See also Assessment of Pedestrian Protection Afforded by Vehicles in Australia - paper presented at Impact Biomechanics conference in Sydney on 16 March 2000.
Sponsored by: The Federal Office of Road Safety, Australian Department of Transport and Regional Services.
Convened by: The Road Accident Research Unit , University of Adelaide.
The 4th Expert Meeting of the International Harmonised Research Activities Pedestrian Safety Working Group will be held in Adelaide from the 22nd to the 24th of February, 1999. The Working Group is charged with developing an internationally harmonised and acceptable test procedure based on real world crashes to assess the safety performance of passenger vehicles in the event of a collision with a pedestrian. The Group is to recommend a test procedure to the 17th ESV meeting in 2001.
A two day public seminar will be held an February 25 and 26, 1999, following the meeting of the Working Group. The seminar will commence with presentations by members of the Working Group from the UK, USA, Japan and Australia on the pedestrian accident situation in those countries. The current state of knowledge on the impact biomechanics of the pedestrian/car collision will then be reviewed. This will be followed by a critical review of the pedestrian impact test procedures that have been developed in Europe and by the International Organisation for Standardisation and also in the United States. Particular attention will be paid to the proposed European Standard based on the European Experimental Vehicles Committee (EEVC) subsystem test procedures. A demonstration of the EEVC test procedures will be conducted at the Pedestrian Impact Test Facility developed by the Road Accident Research Unit of the University of Adelaide. The development of computer models of the collision will be described, together with the arguments for and against subsystem or full body collision reconstruction of pedestrian/car collisions. The seminar will conclude with presentations and a panel discussion on the IHRA work towards an internationally acceptable harmonised pedestrian impact test procedure.
The seminar will commence at the Stamford Grand Hotel, Glenelg at 10 am on Thursday, 25 February 1999. The seminar dinner will be held at the Hotel at 7.30 for 8 pm. The following day the seminar will resume with demonstrations of pedestrian impact testing at the RARU Pedestrian Impact Test Facility at 60 Everard Avenue, Keswick (bus transport will be provided from the Hotel at 9 am) followed by further technical sessions at the University of Adelaide. The seminar will conclude at the University of Adelaide by 4 pm.
The members of the IHRA Working Group who will be attending the seminar include:
TRL conservatively estimates that the benefit cost ratio is 7:1.
There is concern about the trend towards sport utility (four wheel drive) vehicles and the implications for pedestrian safety.
Euro-NCAP has been assessing pedestrian impact protection of popular vehicle models since the NCAP test program began in 1997 (?). The test procedures are described in more detail below. Last year (?) the energy of impact requirements of the Upper Legform Test were revised downwards substantially. Whereas under the initial test energy no current model vehicles apparently passed the test criteria under the revised test energy it is estimated that about one third of current vehicle models will pass the test.
The EU has just decided to proceed with a Directive requiring vehicles to meet minimum pedestrian protection requirements which (I understand) are the same as those applied by Euro-NCAP. The EU decided to proceed with this measure irrespective of the benefit cost calculations (which were the subject of considerable debate between industry and government).
The Japanese automotive consumer organisation OSA plans to introduce
Euro-NCAP style pedestrian impact tests. Australian NCAP is also likely
to introduce these tests into its assessment of new vehicles. The situation
is less clear in the USA but research is underway into test methods and
Given the inherent repeatability problems with a full dummy test European Experimental Vehicles Committee (EEVC) developed three sub-system tests: head, upper legs and knee/lower legs. 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 (for example changes to a bumper design to improve knee protection could result in increased head to bonnet impact velocity).
A headform in free-flight is "fired" at representative areas of the bonnet (US="hood") at a prescribed angle and speed. These prescribed values vary according to the geometry of the front of the vehicle - in particular the bumper "lead" and the height of the "bonnet leading edge" (the latter can be quite complicated to determine in the case of a smoothly contoured vehicle). Two headforms are used - in essence a child headform is fired at the front half of the bonnet and an adult headform is fired at the rear half of the bonnet. Six tests are conducted with each headform - at present the test organisation is at liberty to choose the locations with the intention that the "worst" locations are covered.
Decelerometers in the headform are used to determine HIC (spike was only about 8ms so is doesn't really matter whether it is reported as HIC15 or HIC36). Euro-NCAP assigns a red (poor) rating if the test results in a HIC of 1,500 or more.
The motor industry has expressed concern about the manner in which test locations are chosen. This is particularly important where repeat tests are conducted - for example, if the test is called up in a regulation then any conformance (audit) tests must be carried out in the same locations as the original compliance test. One alternative to consider is to prescribe, say, 50 geometric locations on the bonnet and for the 12 test locations to be chosen by random number selection. This might mean that a test did not cover the "worst" location on the bonnet and therefore an undesirable design might "slip through". However, the manufacturers would need to ensure that at least all 50 locations meet the requirement and this would be a great advantage to pedestrians. A random selection process might not be as appropriate for consumer testing, which assigns a score to the test results, rather than just pass/fail. On the other hand, the "expert" selection method currently used is also likely to be fallible.
A test device has been developed to simulate the adult human femur. The test therefore gives an indication of the likelihood of femur fracture. It consists of an instrumented aluminium tube with substantial padding on one side. It is fired at the leading edge of the bonnet at a prescribed angle and energy (or mass and speed), based on similar criteria to those of the headform test. The procedures have a minimum energy level at which a test is required and it is possible (but probably unlikely) that a vehicle can be designed so that it does not require the upper legform test (for example a BLE height under 650mm and bumper lead of 100mm).
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.
Now that the prescribed energy levels for the test have been reduced (see "Compliance and consumer testing") there do not appear to be any major objections to the test procedures and assessment criteria.
(Caution: this description might not be correct) A test device has been developed to simulate the human knee and main bones. An impact side-on to the plane of articulation of the knee is assumed. 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. 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 (which is the physical limit of the device).
The Japanese motor industry appears to be concerned about the bio-fidelity (accuracy of simulation of real human body parts) of the knee shear mechanism. NHTSA appears to be concerned that the test device contains frangible elements which need to be replaced after each test (on principle, they want a test device that can be calibrated after a test). Research is being carried out on an alternative device which uses friction plates but this seems, to me, to be vulnerable to repeatability problems - maybe the "principle" should be reviewed.
The three sub-system tests appear to be a suitable way to get started
at improving pedestrian safety through improved vehicle frontal design
- this initiative is long overdue. Ultimately full scale dummy tests will
probably be developed and these may supersede the sub-system tests. It
is evident however, that major advances can be achieved by immediately
implementing the EEVC procedures. It is important that all three tests
are adopted so that vehicle designs are not unintentionally "driven" in
a direction that could reduce protection in other areas.
An example of this was the talk given by Graham Lawrence on practical
tips for improving vehicle designs (everyone seemed to be frantically scribbling
notes during his talk):
For improved head protection he talked about the importance of 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. Crush depths (under test) of 80 to 90 mm for the adult headform appear appropriate. The traditional manner in which the bonnet joins the side of the car needs some lateral thinking - typically a vertical sheet metal section is attached to the gutter which supports the bonnet. This is very stiff under vertical impact loads and a cantilevered design with less vertical stiffness should be considered. Alternatively, a bonnet which wraps around the sides of the car would be good (i.e. the E-type Jaguar)
Upper leg protection
For improved upper leg protection he talked about 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.
The bumper needs localised compliance and then efficient energy absorption. Foam plastics are available to achieve this aim, together with recovery characteristics which 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.