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

Utilizing Data from Event Data Recorders and Dashboard cameras for Micro-level
Surveys
Motoki Sugiyama
Investigator, Investigation Dept., Tsukuba Traffic Accident Investigation Office0ITARDA 26th Work Shop Report

1.

Introduction
In finding measures for preventing the recurrence of traffic accidents and mitigating damage, it is necessary tocollect as much information and data on accidents as possible, after which that information and data must be
analyzed both scientifically and comprehensively in order to investigate the causes of accidents. Also, wheninvestigating the cause of an accident, it is necessary to reproduce accident conditions as accurately as possible.
In micro-level surveys conducted by the Institute for Traffic Accident Research and Data Analysis (hereinafter,“ITARDA”), accident conditions are reproduced by using collected information and data to create a situation mapthat shows the situation before and after a collision on a road diagram of the accident site.
Furthermore, in recent years, vehicle reference information has been collected by event data recorders (hereinafter,“EDRs”) in the form of chronological data including pre- and post-collision vehicle behavior and driver operation
status, as well as by dashboard cameras in the form of footage showing the road traffic environment surrounding
vehicles. Using these data to reproduce accident situations makes it is possible to create drawings (hereinafter,“reconstruction diagrams”) that add objective information to situation maps, such as vehicle behavior immediately
prior to a collision, driver operation status, and the road traffic environment surrounding vehicles.
The purpose of this research was to improve ITARDA's accident analysis technology by creating reconstruction
diagrams using data from two actual accident case studies and by examining accident analysis methods using thesereconstruction diagrams.
2.

Reconstruction methods

2-1. Data recorded from EDRs
Data recorded from EDRs is categorized as either pre-crash or post-crash data, with the timestamp at which thecollision was detected serving as the reference point. In this research, pre-crash data was used for reconstruction
diagrams. Pre-crash data records several types of information in the form of chronological data, such as vehicle
behavior immediately prior to an accident, driver operation status, and the operation status of electronic vehicle
control systems. Examples of such information include vehicle speed, yaw rate, service brake ON/OFF status, aswell as various data such as that regarding the operation status of the anti-lock braking system (hereinafter, “ABS”)
and collision damage mitigation braking system (hereinafter, “AEB”). Furthermore, during this research, service
brake ON status refers to when the brake pedal is pressed, while service brake OFF status refers to when the brake
pedal is not pressed.
Overview of reconstruction
diagram creation

2-2. Creating reconstruction diagrams

EDR

During this research, a vehicle equipped with an*Event data recorder

Travel trajectory

EDR and dashboard camera was used to reproduce theDashcamsituation before a collision when the vehicle*Dashboard camera

encountered an accident. Figure 1 shows an overview
Situation
mapof how reconstruction diagrams are created.
In Step 1, the vehicle's travel trajectory was

Travel trajectory+
Dashcam images

Travel trajectory + Dashcam images+
Road diagram (road environment, etc.)
Reconstruction diagram

calculated using the pre-crash data. In this calculation

Fig. 1 Overview of reconstruction diagram creation

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method (1), the vehicle speed and yaw rate are integrated for each timestamp of the pre-crash data, enabling thetravel trajectory before the collision to be estimated. Also, the positions of each point on the estimated travel
trajectory correspond one-to-one with each timestamp of the pre-crash data. For this reason, the position of eachpoint for the travel trajectory is linked with recorded data for each timestamp of the pre-crash data. Furthermore, inthis research, the positions of vehicle parts at each point of the travel trajectory are assumed to correspond to theinstallation location of the yaw rate sensor.
In Step 2, dashboard camera images are combined with each trajectory point of the travel trajectory estimated in
Step 1. The timestamp of the moment at which the collision is detected in the pre-crash data is set as zero. The precrash data and dashboard camera video are then synchronized by aligning this zero-timestamp with the timestamp
for moment in the video recorded by the dashboard camera in which the vehicle is assumed to have collided. Next,
images from the dashboard camera that correspond to each timestamp in the pre-crash data are extracted andmatched with the points of each trajectory point of the travel trajectory.
In Step 3, the travel trajectory from Step 2 is projected

Yaw rate sensor
installation location

Positional relationshiponto the situation map. As shown in (1) of Figure 2, theArea subject
to collisionarea of the vehicle subject to collision is identified from

Traveltrajectory

the vehicle investigation results, after which the location

Situation mapof the yaw rate sensor and the positional relationship withthe vehicle center line (α) is confirmed from vehicle

Area R

specifications, etc.

Area I

In order to match this positional relationship with thetravel trajectory, a straight line (β) passing through two
Area R

points (one at the time of collision and one at the

Area I

timestamp just before the collision) is obtained. The
location of the yaw rate sensor is then adjusted to theFig. 2 Travel trajectory projection method[Step 3]point at the time of collision, and vehicle center line (α)
is matched with straight line (β).

As shown in (3) of Figure 2, the location near where the vehicles are thought to have collided (hereinafter, “AreaI”) is determined on a drawing of the situation map using information taken from interviews of the drivers involvedin the accident and images recorded by the dashboard camera. Area I is a projection onto the ground surface of thearea of the vehicle subjected to collision when the vehicle collision occurred. Additionally, the area where theinstallation location of the vehicle yaw rate sensor passed within the range traveled from 5 seconds before thecollision detection timestamp until the collision detection timestamp (hereinafter, “Area R”) is obtained from thedashboard camera video.
Finally, as shown in (4) of Figure 2, the travel trajectory is projected onto drawing of the situation map, byaligning area of the vehicle subjected to collision with Area I so that the points of the travel trajectory before thecollision pass through Area R.

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ITARDA 26th Work Shop Report3.

Applying

reconstruction

methods

toaccident case studies

Vehicle A

Vehicle B

Type

Medium-sized
passenger vehicle

Mini-vehicle

Year firstregistered

March 2020

April 2012

EDR

Yes

No

DashcamYes

Yes

3-1. Applying reconstruction methods to Case
Study 1Figure 3 shows the accident summary and situation
map for Case Study 1. Case Study 1 involved an
accident at an intersection with traffic lights in
which

a

right-turning

four-wheeledvehicle(hereinafter, “Vehicle A”) collided with a straightmoving four-wheeled vehicle (hereinafter, “Vehicle

Four-wheeled vehicle
× Four-wheeled vehicle

Accident
category

AEB
installation

Yes

No

Occupant

70 years
old woman

60 years
old woman

Accident type

Right-turn against accident

Accident overview
While turning right from the right lane at a crossroadintersection with traffic lights, Vehicle A collided with
Vehicle B, which was going straight in the first lane ofthe opposite direction.
SIP accident patternB”) on a road with two lanes in each direction
intersecting a road with four lanes in each direction.

Fig. 3 Accident summary and situation map for Case
Study 1After waiting to turn right, Vehicle A commenced its right turn by following the preceding vehicle, at which time itcollided with Vehicle B, which was proceeding straight in the opposing lane. In this case, Vehicle A was a mediumsized passenger vehicle, while Vehicle B was a mini-vehicle. Vehicle A was equipped with an EDR, dashboard
camera and AEB functions, while Vehicle B was only equipped with a dashboard camera.
During an interview, the driver of Vehicle A stated, "I started to turn right after the car in front of me, after which
I collided with the oncoming vehicle (Vehicle B), which was making a right turn.” Because the driver did not notice
the oncoming vehicle until the collision occurred, they could not brake or steer to avoid the collision. The driver
also stated that they thought the automatic brakes may have operated. In this case, an interview with the driver of
Vehicle B could not be obtained.
3-2. Reconstruction results for Case Study 1
Figure 4 shows the estimated travel trajectory

Collision
detection time

obtained using the pre-crash data of the EDR of Vehicle
A using the method shown in Step 1 of 2-2. The point of
the travel trajectory at 0.00 sec. in Figure 4 indicated thetimestamp for the moment the vehicle collision was
detected. Also, Figure 5 shows a reconstruction diagram
for Vehicle A obtained using the method shown in 2-2.

Fig. 4 Travel trajectory of Vehicle A in Case Study 1

Figure 5 shows a portion of the pre-crash data(timestamps, vehicle speed, and ON/OFF statuses of theservice brake, ABS, and AEB) and images from the dashboard camera for each point of the travel trajectory once
the traffic light turned yellow, starting from -2.25 seconds. The yellow boxes in the dashboard camera images show
the vehicle ahead of Vehicle A while the blue boxes show Vehicle B.
The data for each point shown in Figure 5 are as follows:
・ The vehicle speed was approximately 22 km/h at -2.25 seconds, approximately 25 km/h at -1.75 seconds,
approximately 27 km/h at both -1.25 and -0.75 seconds, approximately 26 km/h at -0.25 seconds, and3

ITARDA 26th Work Shop Reportapproximately 15 km/h at 0.00 seconds.
・ The service brake was OFF from -2.25 seconds to*Traffic light: Yellow*Traffic light: Red*Traffic light: Red*Traffic light: Red*Traffic light: Red*Traffic light: Red-0.75 seconds, and ON from -0.25 seconds to 0.00
seconds.
・ The ABS was OFF between -2.25 seconds and 0.25 seconds, and ON at 0.00 seconds.
・ The AEB was OFF for the entire time from -2.25
seconds to 0.00 seconds.
・ The traffic light in the front of the vehicle was
yellow at -2.25 seconds, but red between -1.75 and0.00 seconds.

Fig. 5 Reconstruction diagram for Vehicle A in Case
Study 13-3. Applying reconstruction methods to Case
Study 2
Figure 6 shows the accident summary and situation map for Case Study 2. Case Study 2 involved a crossing
collision between two four-wheeled vehicles at an intersection.
In this case, Vehicle A was a mini-vehicle, while
Vehicle B was a medium-sized passenger vehicle.
Vehicle B was equipped with an EDR, dashboard
camera and AEB function.

Four-wheeled vehicle
× Four-wheeled vehicle

Accident
category

Vehicle A

Vehicle B

Type

Mini-passenger
vehicleMedium-sized
passenger vehicle

Year firstregisteredMay 2009

April 2021

EDR

No

Yes

DashcamNo

Yes

Accident type

Crossing collision

In an interview with the driver of vehicle A, theystated, "I stopped inside the intersection to make aright turn and collided with Vehicle B". Furthermore,in an interview with the driver of Vehicle B, theystated,"Whenentering

theintersection

atapproximately 60 km/h, I felt a sense of danger andAEB
installation

No

Yes

Occupant

50 years
old woman

30 years
old manAccident overview
While turning right at a crossroad intersection withstop signs, Vehicle A collided with Vehicle B, which
was proceeding forward from the right side.
SIP accident patternapplied the brakes, but ended up colliding with theFig. 6 Accident summary and situation map for Case
Study 2other vehicle. Also, I don’t think the AEB operated
when the accident occurred”.
3-4. Reconstruction results for Case Study 2

In Case Study 2, Figure 6 shows a reconstruction diagram for Vehicle B obtained using the method shown in 22.
Also, Figure 7 shows an image of when the vehicle started to enter the intersection.
This figure shows a portion of the pre-crash data (timestamps, vehicle speed, and ON/OFF statuses of the service
brake, ABS, and AEB) and images from the dashboard camera for each point of the travel trajectory starting from 1.70 seconds. The red boxes in the dashboard camera images show Vehicle A, which collided with Vehicle B. Also,
the reconstruction diagram in Figure 6 shows data starting from -1.70 seconds.

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ITARDA 26th Work Shop Report

The data for each point shown in Figure 7 are as follows:
・ The vehicle speed was approximately 56 km/h at 1.70 seconds, approximately 56 km/h between -1.20
seconds and -0.20 seconds, and approximately 54
km/h at -0.00 seconds.
・ The service brake was OFF from -1.70 seconds to 0.70 seconds, and ON from -0.20 seconds to 0.00
seconds.
・ The ABS was OFF for the entire time from -1.75
seconds to 0.00 seconds.
・ The operating status of the AEB was not included inFig. 7 Reconstruction diagram for Case Study 2

the pre-crash record for Vehicle B. For this reason,
we checked the audio recorded by the dashboard camera of Vehicle B, and because no warning sounds could beheard from this recording, it is assumed that the AEB did not operate before the collision.
4.

Examining accident analysis methods using reconstruction results

4-1. Estimating driver danger perception speed
When investigating and analyzing accidents, theApprox.
0.6 sec

vehicle speed at which the driver perceives danger

Approx.
0.5 sec(danger perception speed) is an important value, such as

Approx.
0.5 sec

for when the probability of death or serious injury is

Dangerperceived bydriverestimated by the automatic emergency call system (Dcall net). However, in many cases, information on thedanger perception speed cannot be obtained frominterviews with drivers, which is a problem when

Fig. 8 Danger perception speed of driver of
Vehicle A in Case Study 1collecting information during accident investigations.
Therefore, in this research, we estimated the driver’s
danger perception speed in the reconstruction diagramsfor Case Studies 1 and 2.

As mentioned in 3-1, the driver of Vehicle A in Case Study 1 stated, “I could not brake because I didn’t notice
Vehicle B until the collision occurred”. However, in the reconstruction diagram shown in Figure 5, because theservice brake was ON at -0.25 seconds, it is conceivable that the service brake was ON between -0.75 seconds and-0.25 seconds. If we assume that activation of the service brake (service brake ON status) is a result of the driverperceiving danger, and relying upon the literature (2) which suggests a reaction time of approximately 0.6 seconds
from the driver's danger perception until the driver starts pressing braking pedal, it can be assumed that the driverof Vehicle A perceived danger between -1.35 seconds and -0.85 seconds. Therefore, as shown in Figure 8, the danger
perception speed was estimated to be 25 km/h or 27 km/h, which was the vehicle speed at timestamps for the three
pre-crash data (-1.75 seconds, -1.25 seconds, -0.75 seconds) including this time range.

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ITARDA 26th Work Shop Report

In Case Study 2, the danger perception speed of the driver of Vehicle B was estimated using the reconstruction
diagram.
As mentioned in 3-3, the driver of Vehicle B stated, "IApprox.
0.6 secentered the intersection at approximately 60 km/h".

Approx.
0.5 sec

Accordingly, the information gained from the interview led

Approx.
0.5 sec

to the danger perception speed being estimated asDangerperceived bydriverapproximately 60 km/h.
In the reconstruction diagram shown in Figure 7, theservice brake status was ON at -0.20 seconds.
Accordingly, it is conceivable that the service brake of

Fig. 9 Danger perception speed of driver of
Vehicle A in Case Study 2

Vehicle B was ON between -0.70 seconds and -0.20
seconds. Using the same method as that from Case Study
1, it is conceivable that the driver of Vehicle B perceived

danger between -1.30 seconds and -0.80 seconds. Therefore, as shown in Figure 9, the danger perception speed wasestimated to be 55 km/h or 56 km/h, which was the vehicle speed at timestamps for the three pre-crash data (-1.70
seconds, -1.20 seconds, -0.70 seconds) including this time range. From this, we can see that in Case Study 2 there
was a difference of approximately 5 km/h between the danger perception speed stated by the driver of Vehicle B
and the figure obtained from the reconstruction diagram. If we consider that the danger perception speed stated by
the driver is rounded to the nearest 5 km/h (using cash rounding), a difference of approximately 5 km/h is notconsidered significant.
The above suggests that estimations of driver danger perception speeds can be inferred through the use ofreconstruction diagrams.
4-2. Analysis of AEB operation status
Using the reconstruction diagrams from Case Studies 1 and 2, we analyzed the operation status of the vehicle
AEB systems.
As seen in 3-2 and 3-4, the AEB did not operate for Vehicle A in Case Study 1 or Vehicle B in Case Study 2. To
find the reason why the AEB failed to operate, we examined the conditions made evident from resources such asreconstruction diagrams, as well as the AEB operating conditions listed in the specifications of each vehicle’s
owner’s manual.
Table 1 shows the AEB operating conditions for Vehicle A in Case Study 1 when turning right and was takenfrom the specifications (3) shown in the vehicle’s owner’s manual.
The reconstruction diagram in Figure 5 shows that

Intersection turning assistance (pre-crash brake)

the speed of Vehicle A before the start of braking (-0.75
seconds) was approximately 27 km/h, while the video
recorded by the dashboard camera estimated the speedof Vehicle B before the collision to be approximately

Operation
targetOwn vehicle
speed

Oncoming vehicle
speed

Relative speed

VehicleApprox. 15 to 25
km/h

Approx. 30 to 45
km/h

Approx. 45 to 70
km/h

Table 1. AEB operating conditions of Vehicle A in
Case Study 1

45 km/h.
Based on this information, it conceivable that the6

ITARDA 26th Work Shop Report

AEB did not operate because the relative speed of Vehicles A and B at the start of braking was approximately 72
km/h, which was outside the specified range for AEB operating conditions (approx. 40 km/h to 70 km/h).
Furthermore, as shown by the dashboard camera images in Figure 5, because Vehicle B could not be seen by thedriver of Vehicle A until -1.25 seconds due to the vehicle in front of Vehicle A, detection of Vehicle B by the forwardfacing sensors and camera of Vehicle A was delayed, or was not possible.
Table 2 shows the normal AEB operating conditions

Pre-crash brakefor Vehicle B in Case Study 2 and was taken from theOperation target

specifications (4) shown in the vehicle’s owner’s

Vehiclemanual.
The reconstruction diagram in Figure 6 shows thatOwn vehicle speed

Relative speed

Approx. 15 to 25 km/h Approx. 45 to 70 km/h

Table 2. AEB operating conditions of Vehicle B in
Case Study 2

the speed of Vehicle B before the start of braking wasapproximately 56 km/h, while the relative speed of

Vehicles A and B was approximately 56 km/h, which both fall within the specified range for AEB operating
conditions (approximately 10 km/h to 180 km/h). However, according to the specifications (4) listed in the owner’s
manual of Vehicle B, it states, “the AEB system may not operate properly when approaching a vehicle in front thatis facing sideways or in the direction of your vehicle”. Because this description may be applied to the situation inCase Study 2, it is possibly the reason why the AEB did not operate in the case of this accident.
5.

Conclusion
The purpose of this research was to improve accident analysis capabilities by creating reconstruction diagrams

using data from EDRs and dashboard cameras for use in actual accident case studies and by examining accident
analysis methods using these reconstruction diagrams.
・ The creation of reconstruction diagrams enabled us to use pre-crash data linked to each trajectory point of thevehicle travel trajectory to show information on vehicle control, such as vehicle speeds and service brake on/off
statuses. Also, from the dashboard camera images at the time of the accident, we were able to confirm the roadtraffic environment surrounding the vehicle.
・ Our study of accident analysis methods using reconstruction diagrams enabled us to show a method of estimating
the driver danger perception speed and an method of analyzing the AEB operation status.
6.

Sources1)

H. Matsumura, T. Itoh: “Study on Estimation of Traveling Trajectory Using the Recording Data in the Event
Data Recorder“, SAE International Journal of Advances and Current Practices in Mobility, 5(2): 580-594,
2023DaJapan Society of Traffic Engineers: Road Traffic Essentials 2018, p.58-59 (2018)https://manual.toyota.jp/yaris/
https://manual.toyota.jp/corollacross/

2)
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4)

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