SEPTEMBER 2022

AUTOMATIC EMERGENCYBRAKING PERFORMANCEIN THE CONTEXT OFCOMMON CRASH SCENARIOSNewsRoom.AAA.com

Evaluation of Automatic Emergency Braking Systems(this page intentionally left blank)© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

ABSTRACTIn collaboration with the National Highway Traffic Safety Administration (NHTSA), twenty automakers havevoluntarily agreed to equip their passenger vehicles with Automatic Emergency Braking (AEB) systems as
standard equipment by September 1, 2022. As these systems become commonplace on new vehicles, it isimportant that consumers understand system performance and limitations in a variety of common scenarios.
To evaluate the performance of current AEB systems, four popular vehicles equipped with an AEB system asstandard equipment were evaluated in a variety of common scenarios within a closed-course environment.
Research Questions:
1. How do evaluated AEB systems perform when encountering a stationary vehicle ahead at speeds of 30
and 40 mph?
2. How do evaluated AEB systems perform when encountering moving vehicles in collision scenarios
involving an intersection?
a. Test and target vehicles in a perpendicular collision scenario (T-bone)b. Test vehicle turning left in front of oncoming target vehicle (Unprotected left turn)
Key Findings:
1. How do evaluated AEB systems perform when encountering a stationary vehicle ahead?
a. At a steady-state approach speed of 30 mph, evaluated AEB systems prevented a collision for 17
of 20 test runs, in aggregate. For test runs that resulted in a collision, the impact speed was
reduced by an average of 86 percent.
b. At a steady-state approach speed of 40 mph, evaluated AEB systems prevented a collision for 6of 20 test runs, in aggregate. For test runs that resulted in a collision, the impact speed was
reduced by an average of 62 percent.
2. How do evaluated AEB systems perform when encountering moving vehicles in collision scenarios
involving an intersection?
a. For a perpendicular collision scenario, an unmitigated collision occurred for 100 percent of test
runs, in aggregate.
b. For a collision scenario involving a left turn in front of an oncoming vehicle, an unmitigatedcollision occurred for 100 percent of test runs, in aggregate.

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CONTENTSI.

INTRODUCTION ................................................................................................................................... 6

II. BACKGROUND..................................................................................................................................... 7
III. VEHICLE SELECTION METHODOLOGY ........................................................................................... 11
IV. TEST EQUIPMENT AND RESOURCES ............................................................................................. 11
A.

Vehicle Dynamics Equipment ......................................................................................................... 111.

Oxford Technical Solutions (OxTS) RT3000 V2 with RT-Range Hunter .......................................... 11

2.

Futek LAU220 Pedal Force Sensor ................................................................................................. 123.

DEWESoft CAM-120 Cameras with CAM-BOX2 Distribution Box ................................................... 124.

DEWESoft CAN-2 Interface ............................................................................................................ 13

5.

Data Logging Equipment ................................................................................................................. 13

6.

DRI Low Profile Robotic Vehicle (LPRV) with DRI Soft Car 360® ................................................... 13

B.

Test Facility .................................................................................................................................... 14

V. VEHICLE PREPARATION .................................................................................................................. 16
VI. INQUIRY 1: How do common AEB systems perform when encountering a stationary vehicle ahead? 17
A.

Objective ........................................................................................................................................ 17

B.

Methodology ................................................................................................................................... 17

C. Test Results ................................................................................................................................... 18
1.

30 mph Rear AEB Test Scenario .................................................................................................... 18

2.

40 mph Rear AEB Test Scenario .................................................................................................... 22

D. Discussion ...................................................................................................................................... 26VII. INQUIRY 2: How do common AEB systems perform when encountering moving vehicles in collision
scenarios involving an intersection? .......................................................................................................... 27
A.

Objective ........................................................................................................................................ 27

B.

Methodology ................................................................................................................................... 27
1.

Perpendicular (T-bone) collision scenario ....................................................................................... 28

2.

Test vehicle turning left in front of oncoming target vehicle ............................................................. 29

C. Test Results ................................................................................................................................... 31
1.

Perpendicular (T-bone) collision scenario ....................................................................................... 31............................................................................................................................................................... 31
2.

Test vehicle turning in front of oncoming target vehicle ................................................................... 32

D. Discussion ...................................................................................................................................... 33© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

VIII.

CONCLUSIONS ............................................................................................................................. 33

IX. KEY FINDINGS ................................................................................................................................... 34
X. RECOMMENDATIONS ....................................................................................................................... 34
XI. REFERENCES .................................................................................................................................... 35
XII. APPROVALS ...................................................................................................................................... 36© 2022 American Automobile Association, Inc.

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I. INTRODUCTION
Automatic Emergency Braking (AEB) systems were first introduced on the Japanese-market Honda Inspirewith its Collision Mitigation Brake System and the Mercedes-Benz S-Class with PRE-SAFE®, both in 2003.
Since then, AEB has become increasingly common on vehicles across various price points. This progress
was escalated on March 17, 2016, when NHTSA and the Insurance Institute for Highway Safety (IIHS)
announced a voluntary commitment by twenty automakers, representing more than 99 percent of the U.S.
auto market, to make AEB standard across their vehicle lineup by September 1, 2022 [1]. According toConsumer Reports, 83 percent of 2022 model year vehicles sold in the U.S. are equipped with AEB as
standard equipment. This number substantially grown during recent years; likely a result of preparations
required to meet the commitment date. For context, only 31 percent of 2018 model year vehicles came with
AEB as standard equipment. In addition to increasing standardization in new vehicles, the prevalence of AEB
systems will continue to increase as older vehicles are retired.

Image Source: AAA

Widespread inclusion of AEB across the U.S. vehicle fleet has the potential to prevent a significant number of
injuries and fatalities. Previous research by IIHS found that vehicles equipped with AEB exhibited a 50
percent decrease of police-reported rear-end crashes relative to equivalent vehicles without an AEB system[2]. These data take into account police-reported rear-end crashes with or without injury in twenty-two states
during 2010–2015 for six makes.
This documented reduction in rear-end crash rates are specific to considerably earlier forms of AEB in termsof age as well as refined hardware and software design iterations released since. It could be hypothesizedthat current AEB systems like those characterized in this work would exhibit improved performance relative totheir predecessors. This would represent enormous benefit in relation to prevented fatalities, decreased
injury occurrence and severity, in addition to decreased economic impact. To better understand the benefits© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

and limitations of current AEB system design, it is essential that system performance be characterized andtested against common scenarios encountered in naturalistic environments.
II. BACKGROUND
The concept of an automatic braking system was first explored in the 1950s with the technology featured on
the 1959 Cadillac Cyclone. While this vehicle was only a concept and not suitable for mass production, theidea of an automatic collision avoidance system was the precursor to AEB systems available today.
Resulting from the discovery of civilian applications for radar technology and continued refinement in theensuing decades, the first production system was introduced on the fourth-generation Honda Inspire with the
Collision Mitigation Braking System. Other manufacturers quickly released their own versions of AEB inparallel to other types of advanced driver assistance systems (ADAS). A detailed narrative of hardware andsoftware design considerations in the context of ADAS is outside the scope of this work; for a general
overview, refer to Section 2.2 of the Active Driving Assistance research report on the AAA NewsRoom.
As previously described, 2010–2015 model year AEB systems have demonstrated measurable benefit interms of reducing the occurrence of police-reported rear-end crashes and resulting fatalities, personal injury,
and property damage. Regarding ADAS in totality, AEB systems are among the most effective at preventing
or mitigating crashes of varying severity. Compared to a 50 percent reduction in total police-reported rearend crashes for vehicles equipped with AEB, vehicles equipped with lane departure warning systems
exhibited an 11 percent decrease in single-vehicle, sideswipe, and head-on crashes relative to equivalent
vehicles without the technology [3].
To understand the performance of current AEB systems within the scope of common crash scenarios that
may be reasonably prevented or mitigated by the technology, AAA selected four common vehicles that were
equipped with an AEB system as standard equipment for evaluation. Data from NHTSA’s Crash Report
Sampling System (CRSS) and Fatality Analysis Reporting System (FARS) were utilized to inform the designof closed-course test scenarios. CRSS obtains its data from a nationally representative probability sample ofpolice-reported crashes involving all types of motor vehicles, pedestrians, and cyclists, ranging from propertydamage-only crashes to those that result in fatalities [4]. In contrast, FARS is a nationwide census providing
yearly data regarding fatal injuries suffered in motor vehicle traffic crashes [5].
The AAA Foundation for Traffic Safety analyzed 2016–2020 CRSS and FARS data involving crashes that
could be reasonably prevented or mitigated by an AEB system. To meet this objective, crashes wererequired to meet all of the following criteria to be included within analysis:







Involved vehicles were passenger vehicles (e.g. car, light pickup truck, SUV, crossover, vans)
The first impact of the striking vehicle was with another stationary or moving passenger vehicle
Exactly two passenger vehicles were involved in the first impact
Striking vehicle was tracking (no traction loss) prior to first impact
Striking vehicle was on the roadway prior to first impact
Striking vehicle did not leave and return to the roadway prior to first impact

Injury estimates and fatalities for included crashes with respect to type, speed limit, and lighting condition areprovided in Tables 1–6. It is important to note that injury and fatality statistics provided herein do not accountfor crashes outside of the specified analysis criteria.

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Total Injuries in Police-Reported Crashes Involving 2 Light-Duty Vehicles, by Crash Type, United States,2016 - 2020. Numbers and percents are statistical estimates derived from a weighted sample of police
reports.
Crash Type
Number of Injuries% of Total Injuries
Rear End
2,405,763
35.6%
T-Bone1,735,167
25.7%
Turn Across Path - Opposite Direction
1,179,053
17.5%
Angle/Sideswipe
458,616
6.8%
Turn Into Path
256,886
3.8%
Head-On
139,171
2.1%
Turn Across Path - Same Direction
91,4001.4%
Turn Opposite Direction Head-On/Sideswipe
28,180
0.4%
Other/Unknown
463,687
6.9%
Total
6,757,924
100%
Data: Crash Report Sampling System (National Highway Traffic Safety Administration). Analysis by AAA
Foundation for Traffic Safety.

Table 1: Total injuries with respect to crash type Source: AAA≤25
Crash Type

Speed Limit (MPH) Applicable to Striking Vehicle
30-35
40-45
50-55
60+
N/A* Unknown
Row Percent
22.4%
33.6%
13.2%
12.2%
0.2%
13.8%
27.8%
26.2%
10.5%
1.4%
2.6%
15.7%
29.3%
45.4%
8.8%
0.9%
0.3%
10.5%
21.1%
26.9%
14.1%
18.7%
0.2%
13.2%
24.0%
29.0%
5.8%
1.3%
7.1%
19.4%
27.1%
27.7%
20.7%
3.1%
0.0%
11.1%
33.1%
26.6%
15.9%
1.6%
0.6%
11.2%
22.8%
20.3%
9.2%
0.4%
2.7%
23.5%
21.2%
27.1%
10.0%
5.9%
3.3%
22.1%
25.1%
32.4%
11.4%
6.7%
1.3%
14.4%

Total

Rear End
4.7%
100.0%
T-Bone15.9%
100.0%
Turn Across Path - Opposite Direction
4.7%
100.0%
Angle/Sideswipe
5.8%
100.0%
Turn Into Path
13.4%
100.0%
Head-On
10.3%
100.0%
Turn Across Path - Same Direction
11.0%
100.0%
Turn Opposite Direction Head-On/Sideswipe
21.2%
100.0%
Other/Unknown
10.4%
100.0%
Total
8.6%
100.0%* N/A denotes No Statutory Limit
Data: Crash Report Sampling System (National Highway Traffic Safety Administration). Analysis by AAA Foundation for Traffic
Safety.

Table 2: Percent distribution of injuries with respect to speed limit Source: AAA
Lighting Conditions
Dark,
Dark,
Dark,
Dawn/
Other/
Daylight Lighted Not Lighted Unknown if Lighted Dusk Unknown
Crash TypeRow Percent
Rear End
75.7%
14.7%
5.0%
0.4%
3.1%
1.1%
T-Bone
75.5%
15.8%
4.2%
0.4%
3.8%
0.3%
Turn Across Path - Opposite Direction
66.7%
24.1%
4.7%
0.5%
3.9%
0.3%
Angle/Sideswipe
67.8%
17.4%
9.6%
0.9%
3.5%
0.8%
Turn Into Path
72.1%
18.6%
4.7%
0.3%
3.9%
0.5%
Head-On
62.0%
16.3%
17.0%
1.3%
3.2%
0.3%
Turn Across Path - Same Direction
76.2%
16.1%
3.6%
0.1%
3.8%
0.2%
Turn Opposite Direction Head-On/Sideswipe
74.3%
16.5%
5.6%
0.0%
3.5%
0.1%
Other/Unknown
66.4%
21.2%
6.5%
0.6%
3.6%
1.7%

Total
100.0%
100.0%
100.0%
100.0%
100.0%
100.0%
100.0%
100.0%
100.0%

Total
72.5%
17.5%
5.4%
0.5%
3.5%
0.7% 100.0%
Data: Crash Report Sampling System (National Highway Traffic Safety Administration). Analysis by AAA Foundation for Traffic Safety.

Table 3: Percent distribution of injuries with respect to lighting condition Source: AAA

In aggregate, the following three crash types are responsible for 79 percent of injuries among analyzed
crashes:© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Rear-end crashes
T-Bone (90° incident angle) crashes
Crashes involving one vehicle turning across the path of an oncoming striking vehicle

Among these crash types involving injury, 60 percent occur on roadways with speed limits of 30-45 mph.
AEB performance evaluations have historically focused on lower testing speeds that do not align with posted
speed limits at which these incidents commonly occur. AAA strongly advocates for system testing thatreasonably accounts for rear-world crash scenarios, rather than exclusively designing test standards around
known system capabilities. Lighting condition is another significant consideration for representative systemevaluation. Among injury-causing crash types previously identified, 74 percent occur in daylight conditions.
Total Fatalities in Police-Reported Crashes Involving 2 Light-Duty Vehicles, by Crash Type, United States,2016 - 2020.
Crash Type
Number of Fatalities% of Total Fatalities
Head-On
7,551
28.5%
T-Bone7,431
28.0%
Other/Unknown
3,186
12.0%
Turn Across Path - Opposite Direction
2,982
11.2%
Angle/Sideswipe
2,650
10.0%
Rear End
2,219
8.4%
Turn Into Path
314
1.2%
Turn Across Path - Same Direction
153
0.6%
Turn Opposite Direction Head-On/Sideswipe
34
0.1%
Total
26,520100%
Data: Fatality Analysis Reporting System (National Highway Traffic Safety Administration). Analysis by
AAA Foundation for Traffic Safety.

Table 4: Total fatalities with respect to crash type Source: AAA≤25
Crash Type

Speed Limit (MPH) Applicable to Striking Vehicle
30-35
40-45
50-55
60+
N/A* Unknown
Row Percent
9%
22%
51%
17%
0%
1%
18%
25%
34%
10%
1%
6%
16%
44%
27%
9%
0%
3%
10%
18%
38%
32%
0%
1%
8%
18%
27%
45%
0%
1%
22%
26%
26%
10%
3%
7%
20%
24%
35%
16%
0%
1%
18%
38%
24%
3%
3%
6%
8%
14%
26%
48%
0%
2%
12%
24%
37%
22%
0%
3%

Total

Head-On
1%
100%
T-Bone6%100%Turn Across Path - Opposite Direction
2%
100%
Angle/Sideswipe
1%100%
Rear End
1%
100%
Turn Into Path
7%
100%
Turn Across Path - Same Direction
5%100%Turn Opposite Direction Head-On/Sideswipe
9%100%
Other/Unknown
2%
100%
Total
3%
100%
* N/A denotes No Statutory Limit
Data: Fatality Analysis Reporting System (National Highway Traffic Safety Administration). Analysis by AAA Foundation for Traffic
Safety.

Table 5: Percent distribution of fatalities with respect to speed limit Source: AAA© 2022 American Automobile Association, Inc.

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Lighting Conditions
Dark,
Dark,
Dark,
Dawn/
Other/
Daylight Lighted Not Lighted Unknown if Lighted Dusk Unknown Total
Crash TypeRow Percent
Head-On
56%
7%
30%
1%
6%
0%
100%
T-Bone
67%
17%
12%
0%
4%
0%
100%
Turn Across Path - Opposite Direction
65%
22%
8%
0%
5%
0%
100%
Angle/Sideswipe
56%
13%
26%
1%
5%
0%
100%
Rear End
45%
23%
28%
1%
3%
0%
100%
Turn Into Path
60%
27%
8%
0%
4%
0%
100%
Turn Across Path - Same Direction
62%
19%
16%
0%
3%
0%
100%
Turn Opposite Direction Head-On/Sideswipe
59%
18%
21%
0%
3%
0%
100%
Other/Unknown
35%
23%
38%
1%
4%
0%
100%
Total
72%
17%
5%
0%
4%
1%
100%
Data: Fatality Analysis Reporting System (National Highway Traffic Safety Administration). Analysis by AAA Foundation for Traffic
Safety.

Table 6: Percent distribution of fatalities with respect to lighting condition Source: AAA

Between 2016 and 2020, there were a total of 187,293 fatalities on public roadways throughout the UnitedStates. Of those fatalities, 99,738 were in single-vehicle crashes and 19,980 were in crashes involving morethan two vehicles. For the remaining 67,575 fatalities in two-vehicle crashes, 29,799 fatalities involved
vehicles other than passenger vehicles (e.g. car, light pickup truck, SUV, crossover, vans). An additional
11,256 fatalities were excluded based on analysis criteria previously identified.
In aggregate, the three crash types responsible for the majority of injuries additionally accounted for 48
percent of the 26,520 fatalities analyzed. As shown in Table 4, head-on type crashes account for over 28
percent of fatal crashes analyzed. AAA previously evaluated a partial head-on crash scenario with three
2020–2021 model year vehicles equipped with an AEB system; no alerts or braking intervention were noted
for any test runs for two of three test vehicles. Due to equipment design limitations and the potential forsignificant vehicle damage, an artificially low closing speed of 40 mph was evaluated. It is unlikely thatcurrent AEB systems will significantly mitigate collisions at speeds where fatalities commonly occur; 90
percent of these fatalities occur on roadways with speed limits at or above 40 mph (potential closing speeds
at or above 80 mph). For detailed methodology and test results, refer to the Active Driving Assistance
System Performance research report on the AAA NewsRoom.
Besides head-on crashes, T-bone and turn across path – opposite direction crashes are responsible for 39
percent of analyzed fatalities, in aggregate. Angle/sideswipe and rear-end crashes account for 10 and 8
percent of analyzed fatalities, respectively. However, rear-end crashes are responsible for over five times
more injuries than angle/sideswipe crashes as shown in Table 1. Based on this observation, AAA
researchers elected to focus on rear-end crashes due to injury prevalence in addition to comparable fatality
rates between the two crash types.
Among fatalities associated with rear-end, T-bone, and turn across path crash types, 76 percent occurred on
roadways with speed limits of 40 mph or greater. Additionally, 63 percent of total fatalities among these crashtypes occur in daylight conditions.
Based on injury and fatality characteristics elucidated from 2016–2020 crash data, closed-course test
scenarios based on intersection and rear-end crashes are of primary focus within this work. AEB systems
have the potential to mitigate or prevent a significant number of these types of injury-causing crashes.
Specifically, the following three closed-course test scenarios will be evaluated in daylight conditions to© 2022 American Automobile Association, Inc.

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understand the performance of current AEB systems in the context of situations during which injuries andfatalities commonly occur:

Test vehicle approaching a stationary target vehicle with no lateral offset between vehicles
Test and target vehicles simultaneously approaching an intersection with an incident angle of 90°
Test vehicle turns left into approaching target vehicle

Detailed test methodology is provided in Section VI and Section VII.
III. VEHICLE SELECTION METHODOLOGY
AAA researchers utilized industry sources and information from owner’s manuals to verify test vehicles were
equipped with an AEB system as standard equipment on all trim levels. Passive warning systems that do not
actively apply braking force in response to a potential collision are not considered within this research. Sales
data were utilized to identify popular vehicles in terms of 2020–2022 model year vehicles in operation (VIO).
The most popular vehicle was selected first; the remaining three test vehicles were selected in sequential
order based on the following criteria:A variety of domestic and import automakers must be represented (no more than one vehicle per
manufacturer group, e.g. Buick/Chevrolet will be included)
A variety of AEB system sensor suppliers will be included (e.g. Continental, Hella, Bosch)
The vehicle model was not previously included in 2021 ADA research conducted by AAA

Based on the preceding requirements, the following vehicles were selected for testing:

2022 Chevrolet Equinox LT with “Chevy Safety Assist”
2022 Ford Explorer XLT with “Pre-Collison Assist with Automatic Emergency Braking”
2022 Honda CR-V Touring with “Honda Sensing®”
2022 Toyota RAV4 LE with “Toyota Safety Sense™”
IV. TEST EQUIPMENT AND RESOURCES

A.

Vehicle Dynamics Equipment1.

Oxford Technical Solutions (OxTS) RT3000 V2 with RT-Range Hunter

Each vehicle was outfitted with an OxTS RT3000 v2 with an RT-Range Hunter. These instruments were
utilized to capture test and target vehicle kinematic information and process vehicle-to-vehicle measurements
relative to the vehicle under test. The RT3000 units interfaced with a site-installed base station to incorporate
real-time kinematics (RTK) technology. The RT-Range interfaced with targets via XLAN. All measurements
were captured at a rate of 100 Hz.

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Figure 1: OxTS RT3000 specifications Source: AAA

Figure 2: OxTS RT-Range Hunter specifications Source: AAA
2.

Futek LAU220 Pedal Force Sensor

Each vehicle was equipped with a brake pedal force sensor to verify no braking intervention was applied
during closed-course testing.

Rated Output (RO)Nonlinearity
Hysteresis
Nonrepeatability
Off Center Loading

2mV/V± 0.25% of RO± 0.25% of RO± 0.10% of RO± 1% or better @Figure 3: Futek LAU220 specifications Source: AAA
3.

DEWESoft CAM-120 Cameras with CAM-BOX2 Distribution Box

Each vehicle was equipped with one camera facing the instrument cluster to capture any visual AEB alerts.
Additionally, one camera was mounted to each side of the vehicle to monitor positioning relative to lanemarkers. Video from all cameras was captured at a rate of 45 Hz.

Image Sensor
Sensor TypeFPS
Dynamic Range
Shutter TimeSony ICX618
CCD
120 FPS @ 640x480
32 dB autogain function
58 ns-60 s (autoshutter function)

Figure 4: DEWESoft CAM-120 specifications Source: AAA© 2022 American Automobile Association, Inc.

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4.

DEWESoft CAN-2 Interface

Test vehicles were equipped with a CAN interface to capture data from OxTS instrumentation. Vehicle
kinematics and range data were captured at a rate of 100 Hz and time-synced with pedal force
measurements and video.
5.

Data Logging Equipment

Test vehicles were either equipped with a DEWESoft DEWE-43 or SIRIUS® slice data logger to log pedal
force measurements at a rate of 2000 Hz. Each data logger was equipped with anti-aliasing filters toattenuate frequencies above the Nyquist frequency.
6.

DRI Low Profile Robotic Vehicle (LPRV) with DRI Soft Car 360®

The robotic vehicle is a hardened, satellite guided, self-propelled, low-profile vehicle, which serves as adynamic platform for the DRI Soft Car. The LPRV has a top speed of 50 mph and a maximum deceleration
rate of 0.8 G. The positions of the vehicle under test and LPRV are measured continually using differential
GPS with RTK correction. Kinematic data relating to the vehicle under test is broadcast to the LPRV via
wireless LAN. This information, in conjunction with pre-loaded time-space trajectories (one each for thevehicle under test and LPRV), allows the LPRV to arrive at predefined locations relative to the vehicle under
test in a repeatable manner.
Additionally, data from the LPRV was processed by the OxTS RT-Range Hunter to calculate LRPV
kinematics relative to the vehicle under test (vehicle under test acts as a non-Newtonian reference frame).

Longitudinal Acceleration
Lateral Acceleration
Path Following Accuracy
Position Measurement Accuracy+0.11 G, -0.8 G± 0.8 G
0.05 m
0.02 mFigure 5: DRI Low Profile Robotic Vehicle specifications Source: AAA© 2022 American Automobile Association, Inc.

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DRI Low Profile Robotic Vehicle Image Source: AAA

The Soft Car 360® is calibrated to be representative of a small passenger vehicle relevant to automotive
sensors including radar and cameras. The hatchback model was utilized for testing; its length, width andheight are 158 in, 67 in, and 56 in, respectively.
B.

Test Facility

All closed-course testing was conducted on roadways specifically designed for standardized ADAS testing on
the grounds of Minter Field Airport in Shafter, California.
All testing was conducted on a dry asphalt surface free of visible moisture. The surface was straight and flat,
free of potholes and other irregularities that could cause significant variations in the trajectory of the test
vehicle.
For rear-end AEB test scenarios, the testing lane was approximately 0.7 miles long and consisted of a twolane roadway divided down the middle by a dashed yellow line. The width and length of each dashed yellow
line segment was 4 inches and 10 feet 4 inches, respectively. The separation distance between line
segments was 29 feet; this distance remained constant throughout the test lane.

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Figure 6: Illustration of testing surface for rear-end AEB test scenarios Source: AAA

Each individual lane was marked by a solid white line on the lateral side and the previously described dashedyellow line on the medial side with a nominal lane width of 12 feet. This lane width is representative of typicalroadways including interstates and limited-access expressways in both urban and rural areas within the
United States.
For intersection-based test scenarios, an intersection specifically designed for ADAS evaluation was utilized.
There were no obstructions present that could impede visibility of vehicles approaching the intersection. The
testing lane was approximately 0.7 miles long and consisted of a two-lane roadway divided down the middle
by a dashed yellow line. The width and length of each dashed yellow line segment was 4 inches and 10 feet
4 inches, respectively. The separation distance between line segments was 29 feet; this distance remained
constant throughout the test lane. Each individual lane was marked by a solid white line on the lateral sideand the previously described dashed yellow line on the medial side with a nominal lane width of 12 feet. Two
identical roadways with width and lane marking dimensions intersected at 90° to form the intersection utilized
for testing; a graphical illustration is provided within Figure 7 (not to scale).

Figure 7: Illustration of testing surface for intersection-based AEB test scenarios Source: AAA© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

V. VEHICLE PREPARATION
All vehicles were procured directly from manufacturers or specialty rental fleets. Vehicles provided by the
manufacturer were verified by the OEM to be suitable for testing. To ensure the proper functioning of the
AEB system, all test vehicles were serviced at Los Angeles–area dealerships to include a four-wheelalignment and if necessary, recalibration of the AEB system before commencing closed-course testing. Eachdealership provided documentation to ensure AEB systems were calibrated according to manufacturer
specifications and updated to the latest software version (as of May 2022).
AEB systems were verified to be enabled and free of modifications. The odometer reading of all test vehicles
was between 200 and 3,700 miles at the start of testing.
Additionally, vehicles were inspected to verify testing suitability according to the following checklist:






No warning lights illuminatedAll system components free of damage and unaffected by any technical service bulletins and/or
recalls
Any stored diagnostic trouble codes were resolved and cleared
All fluid reservoirs filled to at least the minimum indicated levels
Tires inflated to placard pressure following stabilization at ambient temperature in a shaded
environment

Before the start of each testing day, the areas surrounding the image sensors on all test vehicles werecleaned to ensure optimal system operation. A calibration drive of varying speeds was performed prior to
testing for each key cycle. All instrumentation was powered via dedicated 12V batteries and completely
isolated from the vehicle electrical system.
The unloaded curb weight of all vehicles (with a full tank of gas) was measured; this weight was utilized toderive the test weight for each vehicle to include the test driver, instrumentation operator, all instrumentation
and additional ballast weight (if necessary) according to Sections 7.4.5 and 7.4.6 of the Euro NCAP AEB
C2C Test Protocol v.3.0.3 [6]. Unloaded and tested vehicle weights and axle distributions are provided inTables 7 and 8. Test weights were verified prior to the start of testing; the fuel tank was kept at least threequarters full throughout the entirety of testing.
Test Vehicle
Unloaded Weight (lbs) Test Weight (lbs) Weight Difference
Chevrolet Equinox
3312
3754
442
Ford Explorer
4236
4719
483
Honda CR-V
3542
4019
477
Toyota RAV4
3355
3822
467

Table 7: Unloaded and tested vehicle weight Source: AAA
Unloaded Weight (lbs) Test Weight (lbs)
Percent Difference
Test Vehicle
Front Axle Rear Axle Front Axle Rear Axle Front Axle Rear Axle
Chevrolet Equinox
1933
1379
2062
1692
-3.4%
3.4%
Ford Explorer
2146
2090
2290
2429
-2.1%
2.1%
Honda CR-V
2034
1508
2189
1830
-3.0%
3.0%
Toyota RAV4
1976
1379
2088
1734
-4.3%
4.3%

Table 8: Unloaded and tested vehicle weight distribution Source: AAA© 2022 American Automobile Association, Inc.

16

Evaluation of Automatic Emergency Braking Systems

VI. INQUIRY 1: HOW DO COMMON AEB SYSTEMS PERFORM WHEN ENCOUNTERING A
STATIONARY VEHICLE AHEAD?
A.

Objective

Evaluate the performance of common AEB systems in the context of situations involving a potential collision
with a stationary passenger vehicle ahead.
B.

Methodology

In sections herein, “target vehicle” refers to the simulated stationary vehicle. To allow for full characterizationof AEB system performance, the LPRV previously described in Section IV.A.6 was utilized.
For each of the test scenarios, the following data were collected and utilized to characterize system
performance according to parameters within Table 9:

AEB warning indicators (via video recording)Longitudinal velocity and acceleration for test and target vehicles
Longitudinal and lateral position of target vehicle relative to test vehicle
Calculated time-to-collision (TTC)
Parameter

Unit

Description

Alert DistanceftLongitudinal distance between the front of the test vehicle and rearof the target vehicle when the AEB system first provided an alert

Alert Time-to-Collisions

Time-to-collision associated with the alert distanceBraking DistanceftLongitudinal distance between the front of the test vehicle and rearof the target vehicle when test vehicle deceleration reached 0.15 G

Braking Time-to-Collisions

Time-to-collision associated with the braking distance

Average Deceleration

G

Average deceleration from braking initiation to the end of thebraking event

Maximum Deceleration

G

Maximum deceleration from braking initiation to the end of thebraking event

Impact Speed
Separation Distance

Test vehicle speed at first contact with the target vehicle (if

mph applicable)
ft

Final longitudinal distance between the test vehicle and the target
vehicle at the end of the braking event (if no impact occurred)

Note: The end of the braking event is defined as either the moment of impact between the test vehicle and the target vehicle or the
moment when the test vehicle successfully avoided a collison.

Table 9: Performance parameters for rear AEB scenario Source: AAA

Alert distances are provided at the instant that a notification of a vehicle ahead is visible on the test vehicle’s
instrument cluster. Automatic braking is considered to have occurred once the test vehicle’s longitudinal
deceleration exceeds 0.15 G. For test vehicles with adjustable AEB sensitivity settings, the midpoint setting
was utilized for all test runs. If an even number of settings were available, the next latest setting (i.e. thetiming of the collision warning and/or braking application) relative to the midpoint setting was utilized.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

𝑇𝑇𝐶𝑎 =−𝑣𝑟 − √𝑣𝑟2 − 2𝑎𝑇𝑉 𝑟
𝑎𝑇𝑉

Equation 1: TTC with test vehicle acceleration Source: AAA

Equation 1 provides the TTC equation utilized within the following sections, where 𝑣𝑟 is the test vehicle
velocity, 𝑎𝑇𝑉 is the test vehicle acceleration, and 𝑟 is the longitudinal separation distance.
A rear-end collision scenario with no lateral offset between vehicles is within design capabilities of modern
AEB systems including those evaluated with this research. As described in Section II, a majority of injuriescaused by rear-end collisions occur on roadways with posted speed limits of 30–45 mph. Based on thisfinding, test vehicle speeds of 30 mph and 40 mph were evaluated. While the granularity of the dataprecludes insight into typical closing speeds, a stationary vehicle ahead presents the largest possible speed
differential between involved vehicles.
The lateral centerline of the stationary target vehicle was positioned over the lateral centerline of the testinglane as shown in Figure 6. To initiate a test run, the lead vehicle accelerated to the test speed within thecenter of the test lane; for the run to be valid, the test vehicle was required to maintain the target speed within± 1 mph once the front of the test vehicle was within 600 feet of the rear of the stationary target vehicle.
Steady-state speed was maintained until impact with the target vehicle occurred or the AEB system provided
an alert. If an alert was provided, the test driver immediately removed their foot from the accelerator andprovided no intervention until the test vehicle either successfully avoided a collision or impact with the target
vehicle occurred. After each run, data were reviewed to ensure the test driver did not inadvertently applypressure to the brake pedal until one of these two conditions were met. For each test vehicle, five test runs
for each test speed were performed.
C.

Test Results
1.

30 mph Rear AEB Test Scenario

30 mph Rear-End AEB Test Scenario
Test Vehicle

Provided an
Alert

AppliedBrakes

Impacted
Simulated
VehicleChevrolet Equinox
Ford Explorer
Honda CR-V
Toyota RAV4

5/5
5/5
5/5
5/5

5/5
5/5
5/5
5/5

1/5
0/5
2/5
0/5

Note: The results are presented as the number of occurences out of five total
test runs per vehicle per scenario.

Table 10: High-level performance observations for each test vehicle Source: AAA

All test vehicles provided an alert and initiated braking in response to the stationary target vehicle for each of
the five test runs. Two of four test vehicles successfully avoided an impact for each of the five test runs.
Table 10 provides overall results pertaining to alert, braking, and impact phases.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systemsa)Chevrolet Equinox
Chevrolet Equinox

Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

128.5

2.885

38.7

0.900

0.765

1.025

0.0

0.2

Run 2

130.6

2.894

38.4

0.887

0.780

1.075

0.0

0.2

Run 3

125.7

2.877

38.9

0.934

0.766

1.072

0.0

2.2

Run 4

126.1

2.827

37.1

0.873

0.770

1.037

6.4

0.0

Run 5

123.9

2.867

37.0

0.901

0.790

1.123

0.0

2.2

Average

126.9

2.870

38.0

0.899

0.774

1.067

1.3

1.0

2.4

0.023

0.8

0.020

0.010

0.034

2.6

1.0

Standard Deviation

Table 11: Run level test data for the Chevrolet Equinox Source: AAA

For each of the five test runs, the Chevrolet Equinox detected the target vehicle and initiated braking in
response to the stationary target vehicle. In aggregate, an impact was avoided for four of five test runs. An
impact occurred for the fourth test run; the impact speed was significantly reduced by 23.6 mph or 79 percent
relative to the 30 mph test speed. For two of four test runs characterized by no impact, the test vehicle cameto a stop inside the cumulative positioning resolution of vehicle dynamics instrumentation within test andtarget vehicles.
Alert and braking distances as well as deceleration characteristics were consistent for each of the five test
runs. On average, braking was initiated 38 feet from the rear of the target vehicle, corresponding to an
average TTC of 0.899 seconds. The deceleration rate was abrupt for each of the five test runs with anaverage and maximum deceleration magnitude of 0.774 and 1.067 G, respectively.
b)

Ford Explorer
Ford Explorer

Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A*

N/A*

43.0

1.019

0.816

1.330

0.0

4.9

Run 2

80.8

1.878

45.7

1.084

0.823

1.245

0.0

7.5

Run 3

85.5

1.945

45.2

1.058

0.818

1.221

0.0

6.4

Run 4

75.9

1.817

41.6

1.046

0.828

1.127

0.0

7.3

Run 5

73.1

1.739

44.2

1.074

0.829

1.215

0.0

8.7

Average

78.9

1.845

43.9

1.056

0.823

1.228

0.0

7.0

Standard Deviation

4.7

0.076

1.5

0.023

0.005

0.065

0.0

1.3

Table 1: Run level test data for the Ford Explorer Source: AAA

For each of the five test runs, the Ford Explorer detected the target vehicle and initiated braking in responseto the stationary target vehicle. An issue with the instrument cluster camera for the first test run was
discovered in post-processing which precluded recording of the separation distance associated with thevisual alert. However, the instrument operator noted a visual alert was provided during this test run. In
aggregate, an impact was avoided for each of five test runs. Additionally, final separation distances provided
a buffer between the two vehicles.
Alert and braking distances as well as deceleration characteristics were consistent for each of the five test
runs. On average, braking was initiated 43.9 feet from the rear of the target vehicle, corresponding to an
average TTC of 1.056 seconds. The deceleration rate was abrupt for each of the five test runs with averageand maximum deceleration magnitudes of 0.823 and 1.228 G, respectively.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systemsc)

Honda CR-V
Honda CR-V

Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

94.6

2.143

57.2

1.308

0.654

0.834

0.0

7.7

Run 2

100.4

2.203

56.2

1.251

0.329

0.857

3.3

0.0

Run 3

104.4

2.293

49.0

1.122

0.741

0.918

0.0

6.7

Run 4

96.7

2.201

52.9

1.229

0.274

0.839

2.8

0.0

Run 5

100.3

2.201

49.6

1.140

0.709

0.892

0.0

6.9

Average

99.3

2.208

53.0

1.210

0.541

0.868

1.2

4.3

Standard Deviation

3.4

0.048

3.3

0.070

0.199

0.032

1.5

3.5

Table 2: Run level test data for the Honda CR-V Source: AAA

For each of the five test runs, the Honda CR-V detected the target vehicle and initiated braking in responseto the stationary target vehicle. In aggregate, an impact was avoided for three of five test runs. For theremaining two test runs, the impact speed was significantly reduced by an average of 27 mph or 90 percent
relative to the 30 mph test speed. For both test runs, it was noted that braking was discontinued
approximately 6.5 feet from the rear of the target vehicle, resulting in a minor impact.
Alert and braking distances were consistent for each of the five test runs. On average, braking was initiated
53 feet from the rear of the target vehicle, corresponding to an average TTC of 1.210 seconds. In terms ofdeceleration rate, there is a notable decrease in average and maximum deceleration magnitudes for test runsthat resulted in minor impact vs. test runs that resulted in no impact.
d)Toyota RAV4
Toyota RAV4Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

115.5

2.571

52.5

1.214

0.559

0.920

0.0

7.7

Run 2

112.3

2.568

51.3

1.228

0.517

0.745

0.0

3.7

Run 3

115.8

2.607

51.4

1.205

0.532

0.781

0.0

3.8

Run 4

111.9

2.557

55.0

1.292

0.504

0.750

0.0

3.7

Run 5

111.7

2.558

55.4

1.309

0.499

0.825

0.0

3.7

Average

113.4

2.572

53.1

1.250

0.522

0.804

0.0

4.5

1.8

0.018

1.8

0.043

0.022

0.065

0.0

1.6

Standard Deviation

Table 14: Run level test data for the Toyota RAV4 Source: AAA

For each of the five test runs, the Toyota RAV4 detected the target vehicle and initiated braking in responseto the stationary target vehicle. In aggregate, an impact was avoided for each of five test runs. Additionally,
final separation distances provided a buffer between the two vehicles.
Alert and braking distances, as well as deceleration characteristics, were consistent for each of the five test
runs. On average, braking was initiated 53.1 feet from the rear of the target vehicle, corresponding to an
average TTC of 1.250 seconds. The deceleration rate was abrupt for each of the five test runs with averageand maximum deceleration magnitudes of 0.522 and 0.804 G, respectively.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Figure 8: Average alert distance and associated TTC for each test vehicle Source: AAA

Figure 9: Average braking distance and associated TTC for each test vehicle Source: AAA© 2022 American Automobile Association, Inc.

21

Evaluation of Automatic Emergency Braking Systems

Figure 10: Average separation distance between test and target vehicles Source: AAA

Figures 8–10 illustrate the average alert, braking, and final separation distances for each test vehicle. It isnoted that the relative timing of alerts among test vehicles do not directly correlate to the timing of braking
initiation or final separation distances among test vehicles. Within Figure 10, all test runs including thoseresulting in impact (no separation distance) were included within provided averages.
2.

40 mph Rear AEB Test Scenario

40 mph Rear-End AEB Test Scenario
Test Vehicle

Provided an
Alert

AppliedBrakes

Impacted
Simulated
VehicleChevrolet Equinox
Ford Explorer
Honda CR-V
Toyota RAV4

5/5
5/5
5/5
5/5

5/5
5/5
5/5
5/5

5/5
5/5
3/5
1/5

Note: The results are presented as the number of occurences out of five total
test runs per vehicle per scenario.

Table 15: High-level performance observations for each test vehicle Source: AAA

All test vehicles provided an alert and initiated braking in response to the stationary target vehicle for each of
the five test runs. Each test vehicle impacted the target vehicle during at least one of five test runs; two offour test vehicles impacted the target vehicle during each of the five test runs. Table 15 provides overall
results pertaining to alert, braking, and impact phases.

© 2022 American Automobile Association, Inc.

22

Evaluation of Automatic Emergency Braking Systemsa)Chevrolet Equinox
Chevrolet Equinox

Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

178.5

3.015

52.8

0.920

0.646

1.003

22.3

0.0

Run 2

165.8

2.882

55.5

0.999

0.612

0.978

20.7

0.0

Run 3

175.8

2.971

54.6

0.955

0.601

0.764

23.2

0.0

Run 4

174.5

2.924

54.4

0.943

0.595

0.732

23.8

0.0

Run 5

169.6

2.932

53.6

0.961

0.582

0.882

22.7

0.0

Average

172.8

2.945

54.2

0.956

0.607

0.872

22.5

0.0

4.6

0.045

0.9

0.026

0.022

0.109

1.1

0.0

Standard Deviation

Table 16: Run level test data for the Chevrolet Equinox Source: AAA

For each of the five test runs, the Chevrolet Equinox detected the target vehicle and initiated braking in
response to the stationary target vehicle. In aggregate, an impact occurred for each of the five test runs. On
average, the impact speed was reduced by 17.5 mph or 44 percent relative to the 40-mph test speed. This
speed mitigation was less than the average 23.6 mph or 79 percent speed mitigation noted for 30 mph test
runs characterized by target vehicle impact, suggesting that a closing speed of 40 mph is significantly morechallenging for the AEB system relative to 30 mph.
Alert and braking distances as well as impact speed were consistent for each of the five test runs. On
average, braking was initiated 54.2 feet from the rear of the target vehicle, corresponding to an average TTC
of 0.956 seconds. The deceleration rate was abrupt for each of the five test runs with average and maximum
deceleration magnitudes of 0.604 and 0.872 G, respectively.
b)

Ford Explorer
Ford Explorer

Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

122.0

2.118

60.6

1.065

0.835

1.064

9.3

0.0

Run 2

121.6

2.078

60.1

1.045

0.836

1.090

10.7

0.0

Run 3

110.6

1.962

61.2

1.103

0.851

1.086

3.3

0.0

Run 4

123.6

2.073

64.6

1.097

0.854

1.165

7.3

0.0

Run 5

116.3

1.984

59.9

1.037

0.850

1.085

10.5

0.0

Average

118.9

2.043

61.3

1.069

0.845

1.098

8.2

0.0

4.8

0.060

1.7

0.027

0.008

0.035

2.7

0.0

Standard Deviation

Table 17: Run level test data for the Ford Explorer Source: AAA

For each of the five test runs, the Ford Explorer detected the target vehicle and initiated braking in responseto the stationary target vehicle. In aggregate, an impact occurred for each of the five test runs. On average,
the impact speed was significantly reduced by 31.8 mph or 80 percent relative to the 40-mph test speed.
However, the observation that an impact occurred for each test run suggests that a closing speed of 40 mph
is significantly more challenging for the AEB system relative to 30 mph.
Alert and braking distances were consistent for each of the five test runs. On average, braking was initiated61.3 feet from the rear of the target vehicle, corresponding to an average TTC of 1.069 seconds. The
deceleration rate was abrupt for each of the five test runs with average and maximum deceleration
magnitudes of 0.845 and 1.098 G, respectively.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systemsc)

Honda CR-V
Honda CR-V

Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

142.1

2.371

87.3

1.479

0.694

0.928

0.0

8.8

Run 2

147.2

2.522

83.2

1.450

0.471

0.950

9.8

0.0

Run 3

146.2

2.528

81.1

1.433

0.476

0.898

9.3

0.0

Run 4

137.9

2.421

83.5

1.476

0.470

0.910

9.3

0.0

Run 5

154.2

2.592

86.3

1.467

0.709

0.965

0.0

9.7

Average

145.5

2.487

84.3

1.461

0.564

0.930

5.7

3.7

5.4

0.080

2.2

0.017

0.112

0.025

4.6

4.5

Standard Deviation

Table 18: Run level test data for the Honda CR-V Source: AAA

For each of the five test runs, the Honda CR-V detected the target vehicle and initiated braking in responseto the stationary target vehicle. In aggregate, an impact occurred for three of five test runs. For these test
runs, the impact speed was significantly reduced by 30.5 mph or 76 percent relative to the 40-mph test
speed. For runs characterized by no impact, the final separation distance provided a buffer between the twovehicles.
Alert and braking distances were consistent for each of the five test runs. On average, braking was initiated84.3 feet from the rear of the target vehicle, corresponding to an average TTC of 1.461 seconds. In terms ofdeceleration rate, there is a notable decrease in average and maximum deceleration magnitudes for test runsthat resulted in impact vs. test runs that resulted in no impact.
d)Toyota RAV4
Toyota RAV4Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

154.6

2.627

78.6

1.367

0.621

0.888

0.0

3.3

Run 2

151.9

2.609

78.9

1.388

0.583

0.933

0.0

3.0

Run 3

150.0

2.594

75.8

1.345

0.197

0.917

32.1

0.0

Run 4

149.6

2.566

80.0

1.403

0.587

0.857

0.0

3.3

Run 5

150.9

2.595

80.8

1.421

0.581

0.846

0.0

3.1

Average

151.4

2.598

78.8

1.385

0.514

0.888

6.4

2.5

1.8

0.020

1.7

0.027

0.159

0.033

12.8

1.3

Standard Deviation

Table 19: Run level test data for the Toyota RAV4 Source: AAA

For each of the five test runs, the Toyota RAV4 detected the target vehicle and initiated braking in responseto the stationary target vehicle. In aggregate, an impact occurred for one of five test runs. For this test run,the impact speed was reduced by 7.9 mph or 20 percent relative to the 40-mph test speed, resulting in a
major impact. While impact was avoided for four of five test runs, this largely unmitigated impact with thetarget vehicle suggests a closing speed of 40 mph presents a challenge in terms of consistent AEB system
performance. For test runs characterized by no impact, the final separation distance provided a buffer
between the two vehicles.
Alert and braking distances were consistent for each of the five test runs. On average, braking was initiated78.8 feet from the rear of the target vehicle, corresponding to an average TTC of 1.385 seconds. In terms ofdeceleration rate, there is a notable decrease in average deceleration magnitude for the test run that resulted
in major impact vs. test runs that resulted in no impact.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Figure 11: Average alert distance and associated TTC for each test vehicle Source: AAA

Figure 12: Associated braking distance and associated TTC for each test vehicle Source: AAA© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Figure 13: Average separation distance between test and target vehicles Source: AAA

Figures 11–13 illustrate the average alert, braking, and final separation distances for each test vehicle. It isnoted that the relative timing of alerts among test vehicles do not directly correlate to the timing of braking
initiation or final separation distances among test vehicles. Within Figure 13, all test runs including thoseresulting in impact (no separation distance) were included within provided averages.
D.

Discussion

With a closing speed of 30 mph, all test vehicles consistently detected the stationary target vehicle ahead
and initiated braking for each of the five test runs. In aggregate, 17 of 20 total test runs resulted in no impact
with the target vehicle. For impacts that occurred, the average speed mitigation was 25.8 mph or 86 percent
relative to the 30-mph closing speed. These results are encouraging and suggest that evaluated AEB
systems are capable of consistently avoiding or significantly mitigating rear-end impacts at the lower boundof posted speed limits observed when injuries caused by rear-end collisions commonly occur.
At a 40-mph closing speed, performance observations suggest that evaluated AEB systems are morechallenged to consistently avoid rear-end collisions relative to a closing speed of 30 mph. While all test
vehicles detected the stationary target ahead and initiated braking for each of the five test runs, an impact
occurred for 14 of 20 test runs in aggregate. For impacts that occurred, the average speed mitigation was
24.7 mph or 62 percent relative to the 40-mph closing speed. It is important to note that 59 percent of injuriescaused by rear-end collisions occur on roadways with posted speed limits at or above 40 mph. While collision
avoidance would undoubtedly be ideal, consistent impact speed mitigation as demonstrated by this research
could potentially reduce injury severity and in some cases, occurrence.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

VII. INQUIRY 2: HOW DO COMMON AEB SYSTEMS PERFORM WHEN ENCOUNTERING MOVINGVEHICLES IN COLLISION SCENARIOS INVOLVING AN INTERSECTION?
A.

Objective

Evaluate the performance of common AEB systems in the context of typical intersection-based collision
scenarios frequently resulting in injury.
B.

Methodology

In sections herein, “target vehicle” refers to the simulated dynamic vehicle utilized to create a collision
scenario. To allow for full characterization of AEB system performance, the LPRV previously described in
Section IV.A.6 was utilized.
For each of the test scenarios, the following data were collected and utilized to characterize system
performance according to parameters within Table 20:

AEB warning indicators (via video recording),
Longitudinal and lateral velocity and acceleration for test and target vehicles
Longitudinal and lateral position of target vehicle relative to test vehicle
Calculated time-to-collision (TTC)
Parameter

Unit

Description

Alert Distanceft

Separation distance during which AEB system first provided analert. For perpendicular collision scenario, this is defined as thelongitudinal distance between the front of the test vehicle and left
side of the target vehicle. For turning collision scenario, this isdefined as the resultant distance between the left front corner of
the test vehicle and closest point of the target vehicle.

Alert Time-to-Collisions

Time-to-collision associated with the alert distanceBraking Distanceft

Separation distance between test vehicle and target vehicle whentest vehicle deceleration reached 0.15 G. Separation distances aredefined within "Alert Distance" parameter.

Braking Time-to-Collisions

Time-to-collision associated with the braking distance

Average Deceleration

G

Average deceleration from braking initiation to the end of thebraking event

Maximum Deceleration

G

Maximum deceleration from braking initiation to the end of thebraking event

Impact Speed

Separation Distance

Test vehicle speed at first contact with the target vehicle (if

mph applicable)
ft

Final longitudinal distance between the test vehicle and the target
vehicle at the end of the braking event (if no impact occurred).
Separation distances are defined within "Alert Distance"parameter.

Note: The end of the braking event is defined as either the moment of impact between the test vehicle and the target vehicle or the
moment when the test vehicle successfully avoided a collison.

Table 20: Performance parameters for intersection-based AEB scenarios Source: AAA© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Alert distances are provided at the instant that a notification of a vehicle ahead is visible on the test vehicle’s
instrument cluster. Automatic braking is considered to have occurred once the test vehicle’s resultant
deceleration exceeds 0.15 G. For test vehicles with adjustable AEB sensitivity settings, the midpoint setting
was utilized for all test runs. If an even number of settings were available, the next latest setting (i.e. thetiming of the collision warning and/or braking application) relative to the midpoint setting was utilized.
−𝑣𝑟 − √𝑣𝑟2 − 2𝑎𝑇𝑉 𝑟
𝑇𝑇𝐶𝑎 =
𝑎𝑇𝑉
Equation 2: TTC for perpendicular collision scenario Source: AAA

𝑇𝑇𝐶𝑎 =−𝑣𝑟 − √𝑣𝑟2 − 2𝑎𝑇𝑉 𝑟
𝑎𝑇𝑉

Equation 3: TTC for turning collision scenario Source: AAA

Equation 2 and 3 provide the TTC equations utilized for perpendicular and turning collision scenarios,
respectively. Within Equation 2, 𝑣𝑟 is the longitudinal test vehicle velocity, 𝑎𝑇𝑉 is the longitudinal test vehicle
acceleration, and 𝑟 is the longitudinal separation distance. Within Equation 3, 𝑣𝑟 is the relative longitudinal
test and target vehicle velocity, 𝑎𝑇𝑉 is the relative longitudinal test and target vehicle acceleration, and 𝑟 is
the resultant separation distance.
It is acknowledged that collisions involving vehicles moving in a different direction and situations in which thetest vehicle is actively turning are more challenging for AEB systems relative to rear-end collision scenarios.
However, intersection-based collisions between two vehicles account for a significant number of injuries. As
described within Section II, T-bone and turn across oncoming vehicle path type collisions account for 43
percent of analyzed injuries.
Regardless of challenges inherent to intersection-based collision scenarios, AEB system performance in thecontext of these scenarios should be evaluated; consistent impact speed mitigation or collision prevention
could significantly reduce injury severity and/or occurrence. Additionally, a majority of fatalities associatedwith these collision scenarios occur on roadways with speed limits at or above 40 mph; it is likely that impact
speed mitigation would reduce the occurrence of fatalities associated with these collision scenarios.
1.

Perpendicular (T-bone) collision scenario

For each test vehicle, the intersection previously described within Section IV.B was utilized. The lateral
centerline of the target vehicle was oriented above the right lane centerline within a perpendicular roadway
relative to the test vehicle. The lateral centerline of the test vehicle was oriented above the right lane
centerline of the intersecting roadway. This lateral positioning was maintained by both vehicles through theentirety of the test run. Both test and target vehicles approached the intersection at a steady-state test speedof 30 mph. For this collision type, the test speed represents the lower bound of posted speed limits on
roadways where injuries and fatalities commonly occur.

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Evaluation of Automatic Emergency Braking Systems

Figure 14: Perpendicular collision scenario trajectory and impact point Image Source: AAA

To initiate a test run, the test vehicle accelerated to the test speed from a starting point approximately 1000
feet from the potential collision point. For the test run to be valid, the test speed must have been reached andmaintained within ± 1 mph once the front of the test vehicle was within 600 feet of the potential collision point.
At the start of the test run, the front of the target vehicle was located approximately 300 feet from the lateral
centerline of the lane occupied by the test vehicle. The target vehicle accelerated to a steady-state speed of
30 mph automatically in synchronization with the test vehicle. The target vehicle was programmed to adjust
its trajectory such that the front center point of the test vehicle would impact the target vehicle’s left side
center point (50 percent offset relative to the front left corner) if no braking intervention was applied. If the test
vehicle rapidly decelerated before impact, the impact point will be greater than 50 percent offset.
The test vehicle maintained steady-state speed until impact with the target vehicle occurred or the AEB
system provided an alert. If an alert was provided, the test driver immediately removed their foot from theaccelerator and provided no intervention until the test vehicle either successfully avoided a collision or impact
with the target vehicle occurred. After each run, data were reviewed to ensure the test driver did not
inadvertently apply pressure to the brake pedal until one of these two conditions were met. For each test
vehicle, five test runs were performed.
2.

Test vehicle turning left in front of oncoming target vehicle

For each test vehicle, the intersection previously described within Section IV.B was utilized. The lateral
centerline of the target vehicle was oriented above the right lane centerline. The lateral centerline of the test
vehicle was oriented above the centerline of the oncoming lane relative to the target vehicle; this lateralposition was maintained until the left turn was initiated. The test vehicle approached the intersection andinitiated turning at a steady-state speed of 10 mph. The target vehicle approached the intersection at a
steady-state speed of 25 mph.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Figure 15: Turning collision scenario trajectory and impact point Image Source: AAA

It is acknowledged that target and test vehicle speeds are significantly slower relative to posted speed limits
on roadways where injuries and fatalities commonly occur as a result of this collision scenario. However,testing constraints relating to potential vehicle damage, test repeatability, and limitations of evaluated AEB
systems necessitate a slower testing speed.
At the start of the test run, the front of the target vehicle was located approximately 400 feet from thepotential collision point in the middle of the intersection. The target vehicle accelerated to a steady-state
speed of 25 mph automatically in synchronization with the test vehicle. The target vehicle was programmed
to adjust its longitudinal velocity such that the front center point of the test vehicle would impact the target
vehicle’s front left corner if no braking intervention was applied.
To initiate a test run, the test vehicle accelerated to the test speed from a starting point approximately 600
feet from the potential collision point; the left turn signal was engaged throughout the test run. For the test run
to be valid, the test speed must have been reached and maintained within ± 1 mph once the test driverinitiated the left turn. For consistency between test runs, a traffic cone approximately 6 feet to the right of the
roadway edge was utilized to signal the driver to begin turning; chalk was used to mark the turning radius
followed by the test driver.
The test vehicle maintained steady-state speed throughout the turn until impact with the target vehicle
occurred or the AEB system provided an alert. If an alert was provided, the test driver immediately removed
their foot from the accelerator and provided no intervention until the test vehicle either successfully avoided acollision or impact with the target vehicle occurred. After each run, data were reviewed to ensure the test
driver did not inadvertently apply pressure to the brake pedal until one of these two conditions were met. For
each test vehicle, five test runs were performed.

© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

C.

Test Results
1.

Perpendicular (T-bone) collision scenario

30 mph Perpendicular AEB Test Scenario
Test Vehicle

Provided an
Alert

AppliedBrakes

Impacted
Simulated
VehicleChevrolet Equinox
Ford Explorer
Honda CR-V
Toyota RAV4

0/5
0/5
0/5
0/5

0/5
0/5
0/5
0/5

5/5
5/5
5/5
5/5

Note: The results are presented as the number of occurences out of five total
test runs per vehicle per scenario.

Table 21: High-level performance observations for each test vehicle Source: AAA

All test vehicles failed to detect the imminent perpendicular collision with the target vehicle resulting inunmitigated impact for each of the five test runs. Table 21 provides overall results pertaining to alert, braking,and impact phases. Tables 22–25 provide run-level data for each test vehicle; impact speed is the only
reported parameter as neither alerts nor braking mitigation were provided for any test runs.
Chevrolet Equinox
Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

30.2

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

30.0

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

30.3

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

30.2

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

29.4

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

30.0

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.3

0.0

Table 22: Run-level test data for the Chevrolet Equinox Source: AAA
Ford Explorer
Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

29.7

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

29.8

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

30.3

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

29.8

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

29.3

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

29.8

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.3

0.0

Table 23: Run-level test data for the Ford Explorer Source: AAA© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Honda CR-V
Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

30.7

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

30.4

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

30.3

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

30.0

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

30.3

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

30.3

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.2

0.0

Table 24: Run-level test data for the Honda CR-V Source: AAA
Toyota RAV4Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

29.5

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

30.8

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

30.1

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

30.8

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

29.8

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

30.2

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.5

0.0

Table 25: Run-level test data for the Toyota RAV4 Source: AAA
2.

Test vehicle turning in front of oncoming target vehicle

10 mph Turn-In AEB Test Scenario
Test Vehicle

Provided an
Alert

AppliedBrakes

Impacted
Simulated
VehicleChevrolet Equinox
Ford Explorer
Honda CR-V
Toyota RAV4

0/5
0/5
0/5
0/5

0/5
0/5
0/5
0/5

5/5
5/5
5/5
5/5

Note: The results are presented as the number of occurences out of five total
test runs per vehicle per scenario.

Table 26: High-level performance observations for each test vehicle Source: AAA

As the left turn was initiated, all test vehicles failed to detect the imminent collision with the target vehicle
resulting in unmitigated impact for each of the five test runs. Table 26 provides overall results pertaining toalert, braking, and impact phases. Tables 27–30 provide run-level data for each test vehicle; impact speed isthe only reported parameter as neither alerts nor braking mitigation were provided for any test runs.
Chevrolet Equinox
Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

9.9

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

9.8

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

9.7

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

9.7

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

9.8

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

9.8

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.1

0.0

Table 27: Run-level test data for the Chevrolet Equinox Source: AAA© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

Ford Explorer
Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

10.3

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

9.7

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

10.2

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

9.7

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

10.0

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

10.0

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.2

0.0

Table 28: Run-level test data for the Ford Explorer Source: AAA
Honda CR-V
Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

10.6

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

9.6

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

10.2

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

10.0

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

9.7

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

10.0

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.4

0.0

Table 29: Run-level test data for the Honda CR-V Source: AAA
Toyota RAV4Alert Distance (ft)

Alert TTC (s)Braking Distance (ft) Braking TTC (s) Avg Deceleration (G) Max Deceleration (G) Impact Speed (mph) Separation Distance (ft)

Run 1

N/A

N/A

N/A

N/A

N/A

N/A

10.1

0.0

Run 2

N/A

N/A

N/A

N/A

N/A

N/A

10.2

0.0

Run 3

N/A

N/A

N/A

N/A

N/A

N/A

10.2

0.0

Run 4

N/A

N/A

N/A

N/A

N/A

N/A

10.7

0.0

Run 5

N/A

N/A

N/A

N/A

N/A

N/A

10.5

0.0

Average

N/A

N/A

N/A

N/A

N/A

N/A

10.3

0.0

Standard Deviation

N/A

N/A

N/A

N/A

N/A

N/A

0.2

0.0

Table 30: Run-level test data for the Toyota RAV4 Source: AAA

D.

Discussion

Each evaluated AEB system failed to issue an alert or provide any braking mitigation for any of the five test
runs for each test scenario. In aggregate, 40 of 40 test runs involving common intersection-based scenarios
resulted in impact with no speed mitigation. This finding illustrates the reality that current AEB systems are
ineffective at mitigating or preventing intersection-based collision scenarios, which accounted for 2,914,220
police-reported injuries and 10,413 fatalities in the United States between 2016 and 2020. It is additionally
important to note that evaluated test speeds were representative of the lower bound of posted speed limits
observed when injuries and fatalities caused by intersection-based collisions typically occur.
VIII. CONCLUSIONS
In general, evaluated AEB systems were effective in consistently avoiding or mitigating rear-end collisions
with a stationary vehicle ahead at speeds of 30 and 40 mph. This finding is encouraging due to theassociated potential of AEB systems to reduce injuries and fatalities caused by this common collision
scenario. As the collective vehicle fleet continues turnover with the introduction of more vehicles equipped© 2022 American Automobile Association, Inc.

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Evaluation of Automatic Emergency Braking Systems

with AEB, it is anticipated that injury occurrence and severity as well as fatalities associated with rear-end
collisions will gradually decrease over time.
For common intersection-based collision scenarios included within this work, all evaluated AEB systems
were ineffective at providing an alert or braking mitigation. Specifically, 100 percent of test runs involving anintersection-based collision scenario (T-bone and turn across path–opposite direction) resulted in an impact
with no speed mitigation. While system performance results could be viewed as discouraging, it is important
to note that standardized testing by research and regulatory agencies focus on front-to-rear collisions (i.e.,
rear-end collision scenarios). Performance observations within this work highlight an opportunity for further
system refinement in the context of challenging collision scenarios. AAA recommends that automakers andtechnology companies continue to invest in ADAS development for scenarios that can offer the greatest
safety benefit. As the industry continues down the path of driving automation, continual enhancement of
established ADAS in the interim will help save lives, reduce the occurrence of serious injury, and promote
public acceptance of future iterations of vehicle automation.
IX. KEY FINDINGS
1. How do evaluated AEB systems perform when encountering a stationary vehicle ahead?
a. At a steady-state approach speed of 30 mph, evaluated AEB systems prevented a collision for 17
of 20 test runs, in aggregate. For test runs that resulted in a collision, the impact speed was
reduced by an average of 86 percent.
b. At a steady-state approach speed of 40 mph, evaluated AEB systems prevented a collision for 6of 20 test runs, in aggregate. For test runs that resulted in a collision, the impact speed was
reduced by an average of 62 percent.
2. How do evaluated AEB systems perform when encountering moving vehicles in collision scenarios
involving an intersection?
a. For a perpendicular collision scenario, an unmitigated collision occurred for 100 percent of test
runs, in aggregate.
b. For a collision scenario involving a left turn in front of an oncoming vehicle, an unmitigatedcollision occurred for 100 percent of test runs, in aggregate.
X. RECOMMENDATIONS
1. Automakers should continue to refine AEB systems with the objective of incorporating collision mitigation
capability for common intersection-based crash scenarios.
2. Automakers and regulatory agencies should prioritize focus on system design and test protocols aroundcollision attributes observed when injuries and fatalities commonly occur.
3. Regardless of current system limitations, automakers should continue efforts to include AEB systems as
standard equipment throughout their product portfolio.

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XI. REFERENCES[1] NHTSA, "U.S. DOT and IIHS announce historic commitment of 20 automakers to make automatic
emergency braking standard on new vehicles," 17 March 2016. [Online]. Available:
https://www.nhtsa.gov/press-releases/us-dot-and-iihs-announce-historic-commitment-20-automakersmake-automatic-emergency. [Accessed 23 June 2022].
[2] IIHS-HLDI, "IIHS eyes higher-speed test for automatic emergency braking," 5 May 2022. [Online].
Available: https://www.iihs.org/news/detail/iihs-eyes-higher-speed-test-for-automatic-emergency-braking.
[Accessed 23 June 2022].
[3] Insurance Institute of Highway Safety, "Real-world benefits of crash avoidance technologies," March
2022. [Online]. Available: https://www.iihs.org/media/290e24fd-a8ab-4f07-9d92737b909a4b5e/4GauQQ/Topics/ADVANCED%20DRIVER%20ASSISTANCE/IIHS-HLDI-CA-benefits.pdf.
[Accessed 28 June 2022].
[4] NHTSA, "Crash Report Sampling System," [Online]. Available: https://www.nhtsa.gov/crash-datasystems/crash-report-sampling-system. [Accessed 28 June 2022].
[5] NHTSA, "Fatality Analysis Reporting System," [Online]. Available: https://www.nhtsa.gov/researchdata/fatality-analysis-reporting-system-fars. [Accessed 28 June 2022].
[6] Euro NCAP, "Test Protocol - AEB Car-to-Car Systems Version 3.0.3," April 2021. [Online]. Available:
https://cdn.euroncap.com/media/62794/euro-ncap-aeb-c2c-test-protocol-v303.pdf.

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