％
Oncoming traﬃc lane

0Composition rate (%)

25％

Composition rate (%)

Composition rate (%)

20

100％

Composition rate (%)

lSpeciafeatureNon-intersections

Road width(Primary party: 75 or older driving a kei-passenger car,Secondary party: Four-wheel vehicle, total from 2007 - 2016)

Fig. 9. Composition rate of fatal accidents by road width and route type (head-on collisions)
ITARDA INFORMATION no.126

lSpeciafeatureFatal accidents caused by later-stage elderly people driving kei-passenger cars
~ Be careful of lane departures on main roadways! ~ITARDA INFORMATION no.126■ Human factors for fatal head-on collision accidents
Next, the question of why fatal head-on collision accidents occurred will be analyzed from the perspective of thehuman factors behind them. Fig. 10 shows the composition rate of fatal head-on collision accidents by human factor.
According to the graph, later-stage elderly drivers tend to engage in a higher share of aimless driving, such as being
lost in thought, relative to all ages, with this rate somewhat on the higher side among later-stage elderly people
driving kei-passenger cars in particular compared with all ages. The reason for this is believed to be because
later-stage elderly driving kei-passenger cars have frequent occasion to drive down roads they are used to travelingdown for short periods of time, so while they do not reach the point of dozing off they do tend to engage in
absentminded driving. In addition, failure to pay attention forward (which includes distracted driving, dozing off whiledriving, being lost in thought, etc.) accounts for roughly half of the accidents among all driver types, which hints at thepossibility that numerous accidents could be prevented in advance if only drivers soundly paid attention to what wasup ahead. Conversely, no significant differences were observed with steering error or judgment error by driver type.

Composition rate (%)

100

12

13

12

10

Other

80

22

20

21

21

Steering error

60

15

17

12

15

Judgment error

40

14

9
11

14
12

13
6

31

29

34

Distracted
driving
Dozing oﬀ
while driving
Lost in thought,
etc.

75 or older

All ages

75 or older

20
0

15

22
All agesn 1,316n 136

Medium-sized passenger cars

n 1,004■ Examples of vehicle-based preventative measures for head-on collisions
Next, vehicle-based preventative measures for head-on collision accidents will be shown. Fig. 13 shows an image ofa lane-deviation warning system. These are systems that mainly use cameras mounted on the vehicle to detect lanes
and issue a warning when it looks like the vehicle is about to deviate from its lane. In 2015 such systems were
equipped on approximately 18% of new vehicles, 4) and they are gradually becoming more widespread. In recent
years, systems that not only provide audible warnings but also cause the steering wheel to vibrate at the same time toencourage caution among drivers have begun to be practically implemented. Meanwhile, Fig. 14 is an image of alane-deviation control system. The major difference between these and the warning systems is that these systems
will intervene in the steering and braking in order to assist the driver in returning to their original lane. The expectationis that these sorts of systems will be effective at combatting accidents caused by operating errors. These systems arestill only equipped on a small number of vehicle models as of now. But in recent years systems that come equippedon compact cars and kei-motor vehicles have begun to appear, and will ideally become even more widespread.
Yet there are cases where both of these systems fail to function as expected on account of the conditions, so
caution is required. For example, it is known that in cases like when the weather is bad or when the center line isblurry it can make it difficult for the camera to detect this. Moreover, it is envisioned that these sorts of systems willordinarily operate when traveling at high speeds, and so at times they fail to operate during low-speed travel.
Drivers must properly understand the limitations of these sorts of systems and make every effort to drive safely
without being over-reliant on them.

Failure to
pay attention
forwardn 169

Fig. 13. Image of a lane-deviation
warning system

Kei-passenger cars

(Secondary party: Four-wheel vehicle, total from 2007 - 2016, excluding cases that could not be investigated)

Considering examples of preventative

3 measures for head-on collisions■ Examples of infrastructure-based preventative measures for head-on collisions
Based on the analytical results thus far, the effectiveness of a number of preventative measures for head-on
collision accidents will be considered. To start with, Fig. 11 shows a high visibility road marking that serves as an
example of an infrastructure-based countermeasure. Since these road markings contain intermittent protrusions
designed to improve visibility, they are effective at preventing drivers from deviating from their lane due to failure to
pay attention forward by producing a noise or vibration when tires pass over them. On the other hand, Fig. 12shows a center line that is called a rumble strip.3) The aim with these is to effectively prevent drivers from deviatingfrom their lane in a similar manner through the installation of indents in the road rather than protrusions. Having
protrusions like those in Fig. 11 presents an obstacle for snow removal, and so these have primarily been adopted
mainly in regions that experience snowfall. Soundly installing and managing these sorts of center lines will serveas an important countermeasure against accidents, particularly for major roadways with a single-lane in one
direction in non-urban areas where head-on collisions frequently occur.

Fig. 14. Image of a lane-deviation
control system■ Improvements for lane-deviation prevention devices
Improvements for these lane-deviation prevention devices will be indicated based on the precautions raised above.
Fig. 15 shows the composition rate of fatal accidents by the danger perception speed of the primary party. For thesake of comparison, data on kei-passenger car drivers age 75 or older and aggregate data on kei-passenger car
and medium-sized passenger car drivers of all ages is shown. This graph reveals that most fatal head-on collision
accidents occurred at speeds of less than 60km/h among all driver types. For later-stage elderly people driving
kei-passenger cars in particular, most accidents occurred within the speed range of 30 - 50km/h, accounting for
68% of the total. For this reason, expanding the operating speed range of lane-deviation prevention systems toencompass lower speeds could potentially prevent an even greater number of fatal accidents in advance.
50

Composition rate (%)

Fig. 10. Composition rate of fatal accidents by human factors (head-on collisions)

Steering
assistanceWarning

40
30

All ages, medium + kei-passenger cars
n=2,493
75 or older, kei-passenger cars
n=191

20

25

10

34

43
27

11

18

0
- 10km/h- 20km/h- 30km/h- 40km/h- 50km/h- 60km/h259Over 60km/h

Danger perception speed of primary party※Figures of less than 10% were omitted(Secondary party: Four-wheel vehicle, total from 2007 ‒ 2016, excluding cases that could not be investigated)

Fig. 11. A high visibility road marking

Fig. 12. A rumble strip※Quoted from the homepage of the Civil Engineering Research Institute for Cold Region

ITARDA INFORMATION no.126

Fig. 15. Composition rate of fatal accidents by danger perception speedof the primary party (head-on collisions)
ITARDA INFORMATION no.126

lSpeciafeatureFatal accidents caused by later-stage elderly people driving kei-passenger cars
~ Be careful of lane departures on main roadways! ~ITARDA INFORMATION no.126■ Human factors for fatal head-on collision accidents
Next, the question of why fatal head-on collision accidents occurred will be analyzed from the perspective of thehuman factors behind them. Fig. 10 shows the composition rate of fatal head-on collision accidents by human factor.
According to the graph, later-stage elderly drivers tend to engage in a higher share of aimless driving, such as being
lost in thought, relative to all ages, with this rate somewhat on the higher side among later-stage elderly people
driving kei-passenger cars in particular compared with all ages. The reason for this is believed to be because
later-stage elderly driving kei-passenger cars have frequent occasion to drive down roads they are used to travelingdown for short periods of time, so while they do not reach the point of dozing off they do tend to engage in
absentminded driving. In addition, failure to pay attention forward (which includes distracted driving, dozing off whiledriving, being lost in thought, etc.) accounts for roughly half of the accidents among all driver types, which hints at thepossibility that numerous accidents could be prevented in advance if only drivers soundly paid attention to what wasup ahead. Conversely, no significant differences were observed with steering error or judgment error by driver type.

Composition rate (%)

100

12

13

12

10

Other

80

22

20

21

21

Steering error

60

15

17

12

15

Judgment error

40

14

9
11

14
12

13
6

31

29

34

Distracted
driving
Dozing oﬀ
while driving
Lost in thought,
etc.

75 or older

All ages

75 or older

20
0

15

22
All agesn 1,316n 136

Medium-sized passenger cars

n 1,004■ Examples of vehicle-based preventative measures for head-on collisions
Next, vehicle-based preventative measures for head-on collision accidents will be shown. Fig. 13 shows an image ofa lane-deviation warning system. These are systems that mainly use cameras mounted on the vehicle to detect lanes
and issue a warning when it looks like the vehicle is about to deviate from its lane. In 2015 such systems were
equipped on approximately 18% of new vehicles, 4) and they are gradually becoming more widespread. In recent
years, systems that not only provide audible warnings but also cause the steering wheel to vibrate at the same time toencourage caution among drivers have begun to be practically implemented. Meanwhile, Fig. 14 is an image of alane-deviation control system. The major difference between these and the warning systems is that these systems
will intervene in the steering and braking in order to assist the driver in returning to their original lane. The expectationis that these sorts of systems will be effective at combatting accidents caused by operating errors. These systems arestill only equipped on a small number of vehicle models as of now. But in recent years systems that come equippedon compact cars and kei-motor vehicles have begun to appear, and will ideally become even more widespread.
Yet there are cases where both of these systems fail to function as expected on account of the conditions, so
caution is required. For example, it is known that in cases like when the weather is bad or when the center line isblurry it can make it difficult for the camera to detect this. Moreover, it is envisioned that these sorts of systems willordinarily operate when traveling at high speeds, and so at times they fail to operate during low-speed travel.
Drivers must properly understand the limitations of these sorts of systems and make every effort to drive safely
without being over-reliant on them.

Failure to
pay attention
forwardn 169

Fig. 13. Image of a lane-deviation
warning system

Kei-passenger cars

(Secondary party: Four-wheel vehicle, total from 2007 - 2016, excluding cases that could not be investigated)

Considering examples of preventative

3 measures for head-on collisions■ Examples of infrastructure-based preventative measures for head-on collisions
Based on the analytical results thus far, the effectiveness of a number of preventative measures for head-on
collision accidents will be considered. To start with, Fig. 11 shows a high visibility road marking that serves as an
example of an infrastructure-based countermeasure. Since these road markings contain intermittent protrusions
designed to improve visibility, they are effective at preventing drivers from deviating from their lane due to failure to
pay attention forward by producing a noise or vibration when tires pass over them. On the other hand, Fig. 12shows a center line that is called a rumble strip.3) The aim with these is to effectively prevent drivers from deviatingfrom their lane in a similar manner through the installation of indents in the road rather than protrusions. Having
protrusions like those in Fig. 11 presents an obstacle for snow removal, and so these have primarily been adopted
mainly in regions that experience snowfall. Soundly installing and managing these sorts of center lines will serveas an important countermeasure against accidents, particularly for major roadways with a single-lane in one
direction in non-urban areas where head-on collisions frequently occur.

Fig. 14. Image of a lane-deviation
control system■ Improvements for lane-deviation prevention devices
Improvements for these lane-deviation prevention devices will be indicated based on the precautions raised above.
Fig. 15 shows the composition rate of fatal accidents by the danger perception speed of the primary party. For thesake of comparison, data on kei-passenger car drivers age 75 or older and aggregate data on kei-passenger car
and medium-sized passenger car drivers of all ages is shown. This graph reveals that most fatal head-on collision
accidents occurred at speeds of less than 60km/h among all driver types. For later-stage elderly people driving
kei-passenger cars in particular, most accidents occurred within the speed range of 30 - 50km/h, accounting for
68% of the total. For this reason, expanding the operating speed range of lane-deviation prevention systems toencompass lower speeds could potentially prevent an even greater number of fatal accidents in advance.
50

Composition rate (%)

Fig. 10. Composition rate of fatal accidents by human factors (head-on collisions)

Steering
assistanceWarning

40
30

All ages, medium + kei-passenger cars
n=2,493
75 or older, kei-passenger cars
n=191

20

25

10

34

43
27

11

18

0
- 10km/h- 20km/h- 30km/h- 40km/h- 50km/h- 60km/h259Over 60km/h

Danger perception speed of primary party※Figures of less than 10% were omitted(Secondary party: Four-wheel vehicle, total from 2007 ‒ 2016, excluding cases that could not be investigated)

Fig. 11. A high visibility road marking

Fig. 12. A rumble strip※Quoted from the homepage of the Civil Engineering Research Institute for Cold Region

ITARDA INFORMATION no.126

Fig. 15. Composition rate of fatal accidents by danger perception speedof the primary party (head-on collisions)
ITARDA INFORMATION no.126

No.126■ For road environments:
The expectation is that thorough maintenance and management will be carried out for center lines
and road shoulders of major roadways, since uneven surface conditions prevent drivers fromdeviating from their lanes and will boost detection by vehicles with onboard cameras.

渉外事業課

TEL 03-5577-3973

FAX 03-5577-3980

公益財団法人 交通事故総合分析センター●ウェブサイト http://www.itarda.or.jp/ ●Eメール koho@itarda.or.jp●フェイスブック https://www.facebook.com/itarda.or
本部〒101-0064 東京都千代田区神田猿楽町2-7-8 住友水道橋ビル8階
TEL 03-5577-3977(代表) FAX 03-5577-3980

ITARDA INFORMATION no.126

つくば 交通事故調査事務所

住 友 水 道 橋 ビル８ 階

イタルダインフォメーションに関するお問い合せ先

交通事故分析レポート No.126

200

About 2.3-fold
Medium-sized
passenger cars

4since 2007

150

3
Kei-trucks

1002

Kei-passenger cars
50

1

0

Number of kei-passenger cars owned(10 million vehicles)

参 考文 献1) 日本自動車工業会：自動車保有台 数 統 計 資 料2) 日本自動車工業会：「2015年度 軽自動車の 使 用実態 調 査 報 告書」, 2016年 3月
3) 寒 地土木研究 所 平澤 他：「新しい事故 対 策手法としてのランブルストリップスの開発と実 用化に関する研究」，
土木学 会論文集 第４部門 NO.800 / Ⅳ−69，2005年10月．
4) 国土 交 通省：ASV技術普及状 況 調 査 資 料
5) ITARDA 三枝：「軽 乗 用車運 転中の 後 期高齢 者による死亡事故の 特 徴と対 策」,設 立25周年記 念フォーラム論文, 2017年10月

3〒101 0064 東 京 都 千 代 田 区 神 田 猿 楽 町 ２ ７ ８(Tatsuhiko Saegusa)

30

公益財団法人 交通事故総合分析センター■ In conclusion
Kei-passenger cars play an indispensable role as an important means of transportation that offers analternative to local public transportation for elderly people. In aiming to further reduce the number offatal accidents among such drivers, it is not enough to just rely on improvements to the collision safetyof vehicles. Rather, initiatives to popularize and advance preventative safety technology (includingthat for infrastructure), as well as those for integrated safety on the part of society as a whole(including post-accident care) are growing increasingly important. The expectation is that safety will
be further enhanced by actually promoting such initiatives.

ITARDA INFORMATION

Number of fatal accidents (accidents)

交通事故分析レポート■ For driving awareness by elderly drivers:
Aimless driving results in the occurrence of a great many head-on collision accidents. Elderly drivers
are encouraged to reaffirm the risk of head-on collisions on roads with oncoming traffic, and shouldmake efforts to drive by focusing their attention even when driving on familiar roads during thedaytime.

This analysis revealed that countermeasures against head-on collision accidents involving
kei-passenger cars, especially preventing deviations from one’s lane, are important for the sake of
reducing the number of fatal accidents caused by later-stage elderly drivers. As such, expectations
regarding ways to achieve this will be summarized below.

ITARDA INFORMATION■ For preventative safety systems:
It is expected that lane-deviation prevention systems will be expanded to all vehicle models, including
kei-passenger cars, and also improved upon. One point that should be improved upon for the future is
to expand their operating speed range to cover slower speeds.

4 Conclusion

イタルダ インフォメーション

02007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Trends in the number of fatal accidents causedby later-stage elderly people (primary party)
by type of four-wheel vehicle (line graph)and trends in the number of kei-passenger cars owned (bar graph)

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