NHTSA Evaluation of the FlexGTR Legform on US Vehicles
Brian Suntay & Ann Mallory
Transportation Research Center Inc.
Jason Stammen
NHTSA Vehicle Research and Test Center
1
This is a work of the U.S. Government and is not subject to copyright in the United States; it may be used or reprinted without permission.
Pedestrian Leg Testing

The Pedestrian Global Technical Regulation (GTR No. 9)
includes a projectile leg simulating a moving vehicle
hitting a stationary pedestrian at 40 km/h
2
Goals of the Testing

Comparison of vehicle performance with TRL
versus Flex-GTR legforms

Confirm whether the Flex-GTR legform is
sensitive enough to distinguish marginally
performing vehicles from poor performing
vehicles

Test the Flex-GTR’s durability against aggressive
locations on US vehicle bumpers
3
Pedestrian Legforms
TRL
Flex-GTR
4
TRL

Rigid Legform Impactor

Steel femur and tibia
segments
◦ Frangible steel ligaments

Instrumentation:
◦ Tibia accelerometer
◦ Rotary pot with rigid arm
5
Flex-GTR

Flexible Legform Impactor
◦ Increased biofidelity

Flexible bone core, wire
ligaments, knee tension
cables

Instrumentation:
◦ Tibia and Femur strain gauges
◦ Ligament string potentiometers
(MCL, ACL, PCL, ACL)
6
Injury Assessment
Bending Injury Measures
Knee Bending Angle
MCL Elongation
Shear Injury Measures
Knee Shear Displacement
ACL/PCL Elongation
Tibia Fracture Measures
Tibia Acceleration
Tibia Bending Moment
TRL
7
Flex-GTR
Volkswagen Passat
Mazda Miata
Honda Civic
Honda Pilot
Chevrolet Silverado
Chevrolet Equinox
Test Results
10
TRL Test Results
Peak Shear Displacement (mm)
Passat
Peak Bending Angle (deg)
Passat
8.1
31.1
Miata
8.9
Miata
Civic
8.9
Civic
33
Pilot
33
Pilot
6.8
Silverado
Silverado
8.3
Equinox
2
4
6
8
10
307
Miata
402
Civic
326
Pilot
401
Silverado
353
Equinox
183
0
100
200
300
400
33.1
0
Peak Tibia Acceleration (g)
Passat
26.5
Equinox
7.5
0
26.5
500
11
5
10
15
20
25
30
35
Flex-GTR Test Results
Peak Tibia 1 Moment (Nm)
Passat
Peak ACL Elongation (mm)
Passat
428
Miata
460
Civic
475
Pilot
100
200
300
400
500
Peak MCL Elongation (mm)
Passat
28.2
Miata
24.1
Civic
27.0
Pilot
32.1
Silverado
22.3
Equinox
34.4
0
10
20
30
40
Peak PCL Elongation (mm)
Passat
7.9
Miata
6.4
Civic
7.2
Pilot
7.1
Silverado
5.6
Equinox
8.4
0
2
4
6
8
Civic
14.8
15.5
7.9
11.9
Equinox
378
0
14.3
Silverado
333
Equinox
Miata
Pilot
402
Silverado
13.9
10
0
5
10
15
20
Comparison of Results
TRL vs Flex-GTR
13
Comparison of Results – TRL vs Flex-GTR
Fracture Measures
Bending Injury Measures
Passat
Passat
Miata
Miata
Civic
Civic
Pilot
Pilot
Silverado
Silverado
Equinox
Equinox
0
50
100
150
Injury Measure as % of Limit
TRL - Tibia Acceleration
200
Flex-GTR - Max Tibia Bend Moment
0
50
100
150
Injury Measure as % of Limit
TRL - Knee Bending Angle
Shear Injury Measures
Passat
Miata
Civic
Pilot
Silverado
Equinox
0
50
100
150
Injury Measure as % of Limit
TRL - Knee Shear Displacement
Flex-GTR - Max ACL/PCL Elongation
200
Flex-GTR - MCL Elongation
200
Comparison of Results – TRL vs Flex-GTR
Bending Injury Measures
200
160
180
140
Civic
120
Equinox
100
80
FlexGTR % of Injury Limit
180
Miata
Passat
Pilot
Silverado
60
40
20
Equinox
160
Pilot
140
Passat
Miata
120
100
Civic
Silverado
80
0
60
40
20
0
0
20 40 60 80 100 120 140 160 180
TRL % of Injury Limit
0 20 40 60 80 100 120 140 160 180200
TRL % of Injury Limit
Shear Injury Measures
160
FlexGTR % of Injury Limit
FlexGTR % of Injury Limit
Fracture Measures
140
Pilot
Passat
120
100
Equinox
Civic
Miata
80
Silverado
60
40
20
0
0
20
40 60 80 100 120 140 160
TRL % of Injury Limit
Summary of Findings

The Flex-GTR measures lower values than the
TRL legform with respect to their current injury
limits
◦ In contrast:
 Matsui et al., Characteristics of the TRL Pedestrian Legform and the Flexible Pedestrian
Legform Impactors in Car-front Impact Tests, Paper Number 09-0206, 21st International
Technical Conference on the Enhanced Safety of Vehicles, 2009.
 Yoon et al., Evaluation of Usefulness and Repeatability for Pedestrian Protection Flex-PLI,
Paper Number 11-0425, 22nd International Technical Conference on the Enhanced Safety of
Vehicles, 2011.

Aggressive vehicle bumper impact locations
chosen
16
Flex-GTR Vehicle Sensitivity
17
Sensitivity

Testing with a previous version of the Flex-GTR legform suggested an inability of the
legform to distinguish among vehicles that performed poorly (Mallory, 2010)
Fracture

Bend
Shear
Results from current series of tests
Fracture Measures
Bending Injury Measures
Shear Injury Measures
Passat
Passat
Passat
Miata
Miata
Miata
Civic
Civic
Civic
Pilot
Pilot
Pilot
Silverado
Silverado
Silverado
Equinox
Equinox
Equinox
0

50
100
150
200
Injury Measure as % of Limit
0
50
100
150
200
Injury Measure as % of Limit
0
50
100
150
200
Injury Measure as % of Limit
Three additional tests performed on the center of the three passenger cars
Volkswagen Passat
Mazda Miata
Honda Civic
Comparison of Old and New Flex-GTR Data – Center Impacts
Bending Injury Measures
Fracture Measures
Passat
Passat
Miata
Miata
Civic
Civic
0
20
40
60
80
100
120
0
140
20
40
60
100
Flex-GTR (New) - MCL Elongation
Flex-GTR (New) - Max Tibia Bend Moment
Flex-GTR (Old) - MCL Elongation
Flex-GTR (Old) - Max Tibia Bend Moment
Shear Injury Measures
Passat
Miata
Civic
0
80
20
40
60
80
100
Flex-GTR (New) - Max ACL/PCL Elongation
Flex-GTR (Old) - Max ACL/PCL Elongation
120
120
140
Summary of Findings

The Flex-GTR measures lower values than the
TRL legform with respect to their current injury
limits

The Flex-GTR seems to be able to distinguish
differences in relatively aggressive vehicle bumper
designs
21
Flex-GTR Durability
22
Observations and Durability Assessment (Flex-GTR)
Misalignment of the knee after
impacts

Femur strain gauge #2
(middle gauge)
◦ Broken gauge/wire
◦ Still being investigated
Tear in the neoprene skin and
scratches on the femur knee block
Summary of Findings

The Flex-GTR measures lower values than the TRL
legform with respect to their current injury limits

The Flex-GTR seems to be able to distinguish
differences in relatively aggressive vehicle bumper
designs

The Flex-GTR was observed to be durable
◦ Survived US vehicle bumper impacts that exceeded injury
limits
◦ A majority of the issues that were observed were minor and
repairable
24
Flex-GTR Repeatability
(Additional Observation)
25
Flex-GTR Repeatability
Injury Measurement
Injury
Reference
Value
(FlexTEG)
Chevrolet Silverado
Impact Location
Center
GTR (1001)
GTR (1002)
%Difference
73.7
77.3
5%
139.5
138.5
1%
Femur 1 (Lower)
252.1
245.6
3%
Tibia 1 (Upper)
332.7
332.6
0%
311.1
319.5
3%
233.5
237.4
2%
110.5
107.9
2%
Femur 3 (Upper)
Femur Moment
Femur 2 (Middle)
(Nm)
Tibia Moment Tibia 2 (Mid Upper)
(Nm)
--*
340 Nm
(380 Nm)
Tibia 3 (Mid Lower)
Tibia 4 (Lower)
MCL Elongation (mm)
22 mm
--
22.3
NA
ACL Elongation (mm)
13 mm
8
7.9
1%
PCL Elongation (mm)
13 mm
5.4
5.6
4%
LCL Elongation (mm)
--*
-4.2
-3.8
10%
Tibia Acceleration (g)
Velocity (m/s)
--*
--*
-59.2
-59.5
1%
11.1
11.1
Average:
0%
3%
26
Summary of Findings

The Flex-GTR measures lower values than the TRL legform
with respect to their current injury limits

The Flex-GTR seems to be able to distinguish differences in
relatively aggressive vehicle bumper designs

The Flex-GTR was observed to be durable

Flex-GTR repeatability was not directly evaluated, but
◦ Survived US vehicle bumper impacts that exceeded injury limits
◦ A majority of the issues that were observed were minor and
repairable
◦ Silverado Flex-GTR tests 1001 and 1002 showed similar values at
the same impact location, which is promising
27
NHTSA Evaluation of the
Flex-GTR Legform on US
Vehicles
Brian Suntay & Ann Mallory
Transportation Research Center Inc.
Jason Stammen
NHTSA Vehicle Research and Test Center
28
This is a work of the U.S. Government and is not subject to copyright in the United States; it may be used or reprinted without permission.