While the number of fatal accidents between four-wheel vehicles and bicycles continues to fall in andof itself, the rate of rear-end collision accidents of the fatal accidents that occur on roadways has
been trending upwards year by year. For this reason, countermeasures against rear-end collisions
between four-wheel vehicles and bicycles are growing more important with each passing year. The
regulations in the Road Traffic Act state that bicycles are to travel on the left side of roadways as a
general rule, and so people frequently encounter bicycles being ridden to the left of roadways whendriving automobiles. In order to enable bicycles to travel safely along roadways, we must respond toillegally-parked four-wheel vehicles that pose an obstacle to them. Furthermore, over the medium tolong-term we should ideally also improve the traffic environment for bicycles, including bicycle lanes
and other measures.

ITARDA INFORMATIONThis issue mainly looked at rear-end collision accidents which, out of all of the types of accidents
between four-wheel vehicles and bicycles, tend to lead to the most fatal accidents. Rear-end collision
accidents often occur when the driver of the four-wheel vehicle fails to notice a bicycle, and therefore
this is an accident type that should be handled from the four-wheel vehicle side. Both of the two caseexamples of accidents introduced occurred at night. In the first case, the driver was delayed in
detecting the bicycle because he was preoccupied by the traffic signal up ahead. In the second case,the accident occurred because even though the driver was aware of the bicycle, he failed to respondwhen the bicycle’s path changed. Both of these accident case examples occurred due to a lack ofattention being paid to a bicycle traveling in front of the driver.

交通事故分析レポート

6 Conclusion

TEL 03-5577-3973

FAX 03-5577-3980

公益財団法人 交通事故総合分析センター●ウェブサイト http://www.itarda.or.jp/ ●Eメール koho@itarda.or.jp●フェイスブック https://www.facebook.com/itarda.or
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TEL 03-5577-3977(代表) FAX 03-5577-3980

ITARDA INFORMATION no.125

つくば 交通事故調査事務所

2

住 友 水 道 橋 ビル８ 階

渉外事業課

30

〒101 0064 東 京 都 千 代 田 区 神 田 猿 楽 町 ２ ７ ８イタルダインフォメーションに関するお問い合せ先

交通事故分析レポート No.125
Rear-end collision accidents between
four-wheel vehicles and bicycleslSpeciafeature~ Be careful not to overlook cyclists at nighton the left-hand side of the roadway! ~Number of fatal accidents per 1,000 casualty accidents
Rate of fatal accidents by type of accident between four-wheel vehicles
and bicycles that occurred on roadways*1(Cumulative total from 2012 to 2016)0.0

公益財団法人 交通事故総合分析センター(Akira Yamaguchi)

ITARDA INFORMATION

No.125

Seen from the perspective of four-wheel vehicles, bicycles are vulnerable road users. When driving
four-wheel vehicles, drivers must work to ensure that they drive safely when they detect bicycles
traveling along. Such efforts include paying attention to the bicycle’s movements and, when passingor overtaking them, maintaining as much distance between the bicycle as possible and reducing their
speed to one that is appropriate considering this distance when overtaking them.
On the other side, when it comes to measures to prevent accidents from the bicycle’s side, bicycles
are treated as a type of vehicle and granted the right to travel on roadways. In other words, cyclists
must abide by traffic signals and instructions to stop, as well as travel by obeying other traffic signs
and traffic rules. On top of this, to effectively respond to the rear-end collision accidents covered inthis issue, an approach that is considered to be effective even at night, when visibility is poor, is for
cyclists to equip themselves with equipment that emits light even without having the headlights fromfour-wheel vehicles shined on them. Examples of this include using reflective materials or installing
LED tail lights in order to alert drivers to their presence.

イタルダ インフォメーション

10.0

20.0

30.0

40.0

50.0

Rear-end
collisions
Head-oncollisions
Angle
collisions

60.0

70.0

60 accidents
9 accidents
7 accidents

Collisions
while passing/overtaking

4 accidents

Collisions
when turning
left / right1 accident*1. Rate of fatal accidents: Number of fatal accidents per 1,000 casualty accidents

1 Introduction・
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2 Locations where accidents between four-wheel vehicles and bicycles occur・・・・P3
Rear-end collision accidents accounted for most of the fatal accidents,
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with most of these occurring at night
4 Why is the rate of fatal accidents from rear-end collision accidents so high? ・・・P5
5 Introduction to case examples of accidents ・
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SpeciafeatureRear-end collision accidents between four-wheel vehicles and bicycles~ Be careful not to overlook cyclists at night on the left-hand side of the roadway! ~ITARDA INFORMATION no.125

Locations where accidents between

1 Introduction

2 four-wheel vehicles and bicycles occur

In traffic accidents, the involved parties are divided up into the primary party and the secondary party depending on
the relative degree of their culpability. The number of accidents that occurred in 2016 in which a passenger car (notincluding mini-cars) or a truck (hereafter referred to as “four-wheel vehicles”) was involved as the primary party andwhere the secondary party suffered injuries or death came to 427,111. Of these, 69,631 were accidents in which
the secondary party was a cyclist and suffered injuries or death, 258 of which were fatal accidents.
Fig. 1 shows trends since 1997 in the number of accidents in which the primary party was driving a four-wheel
vehicle and the secondary party who was a cyclist suffered injuries or death. It reveals that casualty accidents rosemoderately between 1997 and 2004, peaked in 2004, and then began trending downwards thereafter. As for fatal
accidents, these have been on a mostly downward trajectory since 1997.
A number of factors can be offered as reasons for this decline in the number of accidents between four-wheel
vehicles and bicycles, such as the revisions to the Road Traffic Act with respect to bicycle use, improvements to thetraffic environment for bicycles, and improvements to the safety performance of vehicles. While these sorts ofoutcomes persist, what sorts of issues must we focus on in order to continue decreasing the number of accidents
between four-wheel vehicles and bicycles in the future? In order to find hints to answering this question, this issueof ITARDA Information No. 125 will take a look at the characteristics of traffic accidents between four-wheel
vehicles and bicycles.

In what sorts of locations do accidents between four-wheel vehicles and bicycles occur? The number of accidents
hereafter will focus on accidents in which the primary party was driving a four-wheel vehicle and the secondary party
was a cyclist and the cyclist either died or was injured. Fig. 2 shows the composition rate by road configurations at
locations where casualty accidents between four-wheel vehicles and bicycles occurred in 2016. Fig. 3 shows thecomposition rate for fatal accidents between the same. Since the number of fatal accidents in Fig. 3 is lower than thenumber of casualty accidents, the cumulative total for the five years from 2012 to 2016 was used.
Intersections constitute the road configuration where the greatest number of accidents between four-wheel vehicles
and bicycles occurred for both casualty accidents and fatal accidents, with these accounting for more than half inboth cases. A higher rate of fatal accidents occurred at non-intersections versus casualty accidents.

1％

23％

6％

11％

32％

69％

800

56％

Fatal accidents (right scale)

150

600

100

400

Casualty accidents (left scale)

50

200

97

98

99

00

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

19

19

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

0
19

0

Number of fatal accidents (accidents)

Number of casualty accidents (1,000 accidents)

200

2％

n＝69,631 accidents

n＝1,585 accidents

Non-intersections

Intersections

Non-intersections

Intersections

Near intersections

Other

Near intersections

Other

Fig. 2. Composition rate by road configurations
for casualty accidents (2016)

Fig. 3. Composition rate by road configurations
for fatal accidents (2012 – 2016)

Let’s look at accidents that occurred at non-intersections in a bit more detail. Figs. 4 and 5 shows the composition
by collision sites for casualty accidents and fatal accidents between four-wheel vehicles and bicycles that occurredat non-intersections. Roadways accounted for more than half of the collision sites at which casualty accidents
occurred at 57%, with sidewalks accounting for 38%. Conversely, an even higher rate of fatal accidents occurredon roadways, with 95% of fatal accidents taking place on roadways.

5％

5％

38％

57％

95％

Years accidents occurredFig. 1. Trends in the number of accidents between four-wheel vehicles and bicycles

n＝16,079 accidents
Roadways

Sidewalks

Other

Fig. 4. Composition rate by collision sites
for casualty accidents at non-intersections (2016)
ITARDA INFORMATION no.125

n＝512 accidents
Roadways

Sidewalks

Other

Fig. 5. Composition rate by collision sites
for fatal accidents at non-intersections (2012 – 2016)
ITARDA INFORMATION no.125lSpeciafeatureRear-end collision accidents between four-wheel vehicles and bicycles~ Be careful not to overlook cyclists at night on the left-hand side of the roadway! ~ITARDA INFORMATION no.125

Locations where accidents between

1 Introduction

2 four-wheel vehicles and bicycles occur

In traffic accidents, the involved parties are divided up into the primary party and the secondary party depending on
the relative degree of their culpability. The number of accidents that occurred in 2016 in which a passenger car (notincluding mini-cars) or a truck (hereafter referred to as “four-wheel vehicles”) was involved as the primary party andwhere the secondary party suffered injuries or death came to 427,111. Of these, 69,631 were accidents in which
the secondary party was a cyclist and suffered injuries or death, 258 of which were fatal accidents.
Fig. 1 shows trends since 1997 in the number of accidents in which the primary party was driving a four-wheel
vehicle and the secondary party who was a cyclist suffered injuries or death. It reveals that casualty accidents rosemoderately between 1997 and 2004, peaked in 2004, and then began trending downwards thereafter. As for fatal
accidents, these have been on a mostly downward trajectory since 1997.
A number of factors can be offered as reasons for this decline in the number of accidents between four-wheel
vehicles and bicycles, such as the revisions to the Road Traffic Act with respect to bicycle use, improvements to thetraffic environment for bicycles, and improvements to the safety performance of vehicles. While these sorts ofoutcomes persist, what sorts of issues must we focus on in order to continue decreasing the number of accidents
between four-wheel vehicles and bicycles in the future? In order to find hints to answering this question, this issueof ITARDA Information No. 125 will take a look at the characteristics of traffic accidents between four-wheel
vehicles and bicycles.

In what sorts of locations do accidents between four-wheel vehicles and bicycles occur? The number of accidents
hereafter will focus on accidents in which the primary party was driving a four-wheel vehicle and the secondary party
was a cyclist and the cyclist either died or was injured. Fig. 2 shows the composition rate by road configurations at
locations where casualty accidents between four-wheel vehicles and bicycles occurred in 2016. Fig. 3 shows thecomposition rate for fatal accidents between the same. Since the number of fatal accidents in Fig. 3 is lower than thenumber of casualty accidents, the cumulative total for the five years from 2012 to 2016 was used.
Intersections constitute the road configuration where the greatest number of accidents between four-wheel vehicles
and bicycles occurred for both casualty accidents and fatal accidents, with these accounting for more than half inboth cases. A higher rate of fatal accidents occurred at non-intersections versus casualty accidents.

1％

23％

6％

11％

32％

69％

800

56％

Fatal accidents (right scale)

150

600

100

400

Casualty accidents (left scale)

50

200

97

98

99

00

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

19

19

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

0
19

0

Number of fatal accidents (accidents)

Number of casualty accidents (1,000 accidents)

200

2％

n＝69,631 accidents

n＝1,585 accidents

Non-intersections

Intersections

Non-intersections

Intersections

Near intersections

Other

Near intersections

Other

Fig. 2. Composition rate by road configurations
for casualty accidents (2016)

Fig. 3. Composition rate by road configurations
for fatal accidents (2012 – 2016)

Let’s look at accidents that occurred at non-intersections in a bit more detail. Figs. 4 and 5 shows the composition
by collision sites for casualty accidents and fatal accidents between four-wheel vehicles and bicycles that occurredat non-intersections. Roadways accounted for more than half of the collision sites at which casualty accidents
occurred at 57%, with sidewalks accounting for 38%. Conversely, an even higher rate of fatal accidents occurredon roadways, with 95% of fatal accidents taking place on roadways.

5％

5％

38％

57％

95％

Years accidents occurredFig. 1. Trends in the number of accidents between four-wheel vehicles and bicycles

n＝16,079 accidents
Roadways

Sidewalks

Other

Fig. 4. Composition rate by collision sites
for casualty accidents at non-intersections (2016)
ITARDA INFORMATION no.125

n＝512 accidents
Roadways

Sidewalks

Other

Fig. 5. Composition rate by collision sites
for fatal accidents at non-intersections (2012 – 2016)
ITARDA INFORMATION no.125lSpeciafeatureRear-end collision accidents between four-wheel vehicles and bicycles~ Be careful not to overlook cyclists at night on the left-hand side of the roadway! ~ITARDA INFORMATION no.125

Rear-end collision accidents accounted for most

3 of the fatal accidents, with most of these occurring at night
Most fatal accidents occur on roadways, but what sorts of accidents must the cyclists be cautious of when riding
along roadways? Figs. 6 and 7 show the composition rates by type of accident for both casualty accidents and fatal
accidents between four-wheel vehicles and bicycles that occurred on roadways. Composition rate for type of
accident for casualty accidents indicates that various different accidents occur with relatively no significant
inclinations in any direction. Conversely, roughly half of fatal accidents consist of rear-end collision accidents at
48%, with their composition by accident type differing drastically from that for casualty accidents.

13％

2％

n＝213 accidents

22％

20％
n＝9,210 accidents

Angle collisions
Collisions whenturning left / right
Other

Fig. 7. Composition rate by type of accident
for fatal accidents on roadways (2012 – 2016)

Furthermore, the times at which accidents occur were divided up into day and night, with the composition rates foreach respective accident type shown in Figs. 8 – 11. Figs. 8 and 9 show the composition rates for the accident
types for both casualty accidents that occurred in the day and those that occurred at night. Rear-end collisions
account for a low rate of the casualty accidents that occurred during the day at just 5% of the total, but account for
17% of those that occurred at night. Moreover, looking at the composition for accident type for fatal accidents
indicated in Figs. 10 and 11 reveals that the rate of rear-end collisions was high both during the day and at night at
30% and 62% respectively.

Why is the rate of fatal accidents

As we have seen thus far, rear-end collision accidents on roadways account for a high rate of the fatal accidents
between four-wheel vehicles and bicycles, with a higher rate of such accidents occurring at night than in the day.
Therefore, the question is how dangerous are rear-end collision accidents compared with other types of accidents?
Fig. 12 shows the rate of fatal accidents (number of fatal accidents per 1,000 casualty accidents) by accident type
between four-wheel vehicles and bicycles that occurred on roadways over the 20-year period between 1997 and2016. While this fluctuates from year to year, the rate of fatal accidents from rear-end collisions is high on thewhole. The rate of fatal accidents from rear-end collisions has hovered between about 50 – 80%, whereas the rate
for the types of accidents other than rear-end collisions are below 20%.
Rear-end collisions

28％
4％

12％

n＝6,872 accidents

Fig. 8. Composition rate by type of accident
for casualty accidents during the day(2016; place of occurrence: roadways)
ITARDA INFORMATION no.125

60

70
61

60

59

52

56

65

63

54

56

50

46

56

64

63

65

62

54

54

40

20

n＝2,338 accidents

Fig. 9. Composition rate by type of accident
for casualty accidents at night(2016; place of occurrence: roadways)

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

20

20

20

20

20

20

20

20

20

20

20

20

20

20

0
20

Angle collisions
Collisions whenturning left / right
Other

01

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

20

Angle collisions
Collisions whenturning left / right
Other

19％

80

80

00

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Collisions when turning left / right

20

21％

Rate of fatal accidents

27％
21％

13％

Head-on collisions

Angle collisions

Collisions while passing / overtaking
100

17％

4％

Fig. 11. Composition rate by type of accident
for fatal accidents at night(2012 – 2016; place of occurrence: roadways)

4 from rear-end collision accidents so high?

5％29％

Angle collisions
Collisions whenturning left / right
Other

99

Fig. 6. Composition rate by type of accident
for casualty accidents on roadways (2016)

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Fig. 10. Composition rate by type of accident
for fatal accidents during the day(2012 – 2016; place of occurrence: roadways)

n＝484 accidents

Angle collisions
Collisions whenturning left / right
Other

Angle collisions
Collisions whenturning left / right
Other

19

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

48％

10％

n＝271 accidents

98

13％

62％

15％

14％

19

4％

3％

6％

32％

5％

26％

30％

11％

97

29％

16％

19

8％

5％

5％
1％

Years accidents occurredFig. 12. Rate of fatal accidents between four-wheel vehicles
and bicycles that occurred on roadways
ITARDA INFORMATION no.125lSpeciafeatureRear-end collision accidents between four-wheel vehicles and bicycles~ Be careful not to overlook cyclists at night on the left-hand side of the roadway! ~ITARDA INFORMATION no.125

Rear-end collision accidents accounted for most

3 of the fatal accidents, with most of these occurring at night
Most fatal accidents occur on roadways, but what sorts of accidents must the cyclists be cautious of when riding
along roadways? Figs. 6 and 7 show the composition rates by type of accident for both casualty accidents and fatal
accidents between four-wheel vehicles and bicycles that occurred on roadways. Composition rate for type of
accident for casualty accidents indicates that various different accidents occur with relatively no significant
inclinations in any direction. Conversely, roughly half of fatal accidents consist of rear-end collision accidents at
48%, with their composition by accident type differing drastically from that for casualty accidents.

13％

2％

n＝213 accidents

22％

20％
n＝9,210 accidents

Angle collisions
Collisions whenturning left / right
Other

Fig. 7. Composition rate by type of accident
for fatal accidents on roadways (2012 – 2016)

Furthermore, the times at which accidents occur were divided up into day and night, with the composition rates foreach respective accident type shown in Figs. 8 – 11. Figs. 8 and 9 show the composition rates for the accident
types for both casualty accidents that occurred in the day and those that occurred at night. Rear-end collisions
account for a low rate of the casualty accidents that occurred during the day at just 5% of the total, but account for
17% of those that occurred at night. Moreover, looking at the composition for accident type for fatal accidents
indicated in Figs. 10 and 11 reveals that the rate of rear-end collisions was high both during the day and at night at
30% and 62% respectively.

Why is the rate of fatal accidents

As we have seen thus far, rear-end collision accidents on roadways account for a high rate of the fatal accidents
between four-wheel vehicles and bicycles, with a higher rate of such accidents occurring at night than in the day.
Therefore, the question is how dangerous are rear-end collision accidents compared with other types of accidents?
Fig. 12 shows the rate of fatal accidents (number of fatal accidents per 1,000 casualty accidents) by accident type
between four-wheel vehicles and bicycles that occurred on roadways over the 20-year period between 1997 and2016. While this fluctuates from year to year, the rate of fatal accidents from rear-end collisions is high on thewhole. The rate of fatal accidents from rear-end collisions has hovered between about 50 – 80%, whereas the rate
for the types of accidents other than rear-end collisions are below 20%.
Rear-end collisions

28％
4％

12％

n＝6,872 accidents

Fig. 8. Composition rate by type of accident
for casualty accidents during the day(2016; place of occurrence: roadways)
ITARDA INFORMATION no.125

60

70
61

60

59

52

56

65

63

54

56

50

46

56

64

63

65

62

54

54

40

20

n＝2,338 accidents

Fig. 9. Composition rate by type of accident
for casualty accidents at night(2016; place of occurrence: roadways)

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

20

20

20

20

20

20

20

20

20

20

20

20

20

20

0
20

Angle collisions
Collisions whenturning left / right
Other

01

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

20

Angle collisions
Collisions whenturning left / right
Other

19％

80

80

00

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Collisions when turning left / right

20

21％

Rate of fatal accidents

27％
21％

13％

Head-on collisions

Angle collisions

Collisions while passing / overtaking
100

17％

4％

Fig. 11. Composition rate by type of accident
for fatal accidents at night(2012 – 2016; place of occurrence: roadways)

4 from rear-end collision accidents so high?

5％29％

Angle collisions
Collisions whenturning left / right
Other

99

Fig. 6. Composition rate by type of accident
for casualty accidents on roadways (2016)

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Fig. 10. Composition rate by type of accident
for fatal accidents during the day(2012 – 2016; place of occurrence: roadways)

n＝484 accidents

Angle collisions
Collisions whenturning left / right
Other

Angle collisions
Collisions whenturning left / right
Other

19

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

Rear-end collisions
Collisions while
passing / overtaking
Head-on collisions

48％

10％

n＝271 accidents

98

13％

62％

15％

14％

19

4％

3％

6％

32％

5％

26％

30％

11％

97

29％

16％

19

8％

5％

5％
1％

Years accidents occurredFig. 12. Rate of fatal accidents between four-wheel vehicles
and bicycles that occurred on roadways
ITARDA INFORMATION no.125lSpeciafeatureRear-end collision accidents between four-wheel vehicles and bicycles~ Be careful not to overlook cyclists at night on the left-hand side of the roadway! ~ITARDA INFORMATION no.125

Why is the rate of fatal accidents from rear-end collision accidents so high? Fig. 13 show the danger perception speedof four-wheel vehicles by accident type for casualty accidents between four-wheel vehicles and bicycles that occurredon roadways. The danger perception speed for when rear-end collision accidents occurred is higher than with otheraccident types. Roughly 60% of rear-end collision accidents consist of accidents where the vehicle had exceeded thedanger perception speed of 30km/h, with accidents where 50km/h had been exceeded accounting for more than 10%.
Rear-end collision accidents are an accident type whereby a four-wheel vehicle collides with a bicycle from behindwhen both the four-wheel vehicle and bicycle are traveling in the same direction. Therefore, it is conjectured that inmost cases accidents occurred because the four-wheel vehicle collided with the bicycle after a delay in detecting
them despite being in a position where the bicycle was visible up ahead for some time (this excludes cases where thebicycle suddenly cut directly in front of the four-wheel vehicle). Such cases result in the four-wheel vehicle colliding
with the bicycle after failing to reduce their speed by all that much, which is believed to be a factor behind the highrate of fatal accidents from rear-end collisions. Moreover, even in situations where rear-end collision accidents
occurred as a result of the bicycle cutting directly in front of the four-wheel vehicle, there is only a brief interval
between when danger is perceived and the collision, indicating that the vehicle is still traveling at a high rate of speed.
Over 50km/h

40km/h - 50km/h

30km/h - 40km/h

20km/h - 30km/h

10km/h - 20km/h

Less than 10km/h

5 Introduction to case examples of accidents
Two case examples of actual rear-end collisions between four-wheel vehicles and bicycles will be introduced.
The first accident consists of a rear-end collision accident that occurred when the driver failed to notice a bicycle atnight. This accident happened in lane one of a roadway with two-lanes in each direction around 23:00 at night. A
male in his 30s driving a medium-sized passenger car (A) was on his way home after finishing work. Given the lightvolume of traffic in the area due to the late hour, he was traveling approximately 70km/h in a section with a 60km/h
speed limit. There was a teenage girl traveling by bicycle (B) ahead of A in the same lane. B was returning homefrom school, and was on her way home from a station close to her house. Despite steadily drawing nearer to B, A
failed to detect B because his attention was focused on a traffic signal up ahead and he collided with B withoutslowing down at all.

Composition rate

100%
80%

3.0m

60%

A2

40%

3.0m

20%
0%

Rear-end
collisions

Collisions
while passing /overtaking

Head-oncollisions

Angle
collisions

Collisions
when turning
left / right

B2

Other

B1

Fig. 15. Rear-end collision accident that occurred because the driver failed to notice a bicycle

Fig. 13. Composition rates by dangerous perception speed for accidents between
four-wheel vehicles and bicycles that occurred on roadways (2016)
Fig. 14 shows the trends in the number of fatal accidents between four-wheel vehicles and bicycles that occurredon roadways each year in the 20 years between 1997 and 2016 for rear-end collision accidents and other types ofaccidents. In addition, the numbers in the diagram indicate the rate of rear-end collision accidents constituting thetotal number of fatal accidents. Even though the number of fatal accidents has been falling year by year, the rate ofrear-end collision accidents has risen moderately on the whole despite repeatedly fluctuating within a narrow band
since 2010. As indicated in Fig. 7, of the cumulative total from 2012 to 2016, rear-end collision accidents accounted
for roughly half of the fatal accidents between four-wheel vehicles and bicycles at 48%, accounting for 56% in the
single year of 2016. This indicates the immense importance of countering rear-end collision accidents between
four-wheel vehicles and bicycles.

The second accident consists of a rear-end collision accident that occurred because the driver failed to respondwhen the bicycle’s path changed. This accident also occurred at night sometime after 22:00 when a light rain was
falling. A medium-sized passenger car being driven by a male in his 20s (A) was traveling at approximately 50km/h
along a straight road with one-lane in one direction and a speed limit of 40km/h. A was aware of a bicycle being
ridden by a woman in her 60s (B) up ahead, but since she was riding in the sidewalk off to the left he continued
along without paying her much attention. After a short while, a parcel of private land jutted out from the left, causing
the sidewalk to gradually disappear. As a result, B’s path slowly moved towards the right as she followed along withthe straight line of the road, but A was slow in recognizing that B’s path had changed and collided with B.

250

Non-rear-end collision accidents
200

Rear-end collision accidents
150

A2

100
50

33％ 31％ 37％ 36％ 32％

31％

26％

38％

31％

38％ 32％ 39％ 38％
30％

49％

99

00

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

98
19

43％ 42％ 53％ 48％ 56％

19

97

0
19

Number of fatal accidents

A1

Years accidents occurredFig. 14. Number of fatal accidents between four-wheel vehicles
and bicycles that occurred on roadways
ITARDA INFORMATION no.125

B2

A1

B1

Fig. 16. Rear-end collision accident that occurred because the driver failed
to respond when the bicycle’s path changed
ITARDA INFORMATION no.125lSpeciafeatureRear-end collision accidents between four-wheel vehicles and bicycles~ Be careful not to overlook cyclists at night on the left-hand side of the roadway! ~ITARDA INFORMATION no.125

Why is the rate of fatal accidents from rear-end collision accidents so high? Fig. 13 show the danger perception speedof four-wheel vehicles by accident type for casualty accidents between four-wheel vehicles and bicycles that occurredon roadways. The danger perception speed for when rear-end collision accidents occurred is higher than with otheraccident types. Roughly 60% of rear-end collision accidents consist of accidents where the vehicle had exceeded thedanger perception speed of 30km/h, with accidents where 50km/h had been exceeded accounting for more than 10%.
Rear-end collision accidents are an accident type whereby a four-wheel vehicle collides with a bicycle from behindwhen both the four-wheel vehicle and bicycle are traveling in the same direction. Therefore, it is conjectured that inmost cases accidents occurred because the four-wheel vehicle collided with the bicycle after a delay in detecting
them despite being in a position where the bicycle was visible up ahead for some time (this excludes cases where thebicycle suddenly cut directly in front of the four-wheel vehicle). Such cases result in the four-wheel vehicle colliding
with the bicycle after failing to reduce their speed by all that much, which is believed to be a factor behind the highrate of fatal accidents from rear-end collisions. Moreover, even in situations where rear-end collision accidents
occurred as a result of the bicycle cutting directly in front of the four-wheel vehicle, there is only a brief interval
between when danger is perceived and the collision, indicating that the vehicle is still traveling at a high rate of speed.
Over 50km/h

40km/h - 50km/h

30km/h - 40km/h

20km/h - 30km/h

10km/h - 20km/h

Less than 10km/h

5 Introduction to case examples of accidents
Two case examples of actual rear-end collisions between four-wheel vehicles and bicycles will be introduced.
The first accident consists of a rear-end collision accident that occurred when the driver failed to notice a bicycle atnight. This accident happened in lane one of a roadway with two-lanes in each direction around 23:00 at night. A
male in his 30s driving a medium-sized passenger car (A) was on his way home after finishing work. Given the lightvolume of traffic in the area due to the late hour, he was traveling approximately 70km/h in a section with a 60km/h
speed limit. There was a teenage girl traveling by bicycle (B) ahead of A in the same lane. B was returning homefrom school, and was on her way home from a station close to her house. Despite steadily drawing nearer to B, A
failed to detect B because his attention was focused on a traffic signal up ahead and he collided with B withoutslowing down at all.

Composition rate

100%
80%

3.0m

60%

A2

40%

3.0m

20%
0%

Rear-end
collisions

Collisions
while passing /overtaking

Head-oncollisions

Angle
collisions

Collisions
when turning
left / right

B2

Other

B1

Fig. 15. Rear-end collision accident that occurred because the driver failed to notice a bicycle

Fig. 13. Composition rates by dangerous perception speed for accidents between
four-wheel vehicles and bicycles that occurred on roadways (2016)
Fig. 14 shows the trends in the number of fatal accidents between four-wheel vehicles and bicycles that occurredon roadways each year in the 20 years between 1997 and 2016 for rear-end collision accidents and other types ofaccidents. In addition, the numbers in the diagram indicate the rate of rear-end collision accidents constituting thetotal number of fatal accidents. Even though the number of fatal accidents has been falling year by year, the rate ofrear-end collision accidents has risen moderately on the whole despite repeatedly fluctuating within a narrow band
since 2010. As indicated in Fig. 7, of the cumulative total from 2012 to 2016, rear-end collision accidents accounted
for roughly half of the fatal accidents between four-wheel vehicles and bicycles at 48%, accounting for 56% in the
single year of 2016. This indicates the immense importance of countering rear-end collision accidents between
four-wheel vehicles and bicycles.

The second accident consists of a rear-end collision accident that occurred because the driver failed to respondwhen the bicycle’s path changed. This accident also occurred at night sometime after 22:00 when a light rain was
falling. A medium-sized passenger car being driven by a male in his 20s (A) was traveling at approximately 50km/h
along a straight road with one-lane in one direction and a speed limit of 40km/h. A was aware of a bicycle being
ridden by a woman in her 60s (B) up ahead, but since she was riding in the sidewalk off to the left he continued
along without paying her much attention. After a short while, a parcel of private land jutted out from the left, causing
the sidewalk to gradually disappear. As a result, B’s path slowly moved towards the right as she followed along withthe straight line of the road, but A was slow in recognizing that B’s path had changed and collided with B.

250

Non-rear-end collision accidents
200

Rear-end collision accidents
150

A2

100
50

33％ 31％ 37％ 36％ 32％

31％

26％

38％

31％

38％ 32％ 39％ 38％
30％

49％

99

00

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

98
19

43％ 42％ 53％ 48％ 56％

19

97

0
19

Number of fatal accidents

A1

Years accidents occurredFig. 14. Number of fatal accidents between four-wheel vehicles
and bicycles that occurred on roadways
ITARDA INFORMATION no.125

B2

A1

B1

Fig. 16. Rear-end collision accident that occurred because the driver failed
to respond when the bicycle’s path changed
ITARDA INFORMATION no.125

While the number of fatal accidents between four-wheel vehicles and bicycles continues to fall in andof itself, the rate of rear-end collision accidents of the fatal accidents that occur on roadways has
been trending upwards year by year. For this reason, countermeasures against rear-end collisions
between four-wheel vehicles and bicycles are growing more important with each passing year. The
regulations in the Road Traffic Act state that bicycles are to travel on the left side of roadways as a
general rule, and so people frequently encounter bicycles being ridden to the left of roadways whendriving automobiles. In order to enable bicycles to travel safely along roadways, we must respond toillegally-parked four-wheel vehicles that pose an obstacle to them. Furthermore, over the medium tolong-term we should ideally also improve the traffic environment for bicycles, including bicycle lanes
and other measures.

ITARDA INFORMATIONThis issue mainly looked at rear-end collision accidents which, out of all of the types of accidents
between four-wheel vehicles and bicycles, tend to lead to the most fatal accidents. Rear-end collision
accidents often occur when the driver of the four-wheel vehicle fails to notice a bicycle, and therefore
this is an accident type that should be handled from the four-wheel vehicle side. Both of the two caseexamples of accidents introduced occurred at night. In the first case, the driver was delayed in
detecting the bicycle because he was preoccupied by the traffic signal up ahead. In the second case,the accident occurred because even though the driver was aware of the bicycle, he failed to respondwhen the bicycle’s path changed. Both of these accident case examples occurred due to a lack ofattention being paid to a bicycle traveling in front of the driver.

交通事故分析レポート

6 Conclusion

TEL 03-5577-3973

FAX 03-5577-3980

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

ITARDA INFORMATION no.125

つくば 交通事故調査事務所

2

住 友 水 道 橋 ビル８ 階

渉外事業課

30

〒101 0064 東 京 都 千 代 田 区 神 田 猿 楽 町 ２ ７ ８イタルダインフォメーションに関するお問い合せ先

交通事故分析レポート No.125
Rear-end collision accidents between
four-wheel vehicles and bicycleslSpeciafeature~ Be careful not to overlook cyclists at nighton the left-hand side of the roadway! ~Number of fatal accidents per 1,000 casualty accidents
Rate of fatal accidents by type of accident between four-wheel vehicles
and bicycles that occurred on roadways*1(Cumulative total from 2012 to 2016)0.0

公益財団法人 交通事故総合分析センター(Akira Yamaguchi)

ITARDA INFORMATION

No.125

Seen from the perspective of four-wheel vehicles, bicycles are vulnerable road users. When driving
four-wheel vehicles, drivers must work to ensure that they drive safely when they detect bicycles
traveling along. Such efforts include paying attention to the bicycle’s movements and, when passingor overtaking them, maintaining as much distance between the bicycle as possible and reducing their
speed to one that is appropriate considering this distance when overtaking them.
On the other side, when it comes to measures to prevent accidents from the bicycle’s side, bicycles
are treated as a type of vehicle and granted the right to travel on roadways. In other words, cyclists
must abide by traffic signals and instructions to stop, as well as travel by obeying other traffic signs
and traffic rules. On top of this, to effectively respond to the rear-end collision accidents covered inthis issue, an approach that is considered to be effective even at night, when visibility is poor, is for
cyclists to equip themselves with equipment that emits light even without having the headlights fromfour-wheel vehicles shined on them. Examples of this include using reflective materials or installing
LED tail lights in order to alert drivers to their presence.

イタルダ インフォメーション

10.0

20.0

30.0

40.0

50.0

Rear-end
collisions
Head-oncollisions
Angle
collisions

60.0

70.0

60 accidents
9 accidents
7 accidents

Collisions
while passing/overtaking

4 accidents

Collisions
when turning
left / right1 accident*1. Rate of fatal accidents: Number of fatal accidents per 1,000 casualty accidents

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