ITARDA 20th WorkShop Report

Characteristics of and causative factors for accidents by elderly drivers
Hiromu Shibasaki, Senior Researcher

Overview
The number of traffic accident fatalities in 2016 came to 3,904 people, a decline of 213 from the previous
year. Elderly people accounted for 54.8% of these, with their rate increasing year by year. In addition, as aresult of the increase in the number of elderly people with driver’s licenses, there has been a 1.8-foldupswing in the rate of fatal accidents caused by elderly people driving medium-sized and small-sized motor
vehicles over the past ten years, with this having come to pose a social problem. The major causative factor
for the accidents that can be mentioned is the decline in physical function that accompanies aging, but what
is happening to elderly drivers who have driven safely over a long time? This study seeks to bring to lightthe characteristics of accidents due to human errors unique to elderly drivers and the true causes for thembased on accident data from within Japan. It will also discuss measures to reduce the number of accidents
in the future.

1.

Introduction

Even as the number of fatalities from traffic accidents in 2016 declined by 213 people from the previous
year down to 3,904, the percentage of fatalities among elderly people age 65 and over has been trending
upward year by year, accounting for as much as 54.8% of these. Moreover, this reveals that their fatality
rate, which indicates the percentage of fatalities versus casualties, has risen to 6.4-times that of non-elderly
people.
This is presumably influenced by the rise in the proportion of the elderly population in Japan. The
government is aiming to achieve the objective of “realizing the safest road transport in the world bydecreasing fatalities within 24 hours to less than 2,500 per year by 2020,” which was set forth in its Tenth
Traffic Safety Basic Plan. It goes without saying that reducing the number of fatal accidents by elderly
people holds the key to achieving this objective.

In recent years, the number of elderly people withdriver’s licenses has soared, which in turn has led to an increase in the number of traffic accidents caused
by elderly drivers. This has come to pose a serious social problem. Therefore, as traffic accidents caused byelderly drivers is one of the mainstays of the research that ITARDA must address, this paper will explore
the question: Why do elderly drivers tend to cause more accidents despite having continued to drive safely
over many years? As such, this paper will consider the characteristics of accidents unique to elderly people
based on an analysis of accidents using macrodata and microdata on traffic accidents based on the humanfactors in play, consider how to reduce accidents, and discuss measures for this.

2.

Background / Goals

Fig. 1 shows the casualty composition rate by status for each age group in 2016 together with the fatality
rate, which indicates the percentage of fatalities versus casualties. While the age group of elderly people

1ITARDA 20th Work Shop Reportage 65 and over is seeing a drop in its casualty composition rate while driving automobiles, conversely its
casualty composition rate while walking or riding a bicycle is trending upwards. It also indicates that they
have a conspicuously high fatality rate as pedestrians in particular. However, the slope of the line graphshowing the changes in the fatality rate for elderly people while driving an automobile reveals that as
people grow older, they exceed the rate of increase in the fatality rate among pedestrians. Based on suchcircumstances, Fig. 2 shows the changes in the number of fatal and casualty accidents over the past ten
years up through 2016, with 2007 taken as the baseline year for accidents in which an elderly driver drivinga passenger car or truck (hereafter referred to as “four-wheel vehicles”) was involved as the primary
party.*1

10%

80%

8%
60%
6%
40%
4%
20%

2%

85～

75～84

65～74

55～64

45～54

35～44

25～34

0%

16～24

0%

Fatality rate = Fatalities/casualties×100

12%

～15

Casualty composition rate (bar graph)

100%

歩行者
Pedestrians

自転車
BicyclesMopeds
原付

Two-wheel
自動二輪
vehicles

Vehicle自動車同乗
occupants

Vehicle自動車運転
drivers

Two-wheel
自動二輪
vehicles

原付
Mopeds

自転車
BicyclesPedestrians
歩行者

Vehicle自動車同乗
occupants

Vehicle自動車運転
drivers("Vehicles" excludes special vehicles, 2016)(Age group)

Fig. 1. Casualty composition rate and fatality rate by status

0.2

Passenger vehicles –medium-sized
motor vehicles
乗用車-普通車

Elderly drivers (65+)

WorseCasualties

Fatalities

Elderly
0.0

Passenger vehicles –乗用車-軽自動車
small-sized
motor vehicles

Trucks – medium-sized
貨物車-普通車
motor
vehiclesTrucks – small-sized motor
貨物車-軽自動車
vehiclesOtherfour-wheel vehicles
その他四輪車Two-wheel
二輪車 vehicles

Casualties
死傷

51

3

26

14 2 4

Change index

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Fatalities
死亡

30

-0.2

4

29

24

4 9

7

28

6 54

24

7 13 13

Non-elderly
Casualties
死傷

50

-0.4
死亡
Fatalities

Non-elderly (16-64)36

6Better

0%

-0.6

50%

100%
(Primary party, 2016)(Primary party: Mopeds and larger (excluding special vehicles, trams, and trains),
age 16 and over)Fig. 2. Trends in accidents by elderly / non-elderly drivers

2

Fig. 3. Rate of accidents by vehicle type

ITARDA 20th Work Shop Report

Looking at the non-elderly group (age 64 or under) reveals that this is heading in a positive direction, given
the downward trajectory this is on year by year. However, casualty accidents by the elderly group areholding steady and fatal accidents have been trending upwards since 2013, with some degree of fluctuation
up and down. Fig. 3 shows the composition rate for the number of accidents by type of party between
four-wheel vehicles and two-wheel vehicles in 2016. This indicates that the increase in fatal accidents byelderly drivers driving small-sized trucks has been striking compared to the rate of casualty accidents byelderly drivers driving small-sized motor vehicles of 40% (26% from small-sized passenger cars + 14%
from small-sized trucks). These accidents account for 53% (29% from small-sized passenger cars + 24%
from small-sized trucks) of the total, and are growing compared with the rate for non-elderly people.
*1

Primary party: This refers to the party at greater fault of the vehicle drivers or pedestrians initially involved ina traffic accident. Or if both parties are at equal fault, then it refers to the party that sufferedless physical harm.

In order to reduce the fatal accidents caused by elderly drivers mentioned above, which are on an upward
trajectory year by year, this paper will focus on “accidents in which an elderly driver was involved as theprimary party.” It will use traffic accident macrodata and micro accident research data to analyze and sortout the actual status for accidents caused by elderly drivers. By doing so, it will clarify the causative factors
for such accidents and obtain source data for reducing fatal accidents in the future.

3.

Actual status and characteristics of accidents by elderly drivers

Fig. 4 shows the trends in the numbers of fatal and casualty accidents up through 2016 by using 2007 as thebaseline year. It narrows down the vehicles subject to analysis to four-wheel vehicles, which frequently get
into accidents, and divides up the elderly driver group into early-stage elderly (ages 65 – 74) and later-stageelderly (ages 75 and over). Whereas the number of accidents by those in the non-elderly group (ages 18 –64) has been decreasing and thus improving year by year, the number of fatal accidents by early-stageelderly has been on an upswing over these four years, despite some fluctuation up and down. Among thelater-stage elderly group, the number of such accidents has continued to rise since 2009, thus continuing toworsen in the form of a 24% increase over the ten-year period. Conversely, while the number of casualty
accidents has been slightly trending downwards since 2014, this decrease has been slowing down. As the
proportion of the population consisting of elderly people continues to increase in the future, it is projectedthat the number of fatal accidents will continue to rise still further unless more effective measures are taken
to counter this.

(1) Current status of accidents involving an elderly driver as the primary party
What types of accidents do elderly drivers frequently cause? Fig. 5 shows the composition rate for thenumber of accidents by accident type involving elderly drivers driving either medium-sized or small-sized
vehicles as the primary party, as well as the occurrence rate of fatal accidents, which shows the percentage
of fatal accidents versus casualty accidents (hereafter referred to as the “fatal accident rate”). The rate of3

ITARDA 20th Work Shop Reportcasualty accidents consisting of single vehicle accidents is low at 3%, versus 84% for vehicle-vehicle
accidents and 13% for pedestrian-vehicle accidents. This reveals that as opposed to rear-end collisions,which are most commonly seen among non-elderly drivers, elderly drivers cause a higher rate of accidents
in settings that require awareness of the traffic environment and judgment of the circumstances, such as
angle collisions or collisions while turning left / right. Conversely, when it comes to the fatal accident rate,
extremely high values are seen with single vehicle accidents like running off the road and collisions withroadside structures, while head-on collisions have extremely high rates among vehicle-vehicle accidents.
The rates for later-stage elderly drivers indicated by the numbers in parentheses are even higher.
Worse

Fatalities(solid line)

Casualties(dotted line)

0.3

75 and over

0.2

Change index

0.1
0.0
2007

-0.1

2008 2009 2010 2011 20122013 20142015 2016ages 65-74

-0.2
-0.3
-0.4

Non-elderly (18-64)-0.5

Better (Primary party: Medium- +small-sized motor vehicles, Non-elderly people:18-64)

Fig. 4 Trends in the number of accidents by age group

Casualty accident

Fatal accident occurrence rate30%

Non-elderly drivers

Elderly drivers

43%

40%

20.9% (24.7)
30%

Vehiclevehicle: 84%

22%

10%

Vehiclevehicle: 90%

Other
その他

Other

その他

Crossing pedestriancrossings
横断歩道横断Outside pedestrian
横断歩道以外crossings
Walking facing /対背面通行中parallel to vehicle

Running路外逸脱
off the road

0%

Other
その他
Collisions with roadsidestructures
工作物衝突

Rear-end collisions
追突
Collisions while turning
left / right
右左折時

Other
その他

Angle
collisions
出会い頭Walking facing /対背面通行中parallel to vehicle

Outside pedestrian

横断歩道以外crossings

Other
その他
Crossing pedestrianSinglePedestrianvehicle: 3% vehicle: 13%

5.5%

2.6%
Head-oncollisions
正面衝突

12%

6.7%

4.1%

横断歩道横断crossings

Running
off the road
路外逸脱

16%
Angle
collisions
出会い頭

0%

5.7% (7.6)
Head-oncollisions
正面衝突

10%

Other
その他
Collisions with roadside
工作物衝突
structures29%

10.2% (12.5)

24%

20%

20%

15.4%

Rear-end collisions
追突
Collisions while turning
右左折時
left / rightCasualty accident composition rate50%

死亡事故発生率(later-stage elderly people)

SinglePedestrianvehicle: 1% vehicle: 9%(Primary party: Medium- +small-sized motor vehicles, 2016)

Fatal accident occurrence rate = Fatal/casualty accidents×100

死傷事故構成率
composition rate

Fig. 5. Casualty accident composition rate and fatal accident rate by type of accident

4

ITARDA 20th Work Shop Report

This reveals that the fatal accident rate for accidents involving elderly people running off the road isparticularly high at 20.9%, and is particularly severe among later-stage elderly at 24.7%. It is believed thatthe majority of these accidents are mainly caused by drivers deviating from their lane while driving as aresult of operating errors, or from braking errors.(1) Therefore, this study will focus on accidents with a highoccurrence rate from among all accident types, including angle collisions, rear-end collisions, andcollisions while turning left / right, as well as head-on collisions, which have a high fatal accident rate, andcollisions with roadside structures and running off the road, which both represent single vehicle accidents.
The characteristics of and causes for these types of accidents will be analyzed below.

(2) Characteristics of accidents by elderly drivers[1] Locations where accidents by elderly drivers frequently occur
Fig. 6 shows the composition rate for the number of casualty and fatal accidents for each type of accident
by primary party and by road configuration over the ten-year period from 2007 to 2016. This is done for theroad environments where angle collisions, collisions while turning left / right, and rear-end collision
accidents occurred, which involve numerous casualty accidents due to collisions with four-wheel vehicle,
as well as head-on collisions, collisions with roadside structures and accidents from running off the road,which have a high fatal accident rate. The analysis was performed by focusing on four-wheel vehicles andtwo-wheel vehicles regarding the secondary party.*2
The rates of angle collisions and collisions while turning left / right, which are accidents that frequently
involve elderly drivers, for those that occurred at intersections are extremely high at 88% and 72%,
respectively. For angle collisions, 76% of these occurred at non-signalized intersections, while 61% of
collisions while turning left / right occurred at signalized intersections. This reveals that elderly drivers
account for a larger rate of both types of accidents at non-signalized intersections over non-elderly drivers.
They also account for no small rate of the accidents along non-intersection roads, such as collisions withother vehicles when pulling out onto a road from a parking lot, gas station, or similar entrance along
roadways at 9% and 21%, respectively. Intersections are locations where a great deal of traffic converges
and intersects. Since no traffic controls are instituted via traffic lights at non-signalized intersections, there
is a particular need for drivers to acknowledge and make decisions on the surrounding traffic environmenton their own, and control their vehicle in accordance with this.

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ITARDA 20th Work Shop Report

Signalizedintersections
信号機有り交差点

Non-signalizedintersections
信号機無し交差点

Near
intersections
交差点付近

Non-intersections(curved roads)
単路/カーブNon-intersections
単路/直線(straight
roads)Store
parking lots, etc.
店舗駐車場等

Angle
collisions

Elderly
高齢者

21

67

9

非高齢者
Non-elderly

21

65

10

44

28

21

43

25

25

Collisions Elderly
高齢者
while
turning
非高齢者
Non-elderlyleft / rightRear-end
collisions

Elderly
高齢者

30

58

Non-elderly
非高齢者

27

61

Frequentlyoccuring
accidents

0% 20% 40% 60% 80% 100%
Occurence rate of casualty accidents(Rates under 10% omitted)

高齢者
Elderly
Head-oncollisions
Non-elderly
非高齢者

高齢者
Collisions Elderly
withroadside Non-elderly
非高齢者
structures
Elderly
高齢者
Running
off theNon-elderly
非高齢者
road

High fatality
rate accidents

46

46

48

43

12 12
10

34
37
43

42

32
41
26

14

42

0% 20% 40% 60% 80% 100%
Occurrence rate of fatal accidents(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger(excluding special vehicles, trams, and trains), 2007-2016)

Fig. 6. Occurrence rates of casualty / fatal accidents by road configuration and by presence or absence of traffic
signal for each accident type

Therefore, compared with signalized intersections there is an extremely large number of factors that must
be confirmed at non-signalized intersections, and they represent an environment that is prone to angle
collision accidents. However, for collisions while turning left / right many of the accidents occurred at
signalized intersections and, as will be discussed later on, it is known that most of these accidents consist ofcollisions with oncoming vehicles moving straight when turning right. As for rear-end collisions, 58% of
these occurred at non-intersections (straight roads), with 30% of these occurring near intersections. The
majority of these are believed to have been caused by a failure to brake in time due to a delay in detecting
the vehicle up ahead owing to careless driving or a failure to pay attention forward, or an extended braking
distance resulting from the driver’s weakened ability to press the brake, regardless of how fast the vehicle
was moving.
Conversely, with accidents involving running off the road, which carry the highest fatal accident rate, therate of accidents at non-intersections (curved roads) is particularly high at 43%. Presumably, the drivers inthese accidents failed to realize there was a curve up ahead due to a failure to pay attention forward orsimilar reason, or realized this right before reaching it but were unable to do anything about it, resulting in
accidents due to improper driving operations. The rate of these accidents that occur at general traffic
locations like store parking lots comes to 14%, with these being characterized by their prevalencecompared with the other accident types. Furthermore, 22% of collisions with structures installed along thesides of roads occurred in the vicinity of these locations (which include intersections), while 78% occurred

6

ITARDA 20th Work Shop Reportat non-intersections. This also reveals that the vast majority of head-on collisions occurred at
non-intersections at 92%. In cases where drivers deviate from their lane for some reason, such as due tooperating errors, at non-intersections (including curved roads) and get into head-on collisions withoncoming vehicles or collide with utility poles or protective fences, the objects they collide with may differ,
but they presumably share the same qualities that lead up to the occurrence of fatal accidents.
*2

Secondary party: This refers to the party at lesser fault of the vehicle drivers or pedestrians initially involved ina traffic accident. Or if both parties are at equal fault, then it refers to the party that suffered
greater physical harm.

[2] Road environments at locations where accidents by elderly drivers frequently occur
As opposed to the road configurations where accidents frequently occur mentioned in the preceding
paragraph, Fig. 7 similarly shows the composition rates for the number of casualty and fatal accidents byroad environment, such as road width, for the type of accidents regarding casualty accidents that occur
frequently and those with high fatal accident rates.
Community
roads (less than 5.5m)
生活道路(5.5m未満)

Generalroads (single lane in one direction)
一般道路(片側1車線)

Major
roads (multiple lanes in
幹線道路(複数車線)
one direction)Storeparking lots, etc.
店舗駐車場等

Angle
Elderly
高齢者
collisions
Non-elderly
非高齢者
Collisions
Elderly
高齢者
while
16
turningleft / right Non-elderly
非高齢者 15
高齢者 12Rear-end Elderly
collisions
非高齢者 12
Non-elderly
0%

43

47

9

42

46

11

50

32

48

36

50

37

47

41

Head-oncollisions

Elderly
高齢者

77

18

Non-elderly
非高齢者

74

22

Collisions 高齢者
Elderly 18
withroadside Non-elderly
非高齢者 10
structures
Elderly
高齢者
Running
off theNon-elderly
road
非高齢者

20% 40% 60% 80% 100%

61

57
49

31

17

32
33
52

14
8 8

0% 20% 40% 60% 80% 100%
Occurrence rate of fatal accidents

Occurrence rate of casualty accidents(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger(excluding special vehicles, trams, and trains), 2007-2016)

Fig. 7. Occurrence rates of casualty and fatal accidents by road type for each accident typeIn general, accidents on general roads with single lane in one direction, which is the most common type ofroad in Japan, account for the majority of these. A higher rate of angle collisions is seen on community
roads where the road is less than 5.5m wide, while a higher rate of collisions while turning left / right andrear-end collisions occur along major roads with multiple lanes in one direction. However, virtually no
difference is seen between elderly people and non-elderly people. Conversely, a large percentage ofaccidents involving running off the road occur on narrow roads like community roads at 49%. These
conceivably lead to serious accidents, including those where the driver’s wheels run off into roadsideditches and their vehicle overturns, as well as where the vehicle falls into a field or waterway that is lower

7

ITARDA 20th Work Shop Reportthan the road, or where they collide with structures off the side of the road. This also reveals that 14% of
fatal accidents occur in store parking lots and the like, which is a relatively large rate compared with othertypes of accidents.

[3] Danger perception speed of elderly drivers
Generally speaking, the faster the traveling speed of the vehicle when collision accidents occur the greater
the force of the collision, while the larger the size and greater the weight of the vehicle collided with thegreater the damage done to one’s vehicle, resulting in more serious accidents. Therefore, Fig. 8 shows thecomposition rate for the number of accidents divided up into 10km increments when the danger perception
speed is 60km/h or less, (2) where most accidents involving elderly drivers occur, and those over 60km/h, by
type of accident using the danger perception speed as one of the indicators. The danger perception speed isthe speed the vehicle was traveling when the elderly driver driving the primary vehicle detected the othervehicle and perceived that they were in danger of colliding with said vehicle. This shows that the types ofaccidents that occur most frequently are angle collisions and collisions while turning left / right, with the
majority of these occurring at low speeds of 30km/h or less at 84% and 95%, respectively. It also reveals
that for rear-end collisions this grows to 36% at moderate to high speeds over 30km/h. However, it also
indicates that there is virtually no difference when you compare the casualty accident composition rate bydanger perception speed of elderly drivers and non-elderly drivers for each type of accident. Conversely,with head-on collisions and collisions with roadside structures, which have a high fatal accident rate, bothof these have a high rate of fatal accidents at moderate to high speeds of over 40km/h at 75% and 53%,
respectively. As opposed to this, accidents from running off the road account for 15% of the accidents that
occur at extremely low speeds of 10km/h or less compared with other accident types. However, this type of
accident occurs at the same rate across all the speed ranges for danger perception speeds of 50km/h or less.
Running off the road can lead to one’s vehicle falling, toppling over, rolling over, or colliding withstructures off the side of the road after one’s vehicle has deviated off, regardless of how fast the vehicle
was traveling. This tends to inflict lethal damage on the vehicle’s passengers, and therefore it could be
described as an extremely serious accident type. In addition, on comparing the composition rates for thedanger perception speeds of elderly drivers and non-elderly drivers, you find that elderly drivers do not go
as fast as non-elderly drivers and drive in a compensatory manner that lessens the risk of accidents to somesmall extent by curbing their speed.(3) Yet despite this, elderly people are connected to fatal accidents forsome reason that is unique to them.

8

ITARDA 20th Work Shop Report

～10

～20

～30

～40

～50

～60

Over
60超60

(km/h)

Elderly
高齢者

40

30

14 12

Non-elderly
非高齢者

39

29

14 11

Angle
collisions

Collisions Elderly
高齢者
while
turning Non-elderly
非高齢者
left / rightRear-end
collisions

45

42

8

45

41

8

Elderly
高齢者

30

17

17

22

10

Non-elderly
非高齢者

29

18

17

20

11

Frequentlyoccurring
accidents

0%

Head-oncollisions

高齢者
Elderly20

非高齢者 10Non-elderly

Collisions Elderly
高齢者
withroadside Non-elderly
非高齢者
structures

42

24

32

28

28

30

28

15 10

12
11 16

15

54

Elderly21
高齢者 15 18 17
Running
off theNon-elderly
非高齢者 6 7 11 14 14 17
road

20% 40% 60% 80% 100%0%High fatality
rate accidents

Occurrence rate of casualty accidents

9

14 8
31

20% 40% 60% 80% 100%

Occurrence rate of fatal accidents(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger(excluding special vehicles, trams, and trains), 2007-2016)

Fig. 8. Occurrence rates of casualty and fatal accidents by danger perception speed for each accident type[4] Characteristics of accidents by elderly drivers at intersections
This section will take a look at the current status of intersection accidents, which frequently consist ofcasualty accidents caused by elderly drivers driving four-wheel vehicles, by whether the intersection was
signalized or non-signalized.
・Status of accidents at signalized intersections
Angle collisions and collisions while turning left / right at signalized intersections are typical collision
accidents that account for 31% of the total number of accidents at intersections. For these, the composition
rate for the number of collision casualty accidents between an elderly driver driving a four-wheel vehicle as
the primary party and a four-wheel vehicle or two-wheel vehicle as the secondary party by type of
movement of the primary party is shown in Fig. 9 in the figure on the left, while a breakdown that also

Secondary party composition rate(%)

includes the direction of movement of the secondary party is shown in the bar graph on the right.
Casualty accident
composition rate
(%)

27
43
24

N=54,893

50

40

8

←Mopeds30

10←Motorized two-wheel
vehicles

20
10
0

25

24

21

Medium- & small-sized
motor vehicles
Moving直進
straight

Primary
party →

Turning
右折
right

Secondary
party →

対向
左→右
右→左
→ leftOncoming
Left→ right Right

Moving直進
straight

Direction of motion(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger (excluding special vehicles,
trams, and trains), intersections, angle collision + collision while turning left / right accidents, 2007-2016)

Fig. 9. Status of accidents involving elderly drivers as the primary party at signalized intersections

9

ITARDA 20th Work Shop Report

As can be gleaned from the rate of accidents, accidents between a vehicle turning right and one moving
straight involving an elderly driver as the primary party colliding with an oncoming vehicle when turning
right are the most typical at 43%, with motorized two-wheel vehicles (including mopeds) accounting for
18% of these. With these, numerous cases of accidents were seen in which the elderly driver completely
failed to notice the other party prior to colliding with them. These were due to reasons such as misjudging
the speed of or sense of distance to the oncoming vehicle as a result of the declining dynamic visual acuitythat comes with aging as one reaches old age, or from failing to perceive the oncoming vehicle within theirvisual field for reasons such as a narrowing of their visual field. Moreover, there are numerous accidents
involving collisions with vehicles coming from the left or right, regardless of whether or not theintersection had a traffic signal. From the analysis it was learned that most of these were caused by the
person failing to notice the traffic signal.
・Status of accidents at non-signalized intersections
Angle collisions and collisions while turning left / right at non-signalized intersections account for 69% of
the total for all accidents at intersections. The status for these collision accidents is shown in Fig. 10,
similar to the accidents at signalized intersections. This reveals that the nature of accidents involving
elderly drivers as the primary party at non-signalized intersections differ slightly from those of accidents at
signalized intersections. Whereas there were a great many accidents between a vehicle turning right andone moving straight at signalized intersections, these were rare at non-signalized intersections at 7%. The
most common accident pattern involved the primary party vehicle driven by an elderly driver entering theintersection with the intention of moving straight and immediately colliding with a vehicle that had been
approaching from the left. Such accidents account for 37% of the total. Moreover, collisions with vehicles
approaching from the right are also common at 29% of the total. There is also no shortage of cases
involving collisions with vehicles approaching from the right immediately after entering an intersection
with the intention of turning right, at 13%. The declining physical function that results from aging isthought to have a considerable impact on accidents that occur when moving straight through an intersection.
Examples of this include overlooking stop signs, noticing that there is a stop sign but being unable to bring
one’s vehicle to a stop in time, or the aforementioned narrowing of one’s visual field or small angle withwhich elderly drivers can turn their heads when checking that it is safe on either side.

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ITARDA 20th Work Shop Report

37

Secondary party composition rate (%)

Casualty accident
composition rate
(%)

6
7

29
6

13

N=123,085

40

30

4
2

←Mopeds←Motorized two-wheel vehicles

4
2
20

31
22

10

0

3
2

2
2
3

Medium- & small-sized
7
motor vehicles
Moving Turning
直進 right
右折
straight

Turning右折
rightPrimary
party →

Moving直進
straight

Secondary
party →→→ Oncoming
Left→ Right
左→右
右→左 Right
右→左
対向
left
left
right

Direction of motion(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger (excluding special
vehicles, trams, and trains), intersections, angle collision + collision while turning left / right accidents, 2007-2016)

Fig. 10. Status of accidents involving elderly drivers as the primary party at non-signalized intersections

4.

Causative factors for accidents by elderly drivers

The previous section discussed the characteristics of accidents commonly caused by elderly drivers and six
accident types with high fatal accident rates. Now, we will look at the question of why these accidents
occurred by focusing on the factors of driver’s legal violations and human negligence from among thecausative factors intertwined with many of these accidents.

(1) Legal violations serving as causative factors for accidents
Many traffic accidents are caused by legal violations. Fig. 11 shows the status for this in terms of thecomposition rate for the number of casualty accidents and number of fatal accidents by major legal
violations for each type of frequently-occurring accident, high-fatality rate accident, and road configuration(including traffic signals). The locations where accidents occurred for each type of accident are indicatedby narrowing this down to respective locations where a large rate of accidents occurred as shown in Fig. 6.
Regarding accidents that frequently occur at intersections, the majority of these were caused by a failure toconfirm safety factors and violations of mandatory safe driving. As for angle collisions at non-signalizedintersections, violations involving a failure to come to a stop accounted for 38% of the total of these.
However, almost no difference was seen in the rates for this based on age. Collisions while turning left /right at these same non-signalized intersections have a lower rate accounted for by a failure to come to astop, but conversely more of them are due to a failure to confirm safety factors and failure to observe
surrounding traffic movement. With these same collisions while turning left / right, a low rate of them arecaused by violations involving ignoring traffic signals at signalized intersections, but this is trending
upwards. The rate of violations involving a failure to come to a stop and ignoring traffic signals tend toincrease among elderly people the older they get, presumably because of their increased number ofperceptual errors such as failing to notice traffic signals, signs, and road markings. (4) Distraction accounts

11

ITARDA 20th Work Shop Reportfor a large number of rear-end collisions at 38%, but this also reveals that they engage in all manner ofother violations aside from this. When you consider the range of danger perception speeds of elderly
drivers for the accidents that occurred in Fig. 8, then presumably the nature of each violation differs. Of
these, operating errors such as delay in applying the brakes were more common with elderly people thanwith non-elderly people. The claim could be made that this is affected in no small part by their decline inphysical function, such as misreading the distance between their vehicle and the preceding vehicle, ordecrease in power to press the brake pedal.

安全不確認
Failure to come to a stop
一時不停止
Ignore signal
信号無視
Absent-minded driving
漫然運転

Failure to observe surrounding traffic
動静不注視
movement
Duty
to pass safely through intersections
交差点安全進行義務

Failure to confirm safety factors

Angle collisions(non-signalizedintersections)

高齢者
Elderly

42

38

16

非高齢者
Non-elderly

44

35

17

62

8

21

Head-on
高齢者
collisions (non- Elderlyintersections)

32

50

16

66

7

20

非高齢者
Non-elderly

37

43

17

Collisions while
Elderly
高齢者turning left / right(non-signalizedintersections)
非高齢者
Non-elderly

高齢者
Collisions while
Elderlyturning left / right(signalized
Non-elderly
非高齢者intersections)
高齢者
Rear-end
Elderly
collisions (nonintersections/Non-elderly
非高齢者
straight roads,
near intersections)0%Frequentlyoccurring accidents

55

10

21

8

57

9

21

9

20

18

18

38

23

12 17

41

Collisions
Elderly
高齢者with roadsidestructures(nonNon-elderly
非高齢者intersections)

Elderly
高齢者

Running off
the road(nonNon-elderly
非高齢者intersections

20% 40% 60% 80% 100%

Occurrence rate of casualty accidents

Operating errors
操作不適
Distracted driving
脇見

8

49

34

15

57

30

12

66

15 12

65

24

8

0% 20% 40% 60% 80% 100%
High fatality rate
accidents

Occurrence rate of fatal accidents(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger (excluding
special vehicles, trams, and trains), 2007-2016)

Fig. 11. Occurrence rates of casualty / fatal accidents by legal violation for each type of accident and roadconfiguration

Fig. 6 indicated that most accidents with a high fatal accident rate occur at non-intersections. But more than
80% of all accident types are caused by operating errors or careless driving. The rate of head-on collisions
and collisions with roadside structures accounted for by careless driving tends to be higher with elderly
people than with the non-elderly. It is believed that such accidents occur for reasons like the driver being
delayed in realizing that their vehicle has strayed from its path of motion as a result of careless driving and,
when something unexpected suddenly happens, getting flustered and suddenly turning the wheel or being
unable to brake properly. As for accidents involving running off the road, which have the highest fatal
accident rate of all accident types, 66% of these are caused by operating error violations, making this theirprimary cause. Although not much difference is seen in the composition rate for operating error accidents
with non-elderly drivers, it is known that there are differences in the content of the operating errors.(5) As
this indicates, patterns for legal violations vary due to a combination of the accident type and the locations
where they occurred.

12

ITARDA 20th Work Shop Report(2) Human negligence serving as causative factors for accidents
Legal violations by the party that caused the traffic accident are frequently cited as the cause for said
accidents. But it is commonly known that elderly drivers naturally engage in compensatory driving in orderto reduce the risk of accidents. However, these are often caused by human negligence, and as a result theviolation the driver perpetrated often leads to the accident.(6) Numerous items can be brought up when you
consider the causes attributable to human negligence that occur when driving a four-wheel vehicle. Here,the most common human factors leading to accidents caused by elderly drivers were divided up into a totalof seven items, as shown in Table. 1. These include intrinsic / extrinsic failure to pay attention forward andfailure to confirm safety factors, which lead to delayed detection of other vehicles, judgment errors that
tend to be influenced by cognitive decline, such as mistakenly assuming the other vehicle will yield to themor misjudging the speed of and distance to the other vehicle, as well as operating errors involving
mishandling of the steering or braking caused when their vehicle deviates from the lane it is traveling in.
Based on these causative factors, characteristics of elderly drivers will be considered.
Table 1. Causes attributable to human negligenceType of human factors among drivers

Delayeddetection

Judgment
errorsOperatingerrorsIntrinsic failure to pay
attention forward

Psychological / physiological factors (dozing off, being lost inthought, or other absent-minded driving, chatting)

Extrinsic failure to pay
attention forward

Causes accompanying actions (dropping something, distracted by
the scenery / other vehicles, etc.)

Failure to confirm safety
factors

Neglecting to confirm safety despite decelerating down to a speed
at which confirmation can be made and failing or being delayed in
detecting the other party

Failure to observe
surrounding traffic
movement

Detecting hazards but mistakenly thinking they pose no specificrisk or erroneously neglecting to pay attention to one’s
surroundings

Failure of prediction

Mistaken impressions while driving such as the speed of one’s own
vehicle and the speed of, distance to, and behavior of anothervehicle, erroneously thinking the other party is yielding

Traffic environment

Misapprehension or misidentification of the traffic environment,such as the road configurations or traffic regulations

Operating error

Making an operating error despite confirming the danger andtaking measures for it, or growing hesitant to take action based on
surprise / fright (steering error, misapplication of pedals, weak
braking)

Fig. 12 shows the composition rate for the number of casualty and fatal accidents by seven different humanfactors for each frequently-occurring and high fatality rate accident type, and each road configuration onwhich accidents frequently occur. In terms of the human factors for angle collisions and collisions whileturning left / right, which are the accidents that occur most frequently at intersections, more than 80% of

13ITARDA 20th Work Shop Reportthese were due to delayed detection. Of these, 70% consisted of cases where a failure to confirm safety
factors led to an accident. Examples of this include when the driver fails to confirm safety factors
immediately prior to entering an intersection or insufficiently confirms safety factors (which all constituteneglecting safety), despite the driver decelerating to a speed where they could confirm the presence ofanother vehicle. Specifically, it is commonly known that many of the elderly drivers who cause accidents
suffer from a narrower field of vision, decreased angle at which they can turn their head, or a decline intheir dynamic visual acuity as they get older. This decline in visual performance, which makes it harder todetect vehicles approaching from the sides, for example, is believed to be one of the major factors for theirfailure to confirm safety factors. As a result, it is understood that an exceptionally large number of cases
involve elderly drivers causing accidents because they failed to detect another vehicle until immediately
prior to the collision. With rear-end collision accidents that occur near intersections or at non-intersections,a larger rate of these are due to both an intrinsic and extrinsic failure to pay attention forward (such as from
distracted driving) out of the delayed detection category. There are also numerous cases in which judgment
errors, such as when a driver starts up their vehicle after misjudging the movement of the preceding vehicle,
lead to accidents. The same holds true for operating errors, such as drivers getting flustered for some reason
and misapplying the brake / accelerator pedals, or extending the braking distance as a result of weakly
applying the brake pedal. Conversely, this graph reveals that—as a general rule—operating errors accountfor a larger rate of the accidents that occur at non-intersections. Compared with non-elderly people, elderly
drivers had a larger rate of head-on collision and collisions with roadside structures caused by an intrinsic
failure to pay attention forward. As for accidents where they run off the road, operating errors served as afactor that caused them to deviate from their lane, and account for as much as 63% of these accidents. For
elderly drivers in particular, while they do not drive all that fast, the claim could be made that they cause
accidents as a result of multiple overlapping factors. These include delayed application of the brakes,
failing to cut the wheel, and other operating errors, as well as misjudging the size of curves, failure to pay
attention forward, and more. This is also thought to be influenced by the fact that elderly people, as
opposed to the non-elderly, have a higher rate of running off the road accidents attributable to operating
errors involving mistakes with braking and steering rather than a failure to pay attention forward. (7)14ITARDA 20th Work Shop Report■Intrinsic failure to pay attention forward ■Extrinsic failure to pay attention forward■Failure to observe surrounding traffic movement■Failure of prediction■Operating error

Delayed detection:
Judgment errors:
Operating errors:

Elderly
高齢者

11 7

70

非高齢者
Non-elderly

10 7

70

Angle collisions(intersections)

Collisions while Elderly
高齢者turning left /right(intersections) Non-elderly
非高齢者

Elderly
高齢者
Rear-end
collisions (nearintersections,Non-elderly
非高齢者
non-intersections/ straight roads)

Head-onElderly
collisions (non- 高齢者
intersections)42

Non-elderly
非高齢者

5

75

12

5

77

10

37

6 19

18

17

41

6

12

23

高齢者
Running off Elderly
the road(nonNon-elderly
非高齢者intersections)

20% 40% 60% 80% 100%
High fatality
rate accidents

15

31
20

20

9

27

9

31

13

48

8 8 1152

13 10 7 5

0%

Occurrence rate of casualty accidents

14

35

Collisions with
Elderly
高齢者
roadside
structures(nonNon-elderly
非高齢者intersections)180%Frequentlyoccurring accidents■Failure to confirm safety factors■Traffic environment

6

63
9

57

20% 40% 60% 80% 100%

Occurrence rate of fatal accidents(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger(excluding special vehicles, trams, and trains), 2007-2016)

Fig. 12. Occurrence rates of casualty / fatal accidents by human factor for each type of accident and roadconfiguration(3) Detailed breakdown of human factors
A more detailed breakdown of the human factors discussed in the previous section is shown in Fig. 13. This
discussion of the human factor items should be prefaced by the fact that it focuses on how a comparatively
large number of casualty accidents are caused due to human error by elderly drivers, and that the figuresindicated in the bar graphs represent the composition rate for the number of accidents that also include
other items as well.
Angle collisions and collisions while turning left / right are accidents that occur at intersections are mainly
caused by the delayed detection of the other vehicle. The majority of these accidents are due to a failure toadequately confirm safety factors, but it has also become apparent that some are due to a complete failure
to confirm safety factors. Even among road environments that are changing from moment to moment,intersections in particular are overflowing with an over-abundance of information necessary to travel
through them safely. They are locations where numerous human errors are prone to occurring, such as froma failure to observe traffic signs or hazards. In such locations that are at high risk of accidents occurring,
45-46% of accidents are due to a failure to confirm safety factors, potentially making this a point thatmerits scrutiny. As for collisions while turning left / right, the rate of these caused by a failure to pay
attention when there is no specific threat in particular is 10%, which is no small figure. This suggests that
determinations based on mistaken assumptions are potentially leading to accidents. While rear-end collision
accidents are caused by a number of different factors, compared with non-elderly people a large rate ofsuch accidents involving elderly drivers are caused by failing to apply the brakes with enough force. This ispresumably also affected not only by their sense of inter-vehicular distance with the preceding vehicle, but

15

ITARDA 20th Work Shop Report

also by the decline in the physical strength of their legs as well as their mental agility. Conversely, Fig. 12
showed that head-on collisions, which have a high fatal accident rate, are oftentimes caused by an intrinsic
failure to pay attention forward. The rate caused by being lost in thought and other forms of carelessdriving of 31% is large compared with that of non-elderly people, on top of which 12% are due to dozing
off. When drivers get lost in thought they neglect to confirm safety factors up ahead of them. It is believedthat even though elderly drivers do not drive excessively fast, they fail to realize when their vehicle
deviates into the oncoming traffic lane, causing them to collide with oncoming vehicles. This holds true not
only on curved roads, but on straight ones as well. Conversely, compared with accidents at intersections,these accidents are characterized by the fact that most of them are attributable to improper steering fromamong the operating error category. Collisions with roadside structures share the same properties as thecauses for head-on collision accidents that occur when a driver deviates from their lane. However, there
tends to be a larger rate of these attributable to steering operating errors as opposed to head-on collisions.
Absent-minded driving
漫然運転

Distracted
by scenery, other vehicles, etc.
景色・他車等に脇見Dropped / picking up something
物を落した/拾うFailureto confirm safety factors
安全確認なしFailureto adequately confirm safety
安全確認不十分
factors
ペダル踏み違い
Pedal misapplication

Inattention from lack of danger
危険性なく不注視

Dozed off
居眠り

Weak braking
ブレーキ弱いSteering
errors
ハンドル操作不適

Elderly
高齢者

11

25

45

Non-elderly
非高齢者

9

24

46

Angle collisions(intersections)

Collisions whileturning left / right(intersections)Head-onElderly
collisions (non- 高齢者
intersections)Non-elderly
非高齢者

高齢者
Elderly

29

46

10

Non-elderly
非高齢者

28

50

8

Rear-end
Elderly
高齢者
collisions (nearintersections, non非高齢者
Non-elderlyintersections/straight roads)

0%

31

17

17

4 4

19

11

16

15

7 4

22

7

21

Collisions
Elderly
高齢者with roadsidestructures
Non-elderly
非高齢者(nonintersections)

Elderly

12

高齢者
Running off
the road (non非高齢者
intersections) Non-elderly

13

22
13

9

22
32

7

9
13

19

41
41

6

5

7
42

0% 20% 40% 60% 80% 100%20% 40% 60% 80% 100%

Occurrence rate of fatal accidents

Occurrence rate of casualty accidents
High fatality
rate accidents

Frequently-occurring
accidents(Primary party: Medium- + small-sized motor vehicles, Secondary party: Mopeds and larger(excluding special vehicles, trams, and trains), 2007-2016)

Fig. 13. Occurrence rates of casualty / fatal accidents by detailed human factor for each type of accident and roadconfiguration

While misapplications of the brake and accelerator pedals account for a small rate at 5%, this graph reveals
that this is a causative factor not observed among non-elderly people. This also reveals that a larger
percentage of running off the road accidents are attributable to steering operating errors and misapplicationof the pedals than with head-on collisions and collisions with roadside structures. While there is nodifference in the rate caused by operating errors between elderly and non-elderly drivers, there is a drastic
difference in the percentages for the different danger perception speeds at the time accidents occurred asshown in Fig. 8. Therefore, even though the operating error is the same, it seems that the circumstances aredifferent.

16

ITARDA 20th Work Shop Report(4) Conditions when accidents by elderly drivers occur (microdata analysis)
Based on the human error factors among elderly drivers discussed up through the previous section,
cognitive judgment error samples were deduced for 206 accidents and 371 items from among the micro
accident survey data for the past ten years from 2006 – 2015. Then the results of interviews with elderly
drivers for each accident type and each cognitive judgment error from right before an accident with acomparatively high composition rate occurred were analyzed. The results of this are shown in Fig. 14.
Looking at this by the major brackets here reveals that most of the cases involved accidents caused when
the driver failed to pay attention to the traffic environment in particular, with these accounting for 42% of
the total. This also indicates that a great deal were due to a decrease in concentration, which is interlinked
with intrinsic factors, at 20%, as well as obstructed vision (including delayed detection of the other vehicle
due to poor visibility) at 15%. First off, the item “Not paying particular attention” included familiarity withroutine driving, with respondents saying things like “I thought the road was deserted, so I never expected a
car to come from the side” and “Because it’s a road I’m familiar with that I drive all the time.” This
familiarity makes it harder to recognize changes in the traffic environment, and produces carelessness on a
grand scale. In other words, given their long years of driving experience, these drivers internalize a form of“habituated driving” in which they drive automatically without conscious awareness. This suggests thatawareness of circumstantial changes is perhaps something that declines without the person being
consciously aware of it.
Rear-end collisions (near intersections &Head-on collisions / collisions with roadside

正面/工作物衝突/路外逸脱(単路)structures / running off road (non-intersections)

追突(交差点付近&単路/直線)
non-intersections/straight roads)

Angle collisions & collisions while turning left /出会い頭&右左折(交差点)right (intersections)15
Decreased concentration(intrinsic)

Composition rate (%)

20%[The figures show the composition rate for said accidents out of the total](Extrinsic) Distracted
driving

4%

11%

ObstructedvisionNot paying particularattention

Driving
interference

15%

42%

7%

10

5

0

Human factors with a relatively high composition rate
(Primary party：Medium- + small-sized motor vehicles, Secondary party: Four-wheel vehicles(excluding special vehicles and mini cars), micro accident data from 2006-2015)

Fig. 14. Results of interviews with elderly driving party by human factor for each accident type17

ITARDA 20th Work Shop Report

Moreover, based on an analysis of the results of interviews with the parties to accidents, one characteristic
they are presumed to have is that the accidents occurred while the driver was unable to do anything to avoid
them, either from failing to recognize the other party or from being unable to take evasive action despite
recognizing the danger. Examples of this include responses like “I was completely unaware of the othervehicle until we crashed” and “I got flustered and couldn't do anything.” While items dealing with taking
medication and sudden illness have small composition rates among the decreased concentration (intrinsic)
items, they lead to accidents and are considered to be characteristic of elderly drivers. There are also a
comparatively large number of cases in which drivers got into accidents because they were driving by
falling back on customary habits as they normally do despite the fact that they were in an unsafe situation,such as a road environment with poor visibility around an intersection on account of obstructed vision.
Now then, the question is how do drivers find themselves in such situations? We will take a look at this byusing behavioral error models for elderly drivers, who are prone to causing accidents, in the next section.

5.

Causative factors for accidents by elderly drivers(1) Driving behavioral model
A general driving behavioral model for driving a vehicle safely is shown within the box with the dotted line
in Fig. 15. This involves instantaneously ascertaining information needed to drive safely based on a large
volume of information taken in from outside. This includes information on the traffic environment, which
is changing from moment to moment, as well as on the natural environment, such as the conditions of andweather along the roads they are driving. It also involves detecting and recognizing hazards andinstantaneously making decisions on the extent to which they should respond in their own driving and thetiming for this, then taking the appropriate response. In addition, drivers must continue to drive safely bypromptly and perpetually rotating through this cycle based on information provided as feedback and thevarious environmental information all around them. Drivers must fully utilize their own physical functionin order to do this. But with elderly drivers it is assumed that they get into accidents because they are nolonger able to smoothly rotate through this “Perceive – Decide – Act” cycle due to their reduced physicalfunction as a result of aging. For example, they tend to overlook hazards and signs or make judgment errors
as a result of said decline, rendering them incapable of skillfully tying this in with their subsequent actions.
Illnesses and other such factors further exacerbate the impact on safe driving.

18

ITARDA 20th Work Shop Report

Feedback(correct action / conduct)
フィードバック(操作・行動修正)
Traffic
environment

Predict
danger
危険予測

Road
交通環境
environment

Perceive
認知Decide判断

Act操作

environment

自然環境

Awareness,
perception
知覚,認知Learning,
memory学習,記憶Motorfunction
運動機能(Vast amount of(膨大情報)
information)

Information
processing
情報処理

Ability
to execute
遂行機能

Motioncontrol
運動制御· Eyesight (visual acuity /・視覚(視力・視野)
visual field)
・注意,集中力· Attention,
concentration· Frontal cortical function·・バランス機能
Balance function· Risk response· Driving learning· Understanding,memory・理解,記憶力· Knowledge of trafficlaws
・道交法知識· Driving experience

Delayed / erroneous detection
発見の遅れ/誤り

Delayed / erroneous actions
Delayed / erroneous decisions 操作遅れ/誤り
判断の遅れ/誤り

Failing to see lights / signs
・信号/標識見落し

Misinterpretations
・勘違い

道路環境
NaturalPhysical身体機能
function

Examplesof the impact that the
高齢による身体機
decline of physical function
能低下に伴うresulting from aging has interms of causing accidents

Failing to see vehicles /事故発生の影響例 ・車両/歩行者見落し

pedestrians
Careless driving / insufficient・漫然運転/確認不足
confirmation

・前頭葉機能・リスク対応Driving sensory errors
・運転感覚誤りRoad configuration errors
・道路形状誤りSafe
安全driving

走行

・運転学習

・運転経験

Operating errors
・操作ミス
Failing to quickly cut the wheel
急ハンドルや切り損ね
Misapplication of the pedals
Applying
insufficient force to
ペダル踏み間違いpedal

ペダルを踏む強さが不適

Effects may be magnified due
to age, illness, alertness level,影響拡大
or fatigue
加齢,疾患,覚醒水準,疲労でFig. 15. Driving behavioral model and the effects of aging(2) Unsafe driving behavioral model characteristic of elderly drivers
There are case examples to be found among those elderly drivers who caused accidents in which they were
driving a vehicle they were unfamiliar with, such as driving the family car or switching over to a new car.
However, one frequently hears comments from the parties to accidents like “I got flustered” and “Before I
knew it I had caused an accident” in recent accident reports. The question of why elderly drivers are nolonger able to smoothly rotate through the behavioral model for safe driving will be considered based on
the behavioral model for unsafe driving characteristic to elderly drivers who cause accidents that is shownin Fig. 16. As a result of the decline in physical function that accompanies aging, elderly drivers may bereceiving less of various types of information obtainable from the outside world as a result of a narrowingof their visual field, for example, which can lead to a lack of information that by nature is crucial for safe
driving. What is more, declining capabilities when it comes to attentiveness, comprehension, and so forth
further reduces the amount of information they can take in. Therefore, the thinking is that errors and delays
in judgment occur, which produce imperfect situations when it comes to predicting danger, such as drivers
being unable to pick up on some of the information needed in order to drive their vehicle safely. In addition,elderly drivers have a particularly pronounced tendency to make decisions after their own fashion by
relying on the habits they have accumulated over their many years of driving experience. This reduces theirability to properly make decisions and respond according to the traffic environment, which changes frommoment to moment, and therefore increases the risk of accidents occurring.

19

ITARDA 20th Work Shop Report

Contraction ofvisual field視野狭窄
Failureto predict danger
危険予測不全交通

Traffic
environment
環境
information

情報

Perceive
認知Reduced volume of
情報量縮小
information

Decide
判断

Overlooking
見落し

Act
操作

遅れ,誤り

Delays, errors

動体/深視力 前頭葉機能

Kinetic vision/ depth perception Prefrontal cortical function
Risk response function

Attention / concentration

Drive
走行

注意/集中力 リスク対応機能
Individualistic

Understanding / memory

decision-making reliant on
理解/記憶力 習慣依存の自己流判断
habitsBalance function
バランス機能Driving learning

運転学習機能function
Declinein physical
身体機能低下functionContraction ofvisual field視野狭窄(A) Information
processing load needed to drive safely(A)安全運転に必要な情報処理負荷

事故

Accident

交通

Traffic
environment
環境
information

情報

Decide
操作
判断

Perceive
認知Reduced volume

情報量縮小
of information

Delays, errors
遅れ,誤りOverlooking
見落しKinetic vision/ depth perception Prefrontal cortical function

動体/深視力 前頭葉機能
Risk response function

Attention / concentration

注意/集中力リスク対応機能Understanding/ memory
Individualistic
decision-making reliant
理解/記憶力 習慣依存の自己流判断
on habits

Thinking/ emotional control
思考/感情抑制Act
操作

Balance function
バランス機能Driving learning

function
運転学習機能Declinein physical
身体機能低下function(B) Non-driving information processing load
(B)運転以外の情報処理負荷

Lost in thought / chatting/ distracted / emotional (angry, flustered, panicked), etc.
考え事/雑談/脇見/感情(怒り,慌て,パニック)等

Fig. 16. Unsafe driving behavioral model for elderly drivers

Given such conditions, when a totally unexpected phenomenon suddenly occurs—such as when one’s
vehicle juts out into the oncoming vehicle lane and collides with another car—the situation changes to theaccident occurrence model shown in the model diagram on the bottom. The information processing load(B) required for emotional control exerted in an effort to suppress thoughts not related to driving, such as
those when something unexpected has happened, as well as to suppress one’s surprise and sense of being
flustered, suddenly soars. As a result, the information processing load (A) which they need to drive safely
plummets, and they are unable to respond by avoiding danger, let alone realizing that they are still driving
incorrectly. Accidents occur when (B) exceeds (A) and the capacity that can be handled by theirinformation processing faculties (which have declined with age) overloads. When the load condition for (B)further surpasses that of (A), major accidents occur. In other words, conclusions that can be drawn fromthis include the fact that the capacity for the information that elderly drivers can process in the moment
declines as they age, their information processing load balance can easily become significantly tilted tothinking / emotional control, and their driving skills that have become habituated and which have never led

20

ITARDA 20th Work Shop Reportthem to cause an accident over a long period of time can make them overconfident in their driving, thereby
giving rise to accidents.

(3) Model for accidents occurring due to operating errors by elderly drivers (5)It was previously mentioned how elderly drivers tend to drive relatively more safely compared with
non-elderly drivers through compensatory driving and the like. But it is also commonly known that the
decline in physical function that accompanies aging produces inconsistencies between one’s intentions andactions, which can lead to operating errors. Therefore, an example of an accident occurrence model for thepedal misapplication operating errors characteristic of elderly drivers (which cause accidents with high fatal
accident rates among elderly drivers) is shown in Fig. 17. When it comes to driver conduct for driving
safely, based on the information processing model required for safe driving behavior, the traffic and roadenvironment situation and various other data needed to continue driving safely is taken in cognitively
through one’s sensory functions in the form of information. This activates “driving schema,” and results indriving that occurs in accordance with sensorimotor patterns unconsciously and automatically. Since
drivers with a long track record of driving experience are more used to driving, normally when they drive
they do so without being consciously aware of the act itself all that much. However, the thinking is that,should some sort of error occur with this driving schema, this will lead directly to operating errors andtherefore cause accidents. As shown in the figure below, errors in the schema for applying the brake pedal,
such as mistakenly applying the accelerator pedal instead of the brakes for example, are thought topotentially occur as shown below (excluding cases caused by physical functions, such as declining leg
strength).
Attention resources featuring limited
capacity (C) due to aging(A) Emotional state(impatient, flustered)

Information
processing capacity
overload
C < A+B
Feedback

A>>B
Recurrence error(B) Corrective operations

Sensory
information
input

Accident
prevention

Schema for
applying pedals

Sensorimotor
pattern

Unconscious / automatic

Initiate reaction

Reaction system
Apply pedal

Feedback
Effects may be magnified due to illness, alertness level, fatigue, or aging(SRK Model (Rasmussen, 1986) Modified)Pedal
misapplication
accident

Fig. 17. Example of an accident occurrence model resulting from operating errors by elderly drivers

・ The intention to step on a pedal alone activates, and the driver intends to apply the brake pedal locatedon the left-hand side. However, they actually end up applying the accelerator pedal, which is locatedslightly to the right from the center of the driver’s seat.

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ITARDA 20th Work Shop Report

・ The driver has erred in assessing the situation and instead applied the accelerator pedal, when thesituation inherently should have involved applying the brake pedal.
・ While the driver intended to apply the brake pedal, since this is similar to the situation whereby theynormally apply the accelerator pedal, they instead ended up applying the accelerator pedal.
Even if the driver makes a mistake in applying the pedals, when they only have a small load of informationthat must be processed regarding the driving environment and their own emotional state, then they can takesome sort of corrective action. An example of this would be realizing right away that they made anoperating error, thereby working to correct their actions by devoting attentional resources to their own
driving, and then taking their foot off the accelerator pedal. It is safe to assume that most elderly drivers
have previously had experiences like where they have pressed the accelerator then pulled their right foot off
the pedal when they accelerated faster than they meant to. Or where they made a mistake when shifting
gears and started moving forward when they meant to go in reverse, figured out what was happening rightaway, and took their right foot off the accelerator. However, while this happens to non-elderly drivers as
well, for most elderly drivers when an unexpected phenomenon occurs, such as a schema error leadingthem to misapply the pedals and sending their vehicle shooting out of control, this can induce emotional
states such as desperation and cause them to get flustered. When this happens, most of their limited
attention resources (C) are devoted to processing their emotions (A) and cannot be used for correcting theirdriving (B). So when this schema remains uncorrected once it has been activated, the act of pressing theaccelerator pedal once more continues to be repeated over again. Oftentimes these sorts of human errors areespecially dominated by the habits we have internalized and occur unconsciously and automatically, andtherefore it is difficult for the driver to prevent them through their own efforts alone. With elderly drivers,
the capacity and processing functions they need to process information decline as they get older. As such,they require countermeasures from the external environment, such as the Safety Support Car S Wide, eventhough these cannot handle every scenario.

6.

Reducing accidents by elderly drivers(1) Improvements for reducing the risk of accidents without being overly-reliant on
long-standing driving habits
・ Enhancing danger prediction and avoidance skills in a hands-on manner that people will not tire of・ Fun learning designed to improve skills
Improving danger prediction capabilities that are not dependent upon driving habits is important when it
comes to getting drivers to drive their vehicles safely. Elderly drivers have a tendency to drive by relying
on their long-standing driving habits, and so they must be made self-aware of the decline in their own
physical function and the extent to which this has occurred. At present, opportunities for elderly drivers totake driving training courses have been established in law when they renew their driver’s licenses. In
addition to these, there are also opportunities where they can have their driving skills objectively evaluatedthrough practical skills training and driving practice simulators. But it is conceivable that many elderly

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ITARDA 20th Work Shop Report

drivers who are self-confident when it comes to their driving will refrain from taking up these sorts ofopportunities, perhaps because they tend to think that they are fine unless strongly prompted to thinkotherwise for some reason. Therefore, it will perhaps be necessary to devise ways to enhance elderly
drivers’ danger prediction and risk avoidance skills in a manner suited to various places and settings. Thiscan be done by, for example, developing and popularizing fun learning apps that can instill drivers withawareness and consciousness while they have fun learning with a simple game feel that they can play athome and which they won't tire of by utilizing VR technologies that combine together technologies likesmartphones and simple goggles.

(2) Further improving the road traffic environment
・ Substantially reducing the volume of information that must be processed while driving
・ Installing / establishing road sign designs with outstanding visibility suited to the physical characteristics
of elderly people
Ideally, further improvements are expected be made to the road traffic environment in order to reduce thevolume of external information that must be processed while driving and enable drivers to properly rotate
through the safe driving cycle. Examples of this include improving the visibility of road signs that aresuited to the physical characteristics of elderly drivers to ensure that they do not overlook or misjudge them,as well as designing intersections in which traffic does not intersect.

(3) Popularizing the Safety Support Car S and advancing driving support technology
・ Understanding the effectiveness of the Safety Support Car S and proactively introducing it to the market
・ Setting in place an environment for boosting elderly people’s motivation to purchase safety vehicles
・ Advancing Human Machine Interface (HMI) driving support technology
Currently, government agencies, local governments, JAF, auto manufacturers, and others are working
together to hold hands-on test drive sessions for the Safety Support Car S all around the country. The factthat drivers are being given the chance to actually drive these cars and experience their positive aspects isoutstanding. However, many elderly drivers still do not fully understand the effectiveness and advantagesof the Safety Support Car S, while there are presumably a great many of them who do not even know the
first thing about it. The hope is that activities to promote the popularization of safety vehicles will be
carried out in striving to boost elderly people’s motivation to purchase them. In particular, the hope is that
the Safety Support Car S Wide (which is equipped with a lane-deviation warning system) shown in Table 2
will be introduced to the market and the market for this will be expanded from an early date in order toreduce accidents from running off the road, collisions with roadside structures, and head-on collisions,which carry a particularly high fatal accident rate. In conjunction with this, the hope is that driving support
technologies centered around HMI will be advanced, with consideration given to typical accidents caused
by elderly drivers.

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ITARDA 20th Work Shop Report

Table 2. Ancillary functions equipped on the Safety Support Car S
Symbolマーク

Description
内容
Support Car S Basic
サポカーS
ベーシック
· Automaticbraking
at low speeds (versus oncoming vehicles)· Acceleration
control
device for when the pedals are misapplied
・低速自動ブレーキ(対車両)

・ペダル踏み間違い時加速抑制装置
SupportCar S Basic+
サポカーS
ベーシック+· Automatic braking (versus oncoming vehicles)· Acceleration
control device for when the pedals are misapplied
・自動ブレーキ(対車両)

・ペダル踏み間違い時加速抑制装置
SupportCar S Wide
サポカーS
ワイド
· Automatic braking (versus oncoming pedestrians)
・自動ブレーキ(対歩行者)· Acceleration
control device for when the pedals are misapplied· Lane deviation warning device
・ペダル踏み間違い時加速抑制装置· Advanced
lights・車線逸脱警報装置
・先進ライト(4) Promoting research into the special characteristics of elderly drivers
・ Research into quantitatively assessing driving characteristics that come about as a result of declining
physical function
・ Research into human characteristics designed to improve information processing faculties
・ Investigating measures to prevent accidents from a psychological dimension
It is strongly hoped that various research institutes will promote human research on not only physicalfunction, but also the psychological characteristics unique to elderly people, in order to cut down on
accidents by elderly drivers.

Conclusion
As the population of elderly people continues to rise in the future, we must succeed in further reducing thenumber of fatal accidents. For this, there are incredibly high hopes that the achievement of autonomousvehicles will be effective at preventing traffic accidents by compensating for the driver’s cognition anddecision-making, as well as their operating errors. However, the time when all vehicles on the market comeequipped with self-driving technology is still off in the distant future. When this is taken into consideration,
it is conceivable that new accidents will occur under a traffic environment in which vehicles equipped with
cutting-edge safety technologies and ordinary vehicles are intermixed. As such, it is important that all
drivers have a strong sense of safety awareness prompting them to absolutely avoid causing accidents
without being bound by their own distinctive driving habits, in order for Japan to achieve the world’s safest
road traffic environment.

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ITARDA 20th Work Shop Report

参考文献(1) 石川敏弘：自動車における車線逸脱の要因分析,(財)traffic accidents 総合分析セン
ター研究報告書,ITARDA H22-04, 2011(2) 柴崎宏武：最近の traffic accidents の実態と特徴分析,自動車技術 Vol.71, No.4,
p.26-33, 2017(3) 松浦常夫：高齢ドライバーの安全心理学 第 3 章,東京大学出版会，2017(4) 柴崎宏武：elderly drivers による traffic accidents の現状, 法律のひろば P.24-33,
Vol.70/No.5, 2017(5) 柴崎、小菅、平川：traffic accidents データからみた elderly drivers accidents の特徴,
自技会秋季大会学術講演予稿集，自技会, 2017(6) 田久保宣晃：traffic accidents データによる運転者のヒューマンエラーと心的負荷の一考察, IATSS Review vol.30, No.3, P.23-23, 2005
(7) ITARDA：運転操作の誤りを防ぐ, イタルダインフォメーション No.107, 201425