ABSTRACT: Pedestrians account for 18% of Australian
road fatalities. Ways to reduce this toll through improved frontal design
of vehicles have been hampered by a lack of objective tests to simulate
pedestrian impacts. The European Experimental Vehicles Committee therefore
developed a series of tests to assess impacts to the head, upper legs and
lower legs of pedestrians. The European New Car Assessment Program (Euro-NCAP)
incorporated these tests in its crash test program in 1996. During 1999
the Australian New Car Assessment Program aligned its test program with
Euro-NCAP. Pedestrian protection tests of several Australian vehicles recently
commenced at the Road Accident Research Unit of the University of Adelaide.
This paper describes the tests and rating system now used by Australian
NCAP for assessing pedestrian protection.
Disclaimer: This paper represents the view of the authors and not those of any organisation
Updates:
1. Introduction
1.1 Pedestrian Injury Statistics
In the 12 months ending June 1999 there were a total of 324 pedestrian
fatalities and 2784 pedestrians hospitalised in Australia [1]. Pedestrian
fatalities account for 18% of all Australian road fatalities. This compares
with 13% in the USA, 28% in the UK and Japan and 16% averaged across European
nations [2].
Pedestrians struck by the front of a vehicle account for 84% of pedestrian
fatalities and therefore 15% of all road fatalities in Australia. Head
injuries, most of which involved impacts with the vehicle, were the cause
of death in two-thirds of the fatalities [1, 3].
1.2 Regulations and standards
There are no Australian regulations which apply specifically to the
pedestrian 'friendliness' of vehicles. Australian Design Rule 42/ "General
Safety Requirements" refers, in general, to the injury potential of equipment
fitted to vehicles but does not set performance requirements.
In the late 1980s the European Experimental Vehicles Committee (EEVC)
began to develop a set of standards that would minimise serious injury
to pedestrians in impacts up to 40 km/h. In 1991 EEVC proposed a set of
component tests representing the three most important mechanisms of injury:
head, upper legs and lower legs (see Section 2 for further details). This
work was incorporated in the consumer tests conducted by Euro-NCAP with
the first results published in 1997.
Early in 1999 the European Commission (EU) announced that it planned
to introduce regulations to make the EEVC requirements mandatory within
a few years.
1.3 Developments in Australia
Research on the influence of car design on injuries to pedestrians has
been conducted since at least the 1970s [3,4]. Several projects have endeavoured
to investigate the influence of bull bars on pedestrian kinematics and
injuries [5,6].
In the late 1990s the Road Accident Research Unit of the University
of Adelaide developed free-flight headform tests to evaluate the injury
potential of vehicle fronts [7]. This work was supported by the Federal
Office of Road Safety.
Using the new facilities, several designs of bull bar were compared
with the unmodified front of a popular large four-wheel-drive vehicle.
An innovative foam plastic device to protect the vehicle from damage by
wildlife was also tested and compared favourably against metal bull bar
designs [8].
In February 1999 the International Harmonised Research Activities Pedestrian
Safety Working Group met in Adelaide. Research results were presented at
a seminar that followed the meeting [2]. This included detailed discussion
about the EEVC component tests for assessing pedestrian protection.
Also during 1999 the Australian New Car Assessment Program (ANCAP) aligned
its crash test and assessment procedures with those of Euro-NCAP, including
the EEVC pedestrian test protocol. The first ANCAP tests to this protocol
began at the University of Adelaide this year. Results from that test series
should be available in May 2000.
1.4 Overseas Developments
The Japanese NCAP organisation OSA intends to introduce the EEVC pedestrian
tests into its consumer test program.
Honda has developed pedestrian impact simulation software [9] and a
full scale adult dummy (POLAR) for use in impact research [2]. McLean [4]
points out there are several difficulties with the use of full dummy tests
in regulations and standards.
The US National Highway Traffic Safety Administration (NHTSA), which
pioneered consumer crash tests, is looking at the need for pedestrian protection
tests but, apparently, has not yet committed to the EEVC protocol.
Pedestrian protection requirements are being considered in the United
Kingdom [10].
2 Test Procedures
2.1 Test Description
This section provides a general description of the EEVC procedures,
as now used by ANCAP. A more detailed description of the procedures and
test equipment is given in references 11, 12 & 13.
The procedures require determination of locations that are most likely
to be injurious and those that are least likely to be injurious. The vehicle
manufacturer may nominate the latter cases, provided that they are not
too close to locations judged to be injurious.
2.2 Three Sub-system Tests
The EEVC procedures require three sub-system tests that simulate impacts
by the head, upper leg and knee/lower leg. At the Adelaide seminar it was
stressed several times that any assessment must be based on all three tests
because the design of a vehicle simply to meet one of the requirements
could lead to a degradation of protection for another area.
2.3 Lower Leg
This test simulates injuries that a pedestrian may have with the soft
tissue injuries to the knee joint or fractures to the adjacent leg bones.
These happen early in the pedestrian strike.
Figure 1. EEVC Lower Legform Test
The test device simulates the human lower leg, including the knee joint.
The impact occurs side-on to the plane of articulation of the knee. The
angular movement of the knee joint at right angles to the axis of articulation
is measured. Tibia deceleration and knee shear displacement are also measured.
Three impact tests are conducted, one in each of three equal transverse
zones across the vehicle. The impact locations in two of the zones are
chosen for highest injury potential (generally the stiffest structure).
The least harmful location is chosen for the third zone.
Euro-NCAP assigns a red (poor) rating if the tibia acceleration exceeds
230g, the knee shear exceeds 7.5mm or the knee bending angle exceeds 30
degrees.
2.4 Upper Leg Impacts
This simulates impacts that are frequently associated with fractures
to the femur and pelvis. This impact takes place later than the lower leg
impact, and in the test, the impactor representing the upper leg strikes
the leading edge of the bonnet.
Figure 2. EEVC Upper Legform Test
The test device simulates the upper leg with a covering of elastomeric
foam, the equivalent to leg flesh. When it strikes the bonnet leading edge
the leg can rotate around a friction loaded pivot.
The procedures prescribe a minimum impact energy, based on the height
of the bonnet leading edge (BLE) and the forward projection of the bumper
('bumper lead').
Three impact tests are conducted, one in each of three equal transverse
zones across the vehicle. The impact locations in two of the zones are
chosen for highest injury potential (generally the stiffest structure).
The least harmful location is chosen for the third zone.
Bending moments and resultant forces are measured. Euro-NCAP assigns
a red (poor) rating if the bending moment exceeds 400Nm or the resultant
force exceeds 7kN.
2.5 Head Impacts
Typically the head impacts with the bonnet after the lower and upper
leg contact, with the head pitched down onto the bonnet top.
Two headforms are used to simulate this type of head impact: an child
headform with a mass of 2.5 kg and an adult head form with a mass of 4.8
kg. The child headform strikes are to the front of the bonnet (wrap-around
distance 1 to 1.5m ) while the adult headform strikes are to the rear of
the bonnet or beyond (wrap around distance 1.5 to 2.1 m).
Figure 3. EEVC Child Headform Test.
Six tests are conducted with each headform, based on three equal transverse
zones and two impacts within each zone. One impact location is chosen for
highest injury potential, such as above engine parts, suspension mounting
points or bonnet hinges. The other is chosen to be the least injurious.
Where the left and right zones have similar structures judged to be the
most injurious the next worst location is chosen for one of the zones.
If between one third and two thirds of a test zone for the adult headform
test is found to be within the windscreen area then three default scores
are assigned for the windscreen/a-pillar: one poor (a-pillar) and two good
(glass away from dash) giving a score of 4. This is added to the three
scores for impact tests to the bonnet. The impact locations in two of the
bonnet zones are chosen for highest injury potential. The least harmful
location is chosen for the third zone.
If more than two-thirds of the adult headform test zone is within the
windscreen then only one impact test is usually conducted. Five default
scores are assigned: two poor (a-pillars) and three good (glass, away from
dash) giving an adult headform score of 6. This is added to the score for
the single test that is chosen for the highest injury potential in the
centre zone. This is generally located at the lower centre of the windscreen
where the headform is likely to contact the dash through the glass.
Accelerometers in the headform are used to determine Head Injury Criterion
(HIC). Euro-NCAP assigns a red (poor) rating if the test results in a HIC
of 1,500 or more (HIC36 is assumed but the deceleration curve
is typically a spike of less than 8ms duration).
3 Assessment of Test Results
3.1 Injury Measurements
Under the Euro-NCAP Assessment Protocol, each impact is assigned a score
based on the injury measurements. The scoring system is summarised in Table
I. Two injury values are prescribed. The 'good' value earns a maximum of
two points for that impact and a 'poor' value earns zero points. A 'sliding
scale' applies for intermediate points. For example, a HIC of 1300 would
earn ((1500-1300)/(1500-1000)*2 = 0.8 points.
Where more than one injury measurement is taken for an impact the value
with the worst score is used in the analysis.
Table I. Assessment of Pedestrian Impact Tests
A star rating is assigned from the
overall score.
27.5 or more 4 Stars
18.5 to 27.49 3 Stars
9.5 to 18.49 2 Stars
0.5 to 9.49 1 Star
Less than 0.5 Zero Stars
(This list incorporates a rounding process
described in the Euro-NCAP protocol).
3.3 Typical Euro-NCAP scores
Appendix A sets out the results of
an analysis of 14 Euro-NCAP pedestrian assessments. The mean overall scores
of 11.01 for passenger vans and 9.75 for small cars correspond to the low
end of a 2-Star rating. Upper leg scores were particularly poor. 'Default'
adult head scores of 6 or 8 applied to most of the passenger vans - probably
due to their short bonnet lengths.
Of the 12 'family' cars assessed
by Euro-NCAP one was awarded one star and the remainder were awarded 2
stars. In recently released results for 'super-minis' all seven vehicles
were awarded 2 stars. So far no vehicle has earned more than 2 stars.
4 Improvements to Vehicle Design
Changes to the design of vehicle
fronts are discussed in references 4, 8 11, 12 and 14. Lawrence [12] notes
that "...solutions to the problem of achieving better pedestrian safety
are often readily available, low cost and could be applied over a higher
proportion of the car surface". This appears to contradict Clemo [15] from
MIRA: "It appears that cars will need to undergo profound changes in design
to meet the required standard". However, the MIRA research involved existing
vehicle models.
Lawrence makes the point that relatively
simple changes to detail in the early design stages of a new model can
lead to major improvements in pedestrian protection. Several of his tips
are discussed below.
4.1 Front bumper
A deeper profile to support the leg-form
is a possible solution, or to provide a secondary support bar below the
bumper would reduce pitching of the leg-form and bending of the knee joint.
The bumper needs localised compliance
and then efficient energy absorption. Foam plastics are available to achieve
this aim, together with recovery characteristics that minimise damage during
low speed car-to-car collisions. The deformed profile of the vehicle during
the impact needs to be considered. Spoilers and similar low-mounted, compliant
structures can help to reduce the loads on the lower legs.
4.2 Headlamps
As the headlamps change from glass
to plastic the hardness of the headlamp will change significantly, reducing
the possibility of causing severe pedestrian injury. But to maintain good
lamp alignment, the mounting must be stiff and not subject to vibration,
which will require some development to meet the overall requirements.
4.3 Bonnet leading edge
There is scope for reducing the stiffness
of components at the leading edge of the bonnet. Improvements include moving
the location of the bonnet latch rearward, or to the sides and moving transverse
stiffeners back from the leading edge of the bonnet.
Crush depths, under test, of between
65mm and 150mm are appropriate, depending on geometry.
4.4 Bonnet and fender tops
Redesign of the top of fenders and
the fender-bonnet edges that allows room for crush to limit injury is essential.
Head-form contact with the hard seam generally located at the edge of the
panel results in high head impact forces. Use of energy absorbing structures
such as sandwich structure is one possibility.
Improvements include increasing under-bonnet
clearances, locating softer components at the top of the engine and avoiding
localised stiffness of the bonnet in favour of a more distributed structure.
A bonnet which wraps around the sides of the car would have advantages
(for example, the E-type Jaguar).
Crush depths (under test) of 80 to
90 mm for the adult headform appear appropriate.
5 Benefits and costs
The UK Department of Environment,
Transport and the Regions estimates that improved vehicle design, in accordance
with proposed EU requirements, should reduce pedestrian fatalities by 10%
after three years and 20% after 8 years [10].
The DETR estimate may be optimistic:
the UK Transport Research Laboratory (TRL) has estimated that 8% of all
pedestrian fatalities and 21% of all pedestrian serious injuries could
be prevented through improved vehicle design [2, 12].
McLean [3] points out that Australia
may have more to gain from pedestrian friendly vehicle designs because
urban traffic speeds are generally higher in Australia and a greater proportion
of pedestrian accidents are likely to take place at the impact speeds simulated
in the EEVC procedures.
As indicated above, there is wide
variation between the TRL and industry in the estimated costs of compliance
with the proposed requirements [16]. Looking at the longer term, when pedestrian
friendliness is taken in to consideration in the early stages of the design
process, then the TRL cost of compliance estimates are considered to be
reasonable.
Using conservative values for injury
reduction, TRL estimates that the benefit/cost ratio of potential improvements
would exceed 7 to 1 [2, 4, 12].
6 Implementation
Experience over the last two decade
suggests that introduction of road user protection initiatives is expedited
if they are incorporated in consumer test programs (see Table A2, Appendix
A). In some cases, the regulation test is less severe than corresponding
consumer test. Furthermore it takes time for penetration of new initiatives
into the Australian vehicle fleet. It will take ten years for at least
half of the fleet to comply with a new regulation and six years for at
least half of the annual kilometres travelled to be in vehicles which comply
with a new regulation.
7 Conclusions
Pedestrians struck by the front of
a vehicle account for 15% of all road fatalities in Australia.
Test procedures have been developed
in Europe to evaluate the pedestrian friendliness of vehicle fronts. The
people conducting these tests in Europe have concluded that relatively
simple changes to detail can lead to major improvements in pedestrian protection.
These changes can be cost-effectively introduced if they are taken into
account early in the design stage of a new model.
Consumer tests conducted by Euro-NCAP
reveal that there is room for a great deal of improvement with current
vehicle models. The situation is likely to be similar in Australia, where
ANCAP has recently commenced testing to the Euro-NCAP pedestrian protection
protocol.
References
1. Coxon, C. G. 1999, 'Safer
Cars for Pedestrians', Proceedings of Road Safety Conference, Perth,
November 1999.
2. Paine, M. P. 1999, Protecting
pedestrians by Vehicle Design, unofficial report on an international
seminar held in Adelaide in February 1999. Copy at: http://www1.tpgi.com.au/users/mpaine/ppvd.html
.
3. McLean J. 1996 Pedestrian
Friendly Vehicle Front Structures. A Review of the Research Literature,
CR166,
Federal Office of Road Safety, Canberra, July 1996.
4. Fisher, A.J. and Hall, R.R. 1972
'The Influence of Car Front Design on Pedestrian Accident Trauma'. Accident
Analysis and Prevention 4, pp47-58.
5. Chiam H. and Tomas J. 1980 Investigation
of the effects of bull bars on vehicle-pedestrian collision dynamics, Federal
Office of Road Safety CR 13, October 1980.
6. Reilly-Jones C. and Griffiths
M.J. 'The Effects of bull bars on pedestrian injury mechanisms and kinematics,
Proceedings
of the 15th International Technical Conference on the Enhanced
Safety of Vehicles, Melbourne, Australia.
7. Streeter L., Anderson R., McLean
J. and Garrett M. 1998 'Pedestrian Head Impact Testing at the University
of Adelaide', Proceedings of the 16th International Technical
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8. Anderson R. and McLean J. 1998
'Crashworthiness Research at the Road Accident Research Unit', Proceedings
of the Developments in Safer Motor Vehicles Seminar, Staysafe, March
1998.
9. Yoshida S. 1998 'Computer Simulation
System for Car-Pedestrian Accident', Proceedings of the 16th
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Melbourne,
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L. and McLean J.2000, 'Pedestrian Sub-system Testing in Australia', Proceedings
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Sydney, March 2000.
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Proceedings
of the 16th International Technical Conference on the Enhanced
Safety of Vehicles, Windsor, Canada.
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S. 1996 'The Validity of the Proposed European Pedestrian Protection Procedure
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Author Biographies
Michael
Paine is a mechanical engineer with over twenty five years experience
in the fields of automotive safety and vehicle construction standards.
In 1990 he started an engineering consultancy and has worked on a range
of vehicle-safety related projects including: consumer crash tests, child
restraints, visual ergonomics, bus safety, vehicle inspections and assessment
of vehicle defects.
Chris Coxon is a mechanical
engineer who has worked in the aircraft industry in America and automotive
industries in Australia. He has worked in road safety for 15 years and
has been involved in the Australian New Car Assessment Program (ANCAP)
since its first test in 1992. He has been chair of the ANCAP technical
committee since 1994. ANCAP publishes relevant vehicle occupant protection
information for buyers of new cars using the best biomechanical research
and test protocols from international sources.
The views expressed
in this paper are those of the authors and do not necessarily represent
the views or policy of any organisation.
Appendix A