ITARDA 26th Work Shop Report2023
26th Presentation Session for Traffic Accident Investigations, Analysis, and Research

Insights for reducing injuries and accidents derived from the latest trends in bicycle
accidents
Kenji Kawaguchi
Senior Researcher, Research Division

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ITARDA 26th Work Shop Report

Percentage of fatal and/or serious
injuries by parties concerned

1. Introduction
For the first time, a target for reducing serious injuries wasset forth in the 11th Basic Plan for Traffic Safety formulated inMarch 2021. The target set for serious injuries is 22,000 or lessby 2025 which, when combined with the target for fatalities of
2,000 or less, results in a combined target of 24,000 or less for

Other
Pedestrian
BicycleMopedMotorcycle
Fourwheeledvehicle

fatal and/or serious injuries. (Serious injury: An injuryYearrequiring 30 or more days of treatment.) In 2022, the totalFig. 1. Percentage of fatal and/or serious
injuries by circumstancenumber of fatal and/or serious injuries amounted to 28,637
persons, of which 23.4% were riding bicycles (6,702), showingthat the total percentage made up of bicycles is gradually
Various changes have been seen in recent trends surrounding
bicycle traffic, including an increase in the number of electricbicycles and sports bicycles that riders tend to ride at highspeeds, as well as the popularization of rental bicycles, shared

30 days

Bicycle rider fatalities

increasing (see Fig. 1).

24 hours
51%
increase
when added
to 30-dayfatalities for
2022

Year

bicycles, and of food delivery services that utilize bicycles. In
this paper, we will analyze the latest trends in bicycle accidents
from the following perspectives, and search for insights aimed

Fig. 2. Total number of fatalities in 24-hour and30-day periods (primary & secondary parties)at reducing accidents involving bicycles.
・ Overview and effects of wearing helmets(1)Number of 30-day
bicycle rider fatalities

・ Accidents involving single bicycles
・ Accidents involving pedestrians and bicycles
・ Accidents involving bicycles and passenger cars

Overall686

Non-head
Non-head

Head

567

Head

Percentage ofhead injuries

83%

2-1. Total number of fatalities and head injuries in 24-hourand 30-day periods
Looking at numbers bicycle rider fatalities, we can see that asignificant number of persons survived the initial 24 hours

75-84

85 andabove

65-74

55-64

45-54

35-44

25-34

19-24

16-18

13-15

12 andunder

2. Overview and effects of wearing helmets

Bicycle rider age

Fig 3. Most seriously injured part of the
body in 30-day fatalities (Head/Non-head)(2019 to 2022, primary + secondaryparties)

following the accident, but died within 30 days, causing thenumber of 30-day fatalities to be relatively high (see Fig. 2). Although the number of 24-hour fatalities is decreasing,
the number of 30-day fatalities has not decreased since 2020 and were equivalent to 51% of 24-hour fatalities in2022 alone.
When looking at the most seriously injured part of the body in 30-day fatalities, head injuries accounted for 83%(see Fig. 3). Because head injuries accounted for 55% of 24-hour fatalities, we can also assume that the percentageof 30-day fatalities made up by head injuries is also high. We can presume that there are many cases in which theinjured party hit their head and suffered serious enough injuries that they became unconscious and were unable to2ITARDA 26th Work Shop Report2-2. Effects of wearing helmets
When looking at fatality rate by helmet usage, it was observed thatwearing a helmet reduced the likelihood of the head being the mostseriously injured part of the body by 1/3, and also reduced the fatal

Asphyxiation,drowning, etc.
Legs

Percentage of bicycle rider fatalities

be saved. This fact highlights the importance of head protection.

Arms
LumbarBack
Abdomen
ChestNeckFace
Head
Wearing
helmetand/or serious injury rate by 1/2 (see Fig. 4 and Fig. 5).

Not wearing
helmetWhole bodyFig 4. Fatality rate by helmet usage &Most seriously injured part of the body(2019 to 2022, primary + secondary parties)
Wearing helmet: Helmet worn correctly

3. Accidents involving single bicycles
3-1. Casualty accidents involving single bicycles
on a decreasing trend until 2016, but started to rise again from around2017, and has been increasing rapidly in recent years (see Fig. 6). Suchaccidents have been increasing particularly in Tokyo, and this increase
seems to be due to an increased use in the types of bicycles mentioned
above.

Asphyxiation,drowning, etc.
Legs

Percentage of bicycle rider fatal
and/or serious injuries

The number of rider casualties in single-bicycle accidents had been

Arms
LumbarBack
Abdomen
Chest
Neck
Face
Head
Wearing
helmet3-2. Fatal accidents involving single bicycles
When looking at percentages of single-bicycle accidents by detailed
accident type, most serious and minor injuries were the result ofaccidents in which the rider or bike tipped over. However, 65%, or

Not wearing
helmetWhole bodyFig 5. Fatal and/or serious injury rates byhelmet usage &Most seriously injured part of the body(2019 to 2022, primary + secondary parties)

approximately 2/3rds, of fatalities
the bicycle fell from an elevatedheight (see Fig. 7).
Furthermore, when looking at thepart of body that suffered the mostserious injury in the event of a fallingNumbers of rider casualties
in single-bicycle accidents

were the result of accidents in which

accident, suffocation and drowningaccounted for 49% of fatalities,
followed by injuries to the neck at
27% (see Fig. 8). This highlights theFig. 6. Numbers of rider casualties in single-bicycle accidents

need for riders to be more careful of their forward direction when riding in areas where waterways such as irrigation
ditches are common. The fatality rate in the event of a falling accident was 56%, or more than one in two riders,
while the fatal and/or serious injury rate was also extremely high at 76% (see Fig. 9).

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ITARDA 26th Work Shop Report
Other
Tipping overAsphyxiation,drowning, etc.
Legs

Off-road deviation- Other
Off-road deviation- FallParked vehicle
Man-madestructure - Other
Bridge pier/spanTipping overFall

Arms
LumbarBack
AbdomenHouse/wall/fence
Protective barrier,etc.

ChestDivider, etc.

Face
Head

Sign
Minor
injurySerious
injuryFatality

Percentageof fatalities

Neck

Whole body

Utility poleFig. 7. Single-bicycle accidents by detailed
accident type
(Bicycle riders, 2019 to 2022)

Serious
injuryFatality

Minor
injuryFig. 8. Most seriously injured
part of the body in single-bicycle
falling accidents by percentage(Bicycle riders, 2019 to 2022)

Fig 9. Fatality rate in falling
accidents
Percentage of fatal and/orserious injury(Bicycle riders, 2019 to 2022)

4. Accidents involving pedestrians and bicycles
4-1. Trends in recent years
From here on, we will look at
accidents in which pedestrians
wereinjured

incollision

accidents with bicycles. Figure
10 shows trends for numbers ofYear

pedestrian fatal and/or serious
injuries.

Althoughsuch

accidents increased from 2016,
they decreased in 2019 and haveremainedflat

sincethen.

Similarly,

thenumberofYear

Fig. 10. Number of pedestrian fatal
and/or serious injuries(Bicycle-pedestrian accidents,primary + secondary parties)

Fig. 11. Number of pedestriancasualties(Bicycle-pedestrian accidents,primary + secondary parties)

pedestrian casualties decreased
temporarily in 2020, but thenstarted to increase again (seeOsakaTokyoTokyo

Osaka

Fig. 11).
Shown here are trends forTokyoandOsaka,

which

account for a large proportion ofpedestrian

fatalities

amongFig. 12. Numbers of pedestrian fatal
and/or serious injuries

Fig. 13. Number of pedestriancasualties

Tokyo and Osaka (Bicycle-pedestrian accidents,primary + secondary parties)

prefectures in Japan (see Fig.
12). Since 2017, the number of pedestrians who suffered fatal and/or serious injuries has increased rapidly.
Furthermore, the number of pedestrian casualties in Tokyo has started increasing since 2017, and tends to be similar
to those for bicycles seen in Fig. 6 (see Fig. 13). Furthermore, the number of pedestrian casualties in Tokyo has4

ITARDA 26th Work Shop Report

started increasing since 2017, and tends to be similar to those for bicycles seen in Fig. 6 (see Fig. 13). In other words,
if a cyclist rides at a high speed or drives without paying attention in the forward direction and collides with astructure, etc., it results in a “single-bicycle accident”. Instead, if they collide with a pedestrian, it results in a“bicycle-pedestrian accident”.

population density
Figure 14 shows the population
density by prefecture and thenumber of pedestrian casualties per
100,000 people. While not a simple
linear relationship, it is evident thatthe higher the population density,

30 daysTokyo

Fukuoka Chiba
HyogoAichi
Osaka
Kanagawa

Okinawa

Saitamawith bicycles per 100,000 people.
In cities with high population

Fig. 14. Population density and numbers ofpedestrian casualties due to bicycle-pedestrian
accidents per 100,000 people(2019 to 2022, primary + secondary parties)

densities, it is necessary for riders

164%
increase

Total

Population density (Pop./km2)

the greater the number of pedestriancasualties resulting from collisions

24 hours

Pedestrian fatalities due toaccidents with bicycles(1) Relationship with

Numbers of pedestrian fatalities and/orinjuries due to bicycle-pedestrian
accidents per 100,000 people

4-2. Characteristics of accidents

Fig. 15. Numbers ofpedestrian fatalities due
to bicycle-pedestrian
accidents(2017 to 2022, primary +secondary parties)

to ride their bikes in a pedestrian-friendly manner.
(2) Pedestrian fatalities
Figure 15 shows the number of pedestrians who died as a result of a collision with a bicycle. Although 24-hour
fatalities over the six-year period from 2017 totaled 17 people, 30-day fatalities were high at 28 people, indicatingthat many people died after the initial 24-hour period following the accident.
5. Accidents involving bicycles and passenger cars
Finally, we will look at accidents between bicycles and passenger cars from the perspective of passenger cars inorder to clarify whether newer passenger car models are involved in fewer accidents with bicycles. Conditions of・ Full Model Change Year (Mo.CY) 2011-2020 (Note that
this is not equivalent to the first year in which the model
was registered.)・ Vehicle types with both hybrid models (HEV) and nonhybrid (CE) models

Numbers of bicycle rider
casualty accidents per 10,000
vehicles registeredthe vehicle types selected here are as follows:

22 vehicle types without HEV

・ Vehicle types with 40,000 or more total registered vehicles
over the four-year analysis period from 2019 to 2022
As a result of these conditions, 22 vehicle types wereselected and analyzed, enabling a decreasing trend to be5Fig. 16. Trends in numbers of casualty
accidents involving bicycles per 10,000
vehicles owned by Mo.CY(2019 to 2022, primary + secondary parties)

ITARDA 26th Work Shop Reportconfirmed for newer vehicle types. (see Fig. 16). However, when comparing models of the same vehicle, it wasobserved that HEV models tended to be involved in more accidents with bicycles, regardless of Mo.CY (see Fig.
17). Furthermore, when comparing HEV models to CE models in terms of rates of accidents involving bicycles,
HEV model rates exceeded those of CE models by 100% in the case of almost all 22 vehicle types (see Fig. 18).
Because both HEV and CE models have the same vehicle body design, and therefore the same direct visibility andpreventive safety systems, it can only be assumed that because the engines are different, that engine noise may be
the cause for this. It is possible that further research and technological developments may bring levels of accidents
between HEVs and bicycles down to those of CE.

Fig. 17. Comparison of HEV and CE interms of numbers of casualty accidents
involving bicycles per 10,000 vehicles
owned(2019 to 2022, primary + secondaryparties)

Fig. 18. Ratio of HEV to CE in terms of numbers ofcasualty accidents involving bicycles per 10,000
vehicles owned(2019 to 2022, primary + secondary parties)

6. Summary(1) Compared to other circumstances, the rate of bicycle rider fatalities over a 30-day period is high, with over
80% being due to head injuries. Wearing a helmet greatly reduces the chance of fatal and/or serious injuries
due to head injury.
(2) Number of casualty accidents involving single bicycles is increasing rapidly, mainly in Tokyo. Falling
accidents account for 2/3 of all fatal accidents involving single bicycles, with suffocation and drowningaccounting for 49% of these deaths, while accidents in which the neck was most seriously injured part of thebody also accounting for a large portion at 27%.
(3) Numbers of pedestrian fatal and/or serious injuries due to collisions with bicycles remains flat, while numbersof pedestrian casualties is on the rise. Particularly in cities with high population densities, it is necessary for
riders to ride their bikes in a pedestrian-friendly manner.
(4) Although newer models of passenger cars tend to be involved in fewer accidents involving bicycles, hybrid
models are involved have more such accidents than non-hybrid models, and there are expectations that future
research can help reduce such accidents with bicycles.
<Source>(1) 2022, ITARDA Information (No.144), “Head injuries and the effects of helmets in bicycle accidents”

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