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本部・東京交通事故調査事務所〒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.136

つくば 交通事故調査事務所

10

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ITARDA INFORMATION
交通事故分析レポート No.136lSpecia Accidents from collisions between four-wheel vehicles
feature turning right and four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles
is eﬀective for avoiding accidents ~Roughly 80% of such accidents occur due to a delay in noticing the oncoming vehicle
100％

Composition rate

No.136

公益財団法人 交通事故総合分析センター
令和2年 月 〒101 0064 東 京 都 千 代 田 区 神 田 猿 楽 町 ２ ７ ８(Masanori Taniguchi)

ITARDA INFORMATIONThis issue took a look at why accidents between a vehicle turning right and a vehicle going straightoccur and the sorts of countermeasures that are effective for combating them. The majority of thesetypes of accidents occur due to a delay in noticing the oncoming vehicle going straight by the driver ofthe vehicle turning right. The three factors below serve as the main causes giving rise to this delay innoticing the other vehicle, and it is important that we once again recognize the difficulty inherent inmaking right turns.
・ The increased complexity of making confirmation due to the wide angle needed to confirm it wassafe at the intersection made it difficult to sufficiently confirm that it was safe・ The presence of blind spots and a large number of lanes engendered a mistaken impression in thedriver that there were no oncoming vehicles going straight approaching and they neglected toconfirm that it was safe
・ A sentiment of rushing through the right turn so as to follow after the vehicle before themengendered in the driver the mistaken impression that the previous vehicle had already provided apriori confirmation that it was safe and they neglected to confirm that it was safe
Countermeasures include:
・ Improve the awareness / behavior of the driver of the vehicle turning right: They must repeatedly goback and forth between checking the lane of oncoming vehicles going straight, the area beyond theright turn, and then the lane of oncoming vehicles going straight again. They must then thoroughly
ensure that they proceed into the intersection without rushing the right turn, such as by coming to atemporary stop or moving at very low speeds.
・ Assistance from the road environment: Shift right-turn lanes closer to the oncoming vehicle lane
and adopt traffic signals equipped with right turn-only signs (right arrows) primarily for intersections
with a large number of lanes.
・ Assistance from vehicle technology: Practically implement and adopt cutting-edge safety
technologies such as warnings via sensor detection, damage mitigation brakes suited to handlingcollision accidents while turning right, and advance warnings through the use of signals between
vehicles and the between road and vehicles.
Combining and disseminating the countermeasures listed above in an effective manner can be
expected to prevent a delay in noticing other vehicles on the part of drivers, and could help to further
reduce accidents between vehicles turning right and vehicles going straight.

交通事故分析レポート

5 Conclusion

イタルダ インフォメーション

80％

21.1

0.1
0.5

60％
40％

1.2

12.3
11.2

12.4

0.1

24.7

Other
Errors in judgment
Delay in noticing(failure to conﬁrm
safety factors)
Delay in noticing(failure to conﬁrm
what is up ahead)

53.3

56.0

Head-on collision（n＝95,988）

Rear-end collision（n＝1,942,032）

12.4
Collision between a vehicle
turning right and a vehicle
going straight*1

Operating errors

6.8

65.9

20％
0％

22.1

（n＝123,680）

Human factors on the part of the primary party
for vehicle-vehicle accidents between four-wheel vehicles[Road Traﬃc Accident Statistics (2009 - 2018)]*1. Failure to pay attention to what is up ahead includes failing to notice due to being distracted or absentminded, while failure to conﬁrm safety factors includes
failure to notice due to not checking to ensure safety or failure to notice due to insuﬃciently checking to ensure safety. Errors in judgment refer to human factors
such as misjudging the distance to or speed of the other vehicle, or a driver failing to pay attention due to the thinking that the other vehicle would yield to them.

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Causes of collision accidents between four-wheel vehicles turning right2 and four-wheel vehicles going straight

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did a delay in noticing an oncoming vehicle going straight occur
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on the part of the vehicle turning right?

against the delay in noticing oncoming vehicles ・4 Countermeasures
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going straight and their expected results

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Accidents from collisions between four-wheel vehicles turning rightand four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles is effective for avoiding accidents ~1 Introduction

In addition, when viewed in terms of trends by age group, the human factors by age group for those age 65 and older (elderly
people) and those age 64 and younger exhibit largely identical composition rates (Fig. 1). This reveals that the causal factors
behind the occurrence of accidents between a vehicle turning right and a vehicle going straight are commonly shared irrespectiveof the age group.

The number of traffic accidents (casualty accidents) has been on a downward trajectory year by year. However, the fact still
remains that the number of accidents that occur in a single year exceeds 380,000 accidents (2019), and many people still fallvictim to such traffic accidents.
Given this state of affairs, in recent years fatal accidents due to pedal misapplication, fatal accidents involving pedestrians causedby collision accidents between a four-wheel vehicle turning right and a four-wheel vehicle going straight, and other such accidents
have had enormous societal repercussions. There have even been some accidents that the media and others have chosen to
spotlight, and which have received several days worth of ongoing coverage.
This issue will analyze collision accidents between a four-wheel vehicle turning right and a four-wheel vehicle going straight, as
this is a type of accident in which there is enormous social interest, out of a desire to look at their characteristics and trends.
Analytical results on collisions while turning right between a four-wheel vehicle and a motorcycle and accidents between
four-wheel vehicles and bicycles / pedestrians were covered in ITARDA Information No. 91 and No. 95, and readers areencouraged to look at these as well.
Taking a look at the actual circumstances surrounding vehicle-vehicle accidents between four-wheel vehicles (Table 1) reveals
that accidents between a vehicle turning right and a vehicle going straight are always the most highly ranked accident type ineach category *2, and thus represent a challenge. So then the question is: Why do collision accidents between a four-wheel
vehicle turning right and a four-wheel vehicle going straight occur and what sorts of countermeasures are effective against them?
By using Road Traffic Accident Statistics from 2009 - 2018 (hereinafter referred to as "macrodata") and in-depth case studies(hereinafter referred to as "microdata"*3), this issue will take a look at casualty accidents between a vehicle turning right and avehicle going straight (hereinafter referred to as "accidents between a vehicle turning right and a vehicle going straight").
*2) Number of casualty accidents = Total number of fatal, serious injury, and slight injury accidents; Number of fatal and serious injury
accidents = Total number of fatal and serious injury accidents
Share of fatal and serious injury accidents (%) = Number of fatal and serious injury accidents / Number of casualty accidents × 100*3) With regards to the analytical results from the microdata, attention must be paid to the impact that the number of data points hason the accuracy.

Table 1. Number of accidents by type of accident between four-wheel vehicles
and the share of fatal and serious injury accidents [macrodata (2009 - 2018)]
Number of casualty accidents

Number of fatal andserious injury accidents

Share of fatal andserious injury accidents (%)① 20.0

Head-on collision④

95,988② 19,224

Rear-end collision① 1,942,032③ 19,217

1.0

Crossing collision②

640,099① 29,167③ 4.6

22,031

446

2.0

③

123,680④ 8,537② 6.9
2.2

Collision while turning left
Collision between a vehicle turning right /Collision whileoncoming vehicle going straightturning right

38,490859

Collision while passing or overtaking

26,383712

2.7

Collision while passing each other

30,838

1,099

④ 3.6

Other

283,024

5,914

2.1

Other

ITARDA INFORMATION no.136

0.2

100％

Composition ratelSpeciafeature

80％

22.1

0.4

0.1
20.8

0.5

Operating errors

60％
40％

65.7

65.9

11.5

12.7

Age 65 and older（n＝27,298）

Age 64 and younger（n＝96,382）

20％
0％Causes of collision accidents between four-wheel vehicles

Table 2 shows the numbers for collision accidents between four-wheel vehicles turning right and four-wheel vehicles goingstraight by their causes by what factors are at play from the perspective of causes attributable to human factors, factors with theroad environment, or vehicle factors. It also shows the share out of the total number of casualty accidents that these account for.
This reveals that the majority of these were attributable to human factors, with only a small fraction of each attributable to roadenvironment-related factors or vehicle-related factors.
Next, looking at the human factors involved in accidents
Table 2. Number of collision accidents between
between a vehicle turning right and a vehicle going straightfour-wheel vehicles turning right and four-wheelfrom the graph on the front cover (composition rate by humanvehicles going straight by factors attributable to thefactor of the primary party) shows that the most common
primary party and the share of the total number offactor behind collision accidents between a four-wheel vehicle
casualty accidents these account for
turning right and a four-wheel vehicle going straight was a
failure to confirm safety factors that led to a delay in noticing,which accounted for two-thirds of the whole. A common factor
Number of accidents
Share (%) *4
with head-on collisions and rear-end collisions is a failure to
Human factors at play
123,524
99.9
pay attention to what is up ahead, which stands in starkRoad
environment-related
factors
at
play
2,526
2.0
contrast with the fact that a failure to confirm safety factors is
uncommon. In addition, with accidents between a vehicle
Vehicle-related factors at play108
0.1
turning right and a vehicle going straight, a failure to confirm[Macrodata (2009 - 2018)]
safety factors and a failure to pay attention to what is up ahead
combined account for nearly 80% of the total. This reveals that *4) Share by cause (%) = Number of accidents by each cause / 123,680
a delay in noticing oncoming vehicles as a result of these two(total number of casualty accidents out of accidents between afactors serves as the primary cause of such accidents.
vehicle turning right and a vehicle going straight) × 100
ITARDA INFORMATION no.136

Errors in judgment
Delay in noticing(failure to conﬁrm
safety factors)
Delay in noticing(failure to conﬁrm
what is up ahead)Fig. 1. Human factors on the part of the primary party by age group for collision accidents
between a four-wheel vehicle turning right and a four-wheel vehicle going straight[macrodata (2009 - 2018)]

Next, Fig. 2 shows collision accidents between a four-wheel vehicle turning right and a four-wheel vehicle going straight by thelocations where they occurred. Intersections accounted for just under 90% of the total, with more than 70% of these occurring at
signalized intersections.
At intersections, there are numerous other entities that get involved in accidents from collisions while turning right aside fromoncoming vehicles, including crossing pedestrians, bicycles, and other vehicles beyond the right turn. In addition, it is believedthat the fact that cases where there are a large number of lanes at signalized intersections and the large number of entities in andof themselves due to traffic congestion increases the share of accidents that occur there. It will presumably be important toenable drivers to quickly notice dangers from among the many entities found at intersections for the sake of avoiding accidents.
But when it comes to accidents between a vehicle turning right and a vehicle going straight, what are the original causal factorsthat give rise to this delay in noticing oncoming vehicles, such as a failure to confirm safety factors?

2.0%

10.1%

0.3%
Intersection - Signalized[The numbers in circles in Table 1 indicate their rank from the top-ranked entry for each category (excluding “Other”)]

2 turning right and four-wheel vehicles going straight

Other

Intersection - Non-signalized

15.8%
71.8%

Near an intersection
Uninterrupted road section
Other（n＝123,680）

Fig. 2. Locations where collision accidents between four-wheel vehicles
turning right and four-wheel vehicles going straight occurred [macrodata (2009 - 2018)]

Why did a delay in noticing an oncoming vehicle going
3 straight occur on the part of the vehicle turning right?
■ When did the driver notice the oncoming vehicle going straight?

From here on, we will take a look at the main causes behind the drivers' delay in noticing oncoming vehicles going straight byfocusing on accidents caused by the drivers of vehicles turning right involved in accidents between a vehicle turning right and avehicle going straight from the microdata between 2009 and 2018. First, it is the author's intention to begin by ascertaining thepoint where the driver first noticed the other vehicle. When did the driver of the vehicle turning right first notice the oncoming
vehicle going straight and when did they collide with them?
ITARDA INFORMATION no.136

Accidents from collisions between four-wheel vehicles turning rightand four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles is effective for avoiding accidents ~1 Introduction

In addition, when viewed in terms of trends by age group, the human factors by age group for those age 65 and older (elderly
people) and those age 64 and younger exhibit largely identical composition rates (Fig. 1). This reveals that the causal factors
behind the occurrence of accidents between a vehicle turning right and a vehicle going straight are commonly shared irrespectiveof the age group.

The number of traffic accidents (casualty accidents) has been on a downward trajectory year by year. However, the fact still
remains that the number of accidents that occur in a single year exceeds 380,000 accidents (2019), and many people still fallvictim to such traffic accidents.
Given this state of affairs, in recent years fatal accidents due to pedal misapplication, fatal accidents involving pedestrians causedby collision accidents between a four-wheel vehicle turning right and a four-wheel vehicle going straight, and other such accidents
have had enormous societal repercussions. There have even been some accidents that the media and others have chosen to
spotlight, and which have received several days worth of ongoing coverage.
This issue will analyze collision accidents between a four-wheel vehicle turning right and a four-wheel vehicle going straight, as
this is a type of accident in which there is enormous social interest, out of a desire to look at their characteristics and trends.
Analytical results on collisions while turning right between a four-wheel vehicle and a motorcycle and accidents between
four-wheel vehicles and bicycles / pedestrians were covered in ITARDA Information No. 91 and No. 95, and readers areencouraged to look at these as well.
Taking a look at the actual circumstances surrounding vehicle-vehicle accidents between four-wheel vehicles (Table 1) reveals
that accidents between a vehicle turning right and a vehicle going straight are always the most highly ranked accident type ineach category *2, and thus represent a challenge. So then the question is: Why do collision accidents between a four-wheel
vehicle turning right and a four-wheel vehicle going straight occur and what sorts of countermeasures are effective against them?
By using Road Traffic Accident Statistics from 2009 - 2018 (hereinafter referred to as "macrodata") and in-depth case studies(hereinafter referred to as "microdata"*3), this issue will take a look at casualty accidents between a vehicle turning right and avehicle going straight (hereinafter referred to as "accidents between a vehicle turning right and a vehicle going straight").
*2) Number of casualty accidents = Total number of fatal, serious injury, and slight injury accidents; Number of fatal and serious injury
accidents = Total number of fatal and serious injury accidents
Share of fatal and serious injury accidents (%) = Number of fatal and serious injury accidents / Number of casualty accidents × 100*3) With regards to the analytical results from the microdata, attention must be paid to the impact that the number of data points hason the accuracy.

Table 1. Number of accidents by type of accident between four-wheel vehicles
and the share of fatal and serious injury accidents [macrodata (2009 - 2018)]
Number of casualty accidents

Number of fatal andserious injury accidents

Share of fatal andserious injury accidents (%)① 20.0

Head-on collision④

95,988② 19,224

Rear-end collision① 1,942,032③ 19,217

1.0

Crossing collision②

640,099① 29,167③ 4.6

22,031

446

2.0

③

123,680④ 8,537② 6.9
2.2

Collision while turning left
Collision between a vehicle turning right /Collision whileoncoming vehicle going straightturning right

38,490859

Collision while passing or overtaking

26,383712

2.7

Collision while passing each other

30,838

1,099

④ 3.6

Other

283,024

5,914

2.1

Other

ITARDA INFORMATION no.136

0.2

100％

Composition ratelSpeciafeature

80％

22.1

0.4

0.1
20.8

0.5

Operating errors

60％
40％

65.7

65.9

11.5

12.7

Age 65 and older（n＝27,298）

Age 64 and younger（n＝96,382）

20％
0％Causes of collision accidents between four-wheel vehicles

Table 2 shows the numbers for collision accidents between four-wheel vehicles turning right and four-wheel vehicles goingstraight by their causes by what factors are at play from the perspective of causes attributable to human factors, factors with theroad environment, or vehicle factors. It also shows the share out of the total number of casualty accidents that these account for.
This reveals that the majority of these were attributable to human factors, with only a small fraction of each attributable to roadenvironment-related factors or vehicle-related factors.
Next, looking at the human factors involved in accidents
Table 2. Number of collision accidents between
between a vehicle turning right and a vehicle going straightfour-wheel vehicles turning right and four-wheelfrom the graph on the front cover (composition rate by humanvehicles going straight by factors attributable to thefactor of the primary party) shows that the most common
primary party and the share of the total number offactor behind collision accidents between a four-wheel vehicle
casualty accidents these account for
turning right and a four-wheel vehicle going straight was a
failure to confirm safety factors that led to a delay in noticing,which accounted for two-thirds of the whole. A common factor
Number of accidents
Share (%) *4
with head-on collisions and rear-end collisions is a failure to
Human factors at play
123,524
99.9
pay attention to what is up ahead, which stands in starkRoad
environment-related
factors
at
play
2,526
2.0
contrast with the fact that a failure to confirm safety factors is
uncommon. In addition, with accidents between a vehicle
Vehicle-related factors at play108
0.1
turning right and a vehicle going straight, a failure to confirm[Macrodata (2009 - 2018)]
safety factors and a failure to pay attention to what is up ahead
combined account for nearly 80% of the total. This reveals that *4) Share by cause (%) = Number of accidents by each cause / 123,680
a delay in noticing oncoming vehicles as a result of these two(total number of casualty accidents out of accidents between afactors serves as the primary cause of such accidents.
vehicle turning right and a vehicle going straight) × 100
ITARDA INFORMATION no.136

Errors in judgment
Delay in noticing(failure to conﬁrm
safety factors)
Delay in noticing(failure to conﬁrm
what is up ahead)Fig. 1. Human factors on the part of the primary party by age group for collision accidents
between a four-wheel vehicle turning right and a four-wheel vehicle going straight[macrodata (2009 - 2018)]

Next, Fig. 2 shows collision accidents between a four-wheel vehicle turning right and a four-wheel vehicle going straight by thelocations where they occurred. Intersections accounted for just under 90% of the total, with more than 70% of these occurring at
signalized intersections.
At intersections, there are numerous other entities that get involved in accidents from collisions while turning right aside fromoncoming vehicles, including crossing pedestrians, bicycles, and other vehicles beyond the right turn. In addition, it is believedthat the fact that cases where there are a large number of lanes at signalized intersections and the large number of entities in andof themselves due to traffic congestion increases the share of accidents that occur there. It will presumably be important toenable drivers to quickly notice dangers from among the many entities found at intersections for the sake of avoiding accidents.
But when it comes to accidents between a vehicle turning right and a vehicle going straight, what are the original causal factorsthat give rise to this delay in noticing oncoming vehicles, such as a failure to confirm safety factors?

2.0%

10.1%

0.3%
Intersection - Signalized[The numbers in circles in Table 1 indicate their rank from the top-ranked entry for each category (excluding “Other”)]

2 turning right and four-wheel vehicles going straight

Other

Intersection - Non-signalized

15.8%
71.8%

Near an intersection
Uninterrupted road section
Other（n＝123,680）

Fig. 2. Locations where collision accidents between four-wheel vehicles
turning right and four-wheel vehicles going straight occurred [macrodata (2009 - 2018)]

Why did a delay in noticing an oncoming vehicle going
3 straight occur on the part of the vehicle turning right?
■ When did the driver notice the oncoming vehicle going straight?

From here on, we will take a look at the main causes behind the drivers' delay in noticing oncoming vehicles going straight byfocusing on accidents caused by the drivers of vehicles turning right involved in accidents between a vehicle turning right and avehicle going straight from the microdata between 2009 and 2018. First, it is the author's intention to begin by ascertaining thepoint where the driver first noticed the other vehicle. When did the driver of the vehicle turning right first notice the oncoming
vehicle going straight and when did they collide with them?
ITARDA INFORMATION no.136lSpeciafeatureAccidents from collisions between four-wheel vehicles turning rightand four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles is effective for avoiding accidents ~ITARDA INFORMATION no.136

Fig. 3 shows a conceptual diagram of the points of travel from when the vehicle turning right entered the intersection up until the
point where it collided with the oncoming vehicle going straight in a step-by-step manner (① - ⑤). These can respectively be
defined as follows: ① Point where the vehicle entered the intersection = Point where the vehicle turning right approached the stop
line just before the intersection. ② Point where the vehicle came to a temporary stop = Point where the vehicle turning right cameto a temporary stop at the intersection. ③ Point where the vehicle began turning right = Point where the driver began the processof turning right, such as by cutting the wheel. ④ Point where the driver noticed the oncoming vehicle going straight = Point where
the driver of the vehicle turning right noticed the oncoming vehicle going straight at the intersection. ⑤ Point where the collisionoccurred = Point where the vehicle turning right and the vehicle going straight collided at the intersection. Based on testimony fromthe parties to the accident, for each accident the distance between each point was inferred from the travel locations recorded on
the diagram of the scene of the accident. With accidents between a vehicle turning right and a vehicle going straight there are twomain travel patterns: ①→②→③→④→⑤ and ①→③→④→⑤, where there is no Point ② where the vehicle temporarily stopped.
Oncoming vehicle
going straight

Oncoming vehicle⑤ Point where thegoing straightcollision occurred①Point where the vehicle
entered the intersection

Fig. 4 reveals that in more than 90% of the cases (27 of the 28 accidents), the distance between the point where the driver noticed
the oncoming vehicle going straight and the point where the collision occurred was shorter than the distance needed to stop. This
indicates that it was theoretically impossible to avoid the collision at the point in time where the driver noticed the oncoming vehicle
going straight. In addition, just shy of 90% of the accidents (25 of the 28 accidents) were distributed within the brake reaction area.
This reveals that these collisions occurred when the driver failed to notice the oncoming vehicle going straight (distance between
the point the driver noticed the other vehicle and the point where the collision occurred = 0m) or when they noticed said vehicle
right before the collision and just after they began to decelerate. So then why were they unable to notice the oncoming vehicle
going straight until right before the collision was imminent?

■ What caused the delay in noticing the oncoming vehicle going straight on the part of the driverof the vehicle turning right?

The specific human factors behind 46 accidents deemed to have been caused by a delay in noticing an oncoming vehicle goingstraight inferred from testimony from the driver of the vehicle turning right as a party to the accident were organized andcategorized into Table 3.
The results indicated that a failure to confirm safety factors due to the three factors of "Preoccupied by the area out beyond theright turn," "Did not realize an oncoming vehicle going straight was approaching," and "The vehicle ahead of the driver turned
right and the driver thought their vehicle could make it as well (following the vehicle ahead of them)" accounted forapproximately 80% of the total (36 out of 46 accidents). We will now take a look at each of these cases.

Distance④ Point where the driver noticed
the oncoming vehicle going straight

Table 3. Specific human factors behind accidents between a vehicle turning right and a vehicle goingstraight deemed to have been caused by a delay in noticing the oncoming vehicle going straightSpeciﬁc human factors

Oncoming vehicle
going straight

Oncoming vehicle
going straight② Point where the vehicle cameto a temporary stop

③ Point where the vehicle
began turning right

Number of accidents

Neglected to pay attention to what was ahead due to being distracted

3

Neglected to pay attention to what was ahead due to being absentminded

2

Insuﬃciently checked to ensure safety because the driver was preoccupied with the area out beyond the right turn

15

Neglected to check to ensure it was safe due to a mistaken impression where the driver did not realize an oncoming
vehicle going straight was approaching

15

Neglected to check to ensure it was safe due to the mistaken impression in which, because the vehicle ahead turned
right, the driver thought their vehicle could make it as well (following the vehicle ahead of them)

6

Other

5
[Microdata on 46 accidents (2009 - 2018)]

Brake reaction distance(approx. 7m)

Braking distance(approx. 7m)

15

Stop

20

25

30

Distance between the point where thedriver noticed the other vehicle - point
where the collision occurred (m)35(Example) Stopping distance required when thevehicle's traveling speed is 30km/h

Distance needed to stop
(approx. 14m in total)

Fig. 4. Actual distance between the point where the driver noticed the oncoming vehicle going straightand the point where the collision occurred and the distance needed to stop based on calculations

120 orgreater

10
Sudden braking

110 orgreater5Brake reaction(0.8 seconds)

100 orgreater0

Driver notices
oncoming vehicle

0
90 or
greater： Casualty accidents (failure to notice)

80 orgreater0

Point where the vehicle
began turning right

2

70 or
greater： Casualty accidents (delay in noticing)

10

4

60 or
greater

20

50 orgreater

Collision avoidance area

40 orgreater

30

Angles needed to conﬁrm it was safe
(lane of the oncoming vehicle
going straight and area out
beyond the right turn)

Lane of the oncoming vehicle
going straight and area out
beyond the right turn
Just the lane of the oncoming
vehicle going straight

6

30 or
greater

Distance needed to stop

20 or
greater

Deceleration area

8

Person s central
ﬁeld of vision (40°)

10 orgreaterBrake reaction
50
Brake reaction distance
area
40

10

[Angles needed to conﬁrm it was safe from the point wherethe vehicle began turning right]

0 or
greater

Speed (km/h)

In the microdata from 2009 - 2018, there were 46 accidents between a vehicle turning right and a vehicle going straight that weredeemed to have been caused by a delay in noticing the oncoming vehicle going straight on the part of the driver of the vehicle
turning right. Of these, there were 28 accidents where the traveling speed at the point where the driver noticed the oncoming
vehicle going straight (④) and the distance between this point and the point where the collision occurred (④→⑤) could beascertained. For these accidents, the vehicle's speed and these distances were plotted on Fig. 4. In addition, a solid black line
was used to indicate the distance needed for a four-wheel vehicle to come to a stop based on calculations on this same graph.
The distance needed to come to a stop was found by totaling the brake reaction distance calculated based on a reaction time*5 of
0.8 seconds (the solid gray line) and the braking distance calculated based on a deceleration from braking of 0.5G.
*5) Time from after the driver notices the oncoming vehicle going straight until they begin decelerating by applying the brake

Number of accidents

Fig. 3. Points of travel from when the vehicle turning right enters the intersection until
the collision occurs (conceptual diagram)● Cases where the driver was preoccupied with the area out beyond the right turn (microdata on 15 accidents)
These are primarily cases in which it was found, based on the testimony of the parties to the accident, that the driver was notlooking at the oncoming vehicle going straight, but was instead looking at the road conditions, vehicles, stores, crossing
pedestrians, whether or not there were bicycles, and so forth in the area out beyond the right turn. Why then did this lead themto neglect to check in one direction?
Fig. 5 shows the results of arranging the angles needed to confirm it was safe in cases where the driver is only looking at thelane of oncoming vehicles going straight from the point where the vehicle began turning right and cases where they werelooking at this lane and the area out beyond the right turn for the locations where the 15 accidents subject to review occurred.
The angles needed to confirm it was safe were determined based on a combination of the width of the crossing road, thecrossing angle, and the point where the vehicle began turning right.

Angles needed to conﬁrm
it was safe
(Just the lane of the oncoming
vehicle going straight)（conceptual diagram）

Angles needed to conﬁrm it was safe (°)
Fig. 5. Angles needed to confirm it was safe from the point where the vehicle began turning right incases where the driver was preoccupied by the area out beyond the right turn[microdata on 15 accidents (2009 - 2018)][microdata on 28 accidents (2009 - 2018)]

ITARDA INFORMATION no.136

ITARDA INFORMATION no.136lSpeciafeatureAccidents from collisions between four-wheel vehicles turning rightand four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles is effective for avoiding accidents ~ITARDA INFORMATION no.136

Fig. 3 shows a conceptual diagram of the points of travel from when the vehicle turning right entered the intersection up until the
point where it collided with the oncoming vehicle going straight in a step-by-step manner (① - ⑤). These can respectively be
defined as follows: ① Point where the vehicle entered the intersection = Point where the vehicle turning right approached the stop
line just before the intersection. ② Point where the vehicle came to a temporary stop = Point where the vehicle turning right cameto a temporary stop at the intersection. ③ Point where the vehicle began turning right = Point where the driver began the processof turning right, such as by cutting the wheel. ④ Point where the driver noticed the oncoming vehicle going straight = Point where
the driver of the vehicle turning right noticed the oncoming vehicle going straight at the intersection. ⑤ Point where the collisionoccurred = Point where the vehicle turning right and the vehicle going straight collided at the intersection. Based on testimony fromthe parties to the accident, for each accident the distance between each point was inferred from the travel locations recorded on
the diagram of the scene of the accident. With accidents between a vehicle turning right and a vehicle going straight there are twomain travel patterns: ①→②→③→④→⑤ and ①→③→④→⑤, where there is no Point ② where the vehicle temporarily stopped.
Oncoming vehicle
going straight

Oncoming vehicle⑤ Point where thegoing straightcollision occurred①Point where the vehicle
entered the intersection

Fig. 4 reveals that in more than 90% of the cases (27 of the 28 accidents), the distance between the point where the driver noticed
the oncoming vehicle going straight and the point where the collision occurred was shorter than the distance needed to stop. This
indicates that it was theoretically impossible to avoid the collision at the point in time where the driver noticed the oncoming vehicle
going straight. In addition, just shy of 90% of the accidents (25 of the 28 accidents) were distributed within the brake reaction area.
This reveals that these collisions occurred when the driver failed to notice the oncoming vehicle going straight (distance between
the point the driver noticed the other vehicle and the point where the collision occurred = 0m) or when they noticed said vehicle
right before the collision and just after they began to decelerate. So then why were they unable to notice the oncoming vehicle
going straight until right before the collision was imminent?

■ What caused the delay in noticing the oncoming vehicle going straight on the part of the driverof the vehicle turning right?

The specific human factors behind 46 accidents deemed to have been caused by a delay in noticing an oncoming vehicle goingstraight inferred from testimony from the driver of the vehicle turning right as a party to the accident were organized andcategorized into Table 3.
The results indicated that a failure to confirm safety factors due to the three factors of "Preoccupied by the area out beyond theright turn," "Did not realize an oncoming vehicle going straight was approaching," and "The vehicle ahead of the driver turned
right and the driver thought their vehicle could make it as well (following the vehicle ahead of them)" accounted forapproximately 80% of the total (36 out of 46 accidents). We will now take a look at each of these cases.

Distance④ Point where the driver noticed
the oncoming vehicle going straight

Table 3. Specific human factors behind accidents between a vehicle turning right and a vehicle goingstraight deemed to have been caused by a delay in noticing the oncoming vehicle going straightSpeciﬁc human factors

Oncoming vehicle
going straight

Oncoming vehicle
going straight② Point where the vehicle cameto a temporary stop

③ Point where the vehicle
began turning right

Number of accidents

Neglected to pay attention to what was ahead due to being distracted

3

Neglected to pay attention to what was ahead due to being absentminded

2

Insuﬃciently checked to ensure safety because the driver was preoccupied with the area out beyond the right turn

15

Neglected to check to ensure it was safe due to a mistaken impression where the driver did not realize an oncoming
vehicle going straight was approaching

15

Neglected to check to ensure it was safe due to the mistaken impression in which, because the vehicle ahead turned
right, the driver thought their vehicle could make it as well (following the vehicle ahead of them)

6

Other

5
[Microdata on 46 accidents (2009 - 2018)]

Brake reaction distance(approx. 7m)

Braking distance(approx. 7m)

15

Stop

20

25

30

Distance between the point where thedriver noticed the other vehicle - point
where the collision occurred (m)35(Example) Stopping distance required when thevehicle's traveling speed is 30km/h

Distance needed to stop
(approx. 14m in total)

Fig. 4. Actual distance between the point where the driver noticed the oncoming vehicle going straightand the point where the collision occurred and the distance needed to stop based on calculations

120 orgreater

10
Sudden braking

110 orgreater5Brake reaction(0.8 seconds)

100 orgreater0

Driver notices
oncoming vehicle

0
90 or
greater： Casualty accidents (failure to notice)

80 orgreater0

Point where the vehicle
began turning right

2

70 or
greater： Casualty accidents (delay in noticing)

10

4

60 or
greater

20

50 orgreater

Collision avoidance area

40 orgreater

30

Angles needed to conﬁrm it was safe
(lane of the oncoming vehicle
going straight and area out
beyond the right turn)

Lane of the oncoming vehicle
going straight and area out
beyond the right turn
Just the lane of the oncoming
vehicle going straight

6

30 or
greater

Distance needed to stop

20 or
greater

Deceleration area

8

Person s central
ﬁeld of vision (40°)

10 orgreaterBrake reaction
50
Brake reaction distance
area
40

10

[Angles needed to conﬁrm it was safe from the point wherethe vehicle began turning right]

0 or
greater

Speed (km/h)

In the microdata from 2009 - 2018, there were 46 accidents between a vehicle turning right and a vehicle going straight that weredeemed to have been caused by a delay in noticing the oncoming vehicle going straight on the part of the driver of the vehicle
turning right. Of these, there were 28 accidents where the traveling speed at the point where the driver noticed the oncoming
vehicle going straight (④) and the distance between this point and the point where the collision occurred (④→⑤) could beascertained. For these accidents, the vehicle's speed and these distances were plotted on Fig. 4. In addition, a solid black line
was used to indicate the distance needed for a four-wheel vehicle to come to a stop based on calculations on this same graph.
The distance needed to come to a stop was found by totaling the brake reaction distance calculated based on a reaction time*5 of
0.8 seconds (the solid gray line) and the braking distance calculated based on a deceleration from braking of 0.5G.
*5) Time from after the driver notices the oncoming vehicle going straight until they begin decelerating by applying the brake

Number of accidents

Fig. 3. Points of travel from when the vehicle turning right enters the intersection until
the collision occurs (conceptual diagram)● Cases where the driver was preoccupied with the area out beyond the right turn (microdata on 15 accidents)
These are primarily cases in which it was found, based on the testimony of the parties to the accident, that the driver was notlooking at the oncoming vehicle going straight, but was instead looking at the road conditions, vehicles, stores, crossing
pedestrians, whether or not there were bicycles, and so forth in the area out beyond the right turn. Why then did this lead themto neglect to check in one direction?
Fig. 5 shows the results of arranging the angles needed to confirm it was safe in cases where the driver is only looking at thelane of oncoming vehicles going straight from the point where the vehicle began turning right and cases where they werelooking at this lane and the area out beyond the right turn for the locations where the 15 accidents subject to review occurred.
The angles needed to confirm it was safe were determined based on a combination of the width of the crossing road, thecrossing angle, and the point where the vehicle began turning right.

Angles needed to conﬁrm
it was safe
(Just the lane of the oncoming
vehicle going straight)（conceptual diagram）

Angles needed to conﬁrm it was safe (°)
Fig. 5. Angles needed to confirm it was safe from the point where the vehicle began turning right incases where the driver was preoccupied by the area out beyond the right turn[microdata on 15 accidents (2009 - 2018)][microdata on 28 accidents (2009 - 2018)]

ITARDA INFORMATION no.136

ITARDA INFORMATION no.136

Accidents from collisions between four-wheel vehicles turning rightand four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles is effective for avoiding accidents ~ITARDA INFORMATION no.136

A person's central field of vision is said to be about 40° (20° in either direction). In cases where a driver is only looking at the laneof oncoming vehicles going straight, based on Fig. 5 we can see that they can only perceive things visually in roughly one
direction, yet when they view both the aforementioned lane and the area out beyond the right turn this encompasses every angle,
representing an area that is two to three times greater than their central field of vision. In other words, compared to a situation inwhich they are only looking at the lane of oncoming vehicles going straight, such as when they are going straight ahead, thisincreases the complexity in the sense that now they have to check to confirm that it is safe two to three times as frequently, which
presumably could potentially lead to a failure to confirm safety factors with collisions while turning right.
● Cases where the driver did not realize an oncoming vehicle going straight was approaching (microdata on 15 accidents)
These are primarily cases in which it was found, based on the testimony of the parties to the accident, that an oncoming vehicle
turning right obstructed the driver's field of vision and they failed to realize that an oncoming vehicle going straight wasapproaching, or there was a situation in which one or two oncoming vehicles in the lane closest to the driver going straight madeit through the intersection but they failed to realize another vehicle going straight was approaching from another lane further awayfrom them.
Fig. 6 shows a breakdown of the 15 accidents subject to review in terms of the share of accidents that occurred by whether or notthere was a blind spot and the number of lanes of oncoming traffic (including right-turn lanes). Accidents that were impacted byoncoming vehicles turning right, oncoming vehicles going straight that were stopped in traffic congestion, and so forth accounted
for two-thirds of all of these cases. In addition, cases where there were a larger number of lanes of oncoming traffic at three orfour accounted for just shy of 80% of the total nursing of cases.
The presence of blind spots and a greater number of oncoming lanes of traffic mean that these are inherently locations andspaces where confirmation must be made. Yet despite this, it is presumably conceivable that these drivers neglected to check to
confirm it was safe out of the mistaken impression that there were not any oncoming vehicles going straight.

5 accidents

5 accidents

Oncoming stopped vehicle
going straight, etc.

2 accidents

5 accidents

No aﬀected vehicles

3 lanes2 lanes2 accidents

1 lane(Whether or not there
was a blind spot)(By number of lanesof oncoming traﬃc)

67％

79％

6 accidents

5 accidents

4 lanesFig. 6. Share of accidents between a vehicle turning right and a vehicle going straight by whether or
not there was a blind spot / number of lanes in cases where the driver did not realize an oncoming
vehicle going straight was approaching [microdata on 15 accidents (2009 - 2018)]● Cases where the vehicle ahead turned right and the driver thought their vehicle could make it as well (following the vehicle
ahead of them) [microdata on 6 accidents]
These are primarily cases in which it was found, based on the testimony of the parties to the accident, that since the previous
vehicle turned right the driver thought that no oncoming vehicles were approaching, or thought it was safe since the vehicle
ahead of them made a right turn. These accidents seem to have occurred because the driver was under the mistaken impressionthat since the previous vehicle turned right, thiseffectively served as a priori confirmation that it was
Proceeded forward
Temporary stop
safe.
Unclearwithout stopping→Starting up
Fig. 7 shows a breakdown of driving behavior at
100％
intersections. The share of cases where the driver0 accidents
proceeded ahead without stopping accounted for
1 accident
80％
more than 80% (five out of six accidents) of cases
where the driver followed the vehicle ahead of them,
1 accident
60％
which represents a significant difference in that this21 accidents
is just over 50% for all 46 accidents on the whole (2440％
out of 46 accidents). It is believed that a sentiment ofwanting to rush through the right turn without
attempting to act prudently, such as by coming to a20％
temporar y stop, could potentially give rise to
5 accidents
24 accidents
mistaken impressions like this on the part of drivers.
0％Composition rate

It has become apparent that having the driver preoccupied with the area out beyond the right turn, the presence of blind spots, alarge number of lanes, and mistaken impressions caused by the movement of the vehicle up ahead have led drivers to neglect tocheck for oncoming vehicles going straight and thus to a delay in noticing other vehicles. On such occasions, it is important toadopt an attitude of placing the highest priority on checking for oncoming vehicles going straight and not rushing into making aright turn. Specifically, the driver must repeatedly go back and forth between checking the lane of oncoming vehicles goingstraight, the area beyond the right turn, and then the lane of oncoming vehicles going straight again. They must then thoroughly
ensure that they proceed into the intersection without rushing the right turn, such as by coming to a temporary stop or moving atvery low speeds.
In this sense, it will be necessary to provide support for making right turns, as such actions place a significant burden on thedriver, from the perspective of the road environment and vehicle technology. From a road environment perspective, the hope isthat in the future progress will continue to be made on alleviating the burden placed on drivers who have to check the lane ofoncoming vehicles going straight. This can be done by shifting the right turn lane closer to the oncoming vehicle lane to make iteasier to see, and increasing the number of traffic signals equipped with right turn-only signs (right arrows) primarily forintersections with a large number of lanes. Furthermore, from a vehicle technology perspective the hope is that efforts such asproviding drivers with advance warning of the approach of oncoming vehicles going straight can lead to them properly noticing
these other vehicles, determining the danger posed, and acting to avoid it. This can be achieved through cutting-edge safety
technologies such as warnings through detection by automatic sensors, damage mitigation brakes suited to handling collision
accidents while turning right, and signals between vehicles and between the road and vehicles.
For the 28 accidents from Fig. 4, back-of-the-envelope estimates of the number of accidents that could have potentially been
stopped before the collision*6 were made for different cases, with the results shown in Fig. 8 and Fig. 9, respectively. These cases
are: 1) An alarm notifies the driver of the oncoming vehicle going straight at the point where the vehicle began turning right (Fig. 3③), and the driver applies the brakes (or damage mitigation brakes activate). 2) An advance notification *7 from signals between
vehicles or between the road and the vehicle notifies the driver at the stage right before they begin making the right turn (point
where the vehicle entered the intersection (Fig. 3 ①) or the point where the vehicle came to a temporary stop (Fig. 3 ②)) and thedriver applies the brakes. The reaction time (0.8 seconds), deceleration (0.5G), and traveling speed when the driver noticed theoncoming vehicle going straight were assumed to be the same as in Fig. 4.

83％

Following the vehicle
ahead（6 accidents）

52％

Overall（46 accidents）

Fig. 7. Comparison of driving behavior at an intersection

Speed (km/h)

Oncoming vehicle
turning rightCountermeasures against the delay in noticing oncoming

4 vehicles going straight and their expected results

50
40
30

Brake reaction
area

Brake reaction
distance

Deceleration area

Distance needed to stop

Collision avoidance area

20
10
0

： Casualty accidents
0

5

10

15

20

25

30

35

Distance from the point where the vehicle began turning right to right before the collision (m)Fig. 8. Whether or not a collision occurred in cases where the driver noticed the other vehicle
and braked at the point where the vehicle began turning right [microdata on 28 accidents (2009 - 2018)]
Brake reaction
distance

50

Speed (km/h)lSpeciafeature40
30

Brake reaction
area

Deceleration area

Distance needed to stop

Collision avoidance area

20
10
0

： Casualty accidents
0

5

10

15

20

25

30

35

Distance from the point where the vehicle entered the intersection / point where the vehicle came toa temporary stop to right before the collision (m)Fig. 9. Whether or not a collision occurred in cases where the driver noticed the other vehicle andbraked at the stage prior to starting to turn right [microdata on 28 accidents (2009 - 2018)]*6) The point right before where the vehicle turning right entered the line of motion of the oncoming vehicle going straight*7) Assistance systems to prevent collisions while turning right through the use of signals considered in sources like the Plan for
Promotion of the Development of Advanced Safety Vehicles (ASV) by the Ministry of Land, Infrastructure, Transport and Tourism

Based on the results of these back-of-the-envelope estimates, in the case of 1) collisions could have been avoided 50% of thetime (14 out of 28 accidents) (Fig. 8). In the case of 2), collisions could have been avoided in more than 70% of the time (20 out of
28 accidents) (Fig. 9). As the above indicates, combining improvements in driver awareness and behavior with assistance fromthe road environment and vehicle technology could presumably give rise to greater effects in terms of reducing accidents.

[microdata on 46 accidents (2009 - 2018)]

ITARDA INFORMATION no.136

ITARDA INFORMATION no.136

Accidents from collisions between four-wheel vehicles turning rightand four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles is effective for avoiding accidents ~ITARDA INFORMATION no.136

A person's central field of vision is said to be about 40° (20° in either direction). In cases where a driver is only looking at the laneof oncoming vehicles going straight, based on Fig. 5 we can see that they can only perceive things visually in roughly one
direction, yet when they view both the aforementioned lane and the area out beyond the right turn this encompasses every angle,
representing an area that is two to three times greater than their central field of vision. In other words, compared to a situation inwhich they are only looking at the lane of oncoming vehicles going straight, such as when they are going straight ahead, thisincreases the complexity in the sense that now they have to check to confirm that it is safe two to three times as frequently, which
presumably could potentially lead to a failure to confirm safety factors with collisions while turning right.
● Cases where the driver did not realize an oncoming vehicle going straight was approaching (microdata on 15 accidents)
These are primarily cases in which it was found, based on the testimony of the parties to the accident, that an oncoming vehicle
turning right obstructed the driver's field of vision and they failed to realize that an oncoming vehicle going straight wasapproaching, or there was a situation in which one or two oncoming vehicles in the lane closest to the driver going straight madeit through the intersection but they failed to realize another vehicle going straight was approaching from another lane further awayfrom them.
Fig. 6 shows a breakdown of the 15 accidents subject to review in terms of the share of accidents that occurred by whether or notthere was a blind spot and the number of lanes of oncoming traffic (including right-turn lanes). Accidents that were impacted byoncoming vehicles turning right, oncoming vehicles going straight that were stopped in traffic congestion, and so forth accounted
for two-thirds of all of these cases. In addition, cases where there were a larger number of lanes of oncoming traffic at three orfour accounted for just shy of 80% of the total nursing of cases.
The presence of blind spots and a greater number of oncoming lanes of traffic mean that these are inherently locations andspaces where confirmation must be made. Yet despite this, it is presumably conceivable that these drivers neglected to check to
confirm it was safe out of the mistaken impression that there were not any oncoming vehicles going straight.

5 accidents

5 accidents

Oncoming stopped vehicle
going straight, etc.

2 accidents

5 accidents

No aﬀected vehicles

3 lanes2 lanes2 accidents

1 lane(Whether or not there
was a blind spot)(By number of lanesof oncoming traﬃc)

67％

79％

6 accidents

5 accidents

4 lanesFig. 6. Share of accidents between a vehicle turning right and a vehicle going straight by whether or
not there was a blind spot / number of lanes in cases where the driver did not realize an oncoming
vehicle going straight was approaching [microdata on 15 accidents (2009 - 2018)]● Cases where the vehicle ahead turned right and the driver thought their vehicle could make it as well (following the vehicle
ahead of them) [microdata on 6 accidents]
These are primarily cases in which it was found, based on the testimony of the parties to the accident, that since the previous
vehicle turned right the driver thought that no oncoming vehicles were approaching, or thought it was safe since the vehicle
ahead of them made a right turn. These accidents seem to have occurred because the driver was under the mistaken impressionthat since the previous vehicle turned right, thiseffectively served as a priori confirmation that it was
Proceeded forward
Temporary stop
safe.
Unclearwithout stopping→Starting up
Fig. 7 shows a breakdown of driving behavior at
100％
intersections. The share of cases where the driver0 accidents
proceeded ahead without stopping accounted for
1 accident
80％
more than 80% (five out of six accidents) of cases
where the driver followed the vehicle ahead of them,
1 accident
60％
which represents a significant difference in that this21 accidents
is just over 50% for all 46 accidents on the whole (2440％
out of 46 accidents). It is believed that a sentiment ofwanting to rush through the right turn without
attempting to act prudently, such as by coming to a20％
temporar y stop, could potentially give rise to
5 accidents
24 accidents
mistaken impressions like this on the part of drivers.
0％Composition rate

It has become apparent that having the driver preoccupied with the area out beyond the right turn, the presence of blind spots, alarge number of lanes, and mistaken impressions caused by the movement of the vehicle up ahead have led drivers to neglect tocheck for oncoming vehicles going straight and thus to a delay in noticing other vehicles. On such occasions, it is important toadopt an attitude of placing the highest priority on checking for oncoming vehicles going straight and not rushing into making aright turn. Specifically, the driver must repeatedly go back and forth between checking the lane of oncoming vehicles goingstraight, the area beyond the right turn, and then the lane of oncoming vehicles going straight again. They must then thoroughly
ensure that they proceed into the intersection without rushing the right turn, such as by coming to a temporary stop or moving atvery low speeds.
In this sense, it will be necessary to provide support for making right turns, as such actions place a significant burden on thedriver, from the perspective of the road environment and vehicle technology. From a road environment perspective, the hope isthat in the future progress will continue to be made on alleviating the burden placed on drivers who have to check the lane ofoncoming vehicles going straight. This can be done by shifting the right turn lane closer to the oncoming vehicle lane to make iteasier to see, and increasing the number of traffic signals equipped with right turn-only signs (right arrows) primarily forintersections with a large number of lanes. Furthermore, from a vehicle technology perspective the hope is that efforts such asproviding drivers with advance warning of the approach of oncoming vehicles going straight can lead to them properly noticing
these other vehicles, determining the danger posed, and acting to avoid it. This can be achieved through cutting-edge safety
technologies such as warnings through detection by automatic sensors, damage mitigation brakes suited to handling collision
accidents while turning right, and signals between vehicles and between the road and vehicles.
For the 28 accidents from Fig. 4, back-of-the-envelope estimates of the number of accidents that could have potentially been
stopped before the collision*6 were made for different cases, with the results shown in Fig. 8 and Fig. 9, respectively. These cases
are: 1) An alarm notifies the driver of the oncoming vehicle going straight at the point where the vehicle began turning right (Fig. 3③), and the driver applies the brakes (or damage mitigation brakes activate). 2) An advance notification *7 from signals between
vehicles or between the road and the vehicle notifies the driver at the stage right before they begin making the right turn (point
where the vehicle entered the intersection (Fig. 3 ①) or the point where the vehicle came to a temporary stop (Fig. 3 ②)) and thedriver applies the brakes. The reaction time (0.8 seconds), deceleration (0.5G), and traveling speed when the driver noticed theoncoming vehicle going straight were assumed to be the same as in Fig. 4.

83％

Following the vehicle
ahead（6 accidents）

52％

Overall（46 accidents）

Fig. 7. Comparison of driving behavior at an intersection

Speed (km/h)

Oncoming vehicle
turning rightCountermeasures against the delay in noticing oncoming

4 vehicles going straight and their expected results

50
40
30

Brake reaction
area

Brake reaction
distance

Deceleration area

Distance needed to stop

Collision avoidance area

20
10
0

： Casualty accidents
0

5

10

15

20

25

30

35

Distance from the point where the vehicle began turning right to right before the collision (m)Fig. 8. Whether or not a collision occurred in cases where the driver noticed the other vehicle
and braked at the point where the vehicle began turning right [microdata on 28 accidents (2009 - 2018)]
Brake reaction
distance

50

Speed (km/h)lSpeciafeature40
30

Brake reaction
area

Deceleration area

Distance needed to stop

Collision avoidance area

20
10
0

： Casualty accidents
0

5

10

15

20

25

30

35

Distance from the point where the vehicle entered the intersection / point where the vehicle came toa temporary stop to right before the collision (m)Fig. 9. Whether or not a collision occurred in cases where the driver noticed the other vehicle andbraked at the stage prior to starting to turn right [microdata on 28 accidents (2009 - 2018)]*6) The point right before where the vehicle turning right entered the line of motion of the oncoming vehicle going straight*7) Assistance systems to prevent collisions while turning right through the use of signals considered in sources like the Plan for
Promotion of the Development of Advanced Safety Vehicles (ASV) by the Ministry of Land, Infrastructure, Transport and Tourism

Based on the results of these back-of-the-envelope estimates, in the case of 1) collisions could have been avoided 50% of thetime (14 out of 28 accidents) (Fig. 8). In the case of 2), collisions could have been avoided in more than 70% of the time (20 out of
28 accidents) (Fig. 9). As the above indicates, combining improvements in driver awareness and behavior with assistance fromthe road environment and vehicle technology could presumably give rise to greater effects in terms of reducing accidents.

[microdata on 46 accidents (2009 - 2018)]

ITARDA INFORMATION no.136

ITARDA INFORMATION no.136

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 https://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・東京交通事故調査事務所〒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.136

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10

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イタルダインフォメーションに関するお問い合せ先 渉外事業課

ITARDA INFORMATION
交通事故分析レポート No.136lSpecia Accidents from collisions between four-wheel vehicles
feature turning right and four-wheel vehicles going straight~ Preventing a delay in noticing other vehicles
is eﬀective for avoiding accidents ~Roughly 80% of such accidents occur due to a delay in noticing the oncoming vehicle
100％

Composition rate

No.136

公益財団法人 交通事故総合分析センター
令和2年 月 〒101 0064 東 京 都 千 代 田 区 神 田 猿 楽 町 ２ ７ ８(Masanori Taniguchi)

ITARDA INFORMATIONThis issue took a look at why accidents between a vehicle turning right and a vehicle going straightoccur and the sorts of countermeasures that are effective for combating them. The majority of thesetypes of accidents occur due to a delay in noticing the oncoming vehicle going straight by the driver ofthe vehicle turning right. The three factors below serve as the main causes giving rise to this delay innoticing the other vehicle, and it is important that we once again recognize the difficulty inherent inmaking right turns.
・ The increased complexity of making confirmation due to the wide angle needed to confirm it wassafe at the intersection made it difficult to sufficiently confirm that it was safe・ The presence of blind spots and a large number of lanes engendered a mistaken impression in thedriver that there were no oncoming vehicles going straight approaching and they neglected toconfirm that it was safe
・ A sentiment of rushing through the right turn so as to follow after the vehicle before themengendered in the driver the mistaken impression that the previous vehicle had already provided apriori confirmation that it was safe and they neglected to confirm that it was safe
Countermeasures include:
・ Improve the awareness / behavior of the driver of the vehicle turning right: They must repeatedly goback and forth between checking the lane of oncoming vehicles going straight, the area beyond theright turn, and then the lane of oncoming vehicles going straight again. They must then thoroughly
ensure that they proceed into the intersection without rushing the right turn, such as by coming to atemporary stop or moving at very low speeds.
・ Assistance from the road environment: Shift right-turn lanes closer to the oncoming vehicle lane
and adopt traffic signals equipped with right turn-only signs (right arrows) primarily for intersections
with a large number of lanes.
・ Assistance from vehicle technology: Practically implement and adopt cutting-edge safety
technologies such as warnings via sensor detection, damage mitigation brakes suited to handlingcollision accidents while turning right, and advance warnings through the use of signals between
vehicles and the between road and vehicles.
Combining and disseminating the countermeasures listed above in an effective manner can be
expected to prevent a delay in noticing other vehicles on the part of drivers, and could help to further
reduce accidents between vehicles turning right and vehicles going straight.

交通事故分析レポート

5 Conclusion

イタルダ インフォメーション

80％

21.1

0.1
0.5

60％
40％

1.2

12.3
11.2

12.4

0.1

24.7

Other
Errors in judgment
Delay in noticing(failure to conﬁrm
safety factors)
Delay in noticing(failure to conﬁrm
what is up ahead)

53.3

56.0

Head-on collision（n＝95,988）

Rear-end collision（n＝1,942,032）

12.4
Collision between a vehicle
turning right and a vehicle
going straight*1

Operating errors

6.8

65.9

20％
0％

22.1

（n＝123,680）

Human factors on the part of the primary party
for vehicle-vehicle accidents between four-wheel vehicles[Road Traﬃc Accident Statistics (2009 - 2018)]*1. Failure to pay attention to what is up ahead includes failing to notice due to being distracted or absentminded, while failure to conﬁrm safety factors includes
failure to notice due to not checking to ensure safety or failure to notice due to insuﬃciently checking to ensure safety. Errors in judgment refer to human factors
such as misjudging the distance to or speed of the other vehicle, or a driver failing to pay attention due to the thinking that the other vehicle would yield to them.

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Causes of collision accidents between four-wheel vehicles turning right2 and four-wheel vehicles going straight

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did a delay in noticing an oncoming vehicle going straight occur
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going straight and their expected results

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