In 1994 more pedestrians died on Australian roads than did motorcyclists and pedal cyclists combined [did passengers in vehicles]. Attempts to reduce the number of pedestrian casualties have concentrated on preventing the collision from occurring. This is because it has been assumed, incorrectly, that little could be done to reduce the severity of the injuries sustained by a pedestrian when struck by a car.
Pedestrian Injuries and Vehicle Design
Certain characteristics of vehicle design can have a marked effect on the nature and severity of the injuries sustained by a pedestrian struck by a vehicle. This report reviews the evolution of our understanding of that relationship. The development of vehicle test procedures to optimise the level of protection afforded to the pedestrian in the event of a collision is discussed, with particular reference to the relevance of these test procedures to the Australian situation.
Contrary to popular belief, pedestrians are run under by a striking car, rather than run over. This means that the shape and energy-absorbing properties of the bumper and the upper surface of the front of the car are the direct cause of injury to the legs and head of the pedestrian. In general, injuries resulting from being thrown to the road after being struck by a car are not as severe as the injuries due to the impact with the car itself.
Development of Pedestrian Impact Test Procedures
The development of pedestrian impact test procedures has involved the investigation of actual collisions between pedestrians and vehicles to identify those aspects of vehicle design which are related to the injuries sustained by the pedestrian. This work has proceeded in parallel with research into the tolerance of the human body to impact.
The two main groups which have been working on the development of test procedures are the European Experimental Vehicle Committee (EEVC) and the International Standards Organisation (ISO). Because of intractable difficulties in ensuring repeatability in a full scale collisions between a pedestrian crash test dummy and a vehicle, and also concern about the biofidelity of a pedestrian dummy, each group has approached the task by developing component, or sub-system, tests rather than a whole system test. For example, there is a test of the likelihood of a car bumper injuring the knee joint of a pedestrian whose leg is hit from the side at 40 km/h.
Application of Pedestrian Impact Test Procedures
The availability of pedestrian impact test procedures has made it practicable to introduce vehicle safety standards for pedestrian protection. The final report of EEVC Working Group 10 contains a draft EC Directive, or Standard, which, if approved, will require that all new models of cars sold in the European Union Countries after October, 1998 will have to pass the sub-system tests and all cars entering service will be required to comply by October, 2001.
The EEVC sub-system test procedures for pedestrian protection are also being used in the New Car Assessment Program (NCAP) crash tests being conducted by the Transport Research Laboratory for the United Kingdom Department of Transport. The first set of these tests has been carried out and the results are expected to be made public in 1996.
Cost-Benefit Analyses
Cost-benefit analyses of the probable consequences of the introduction of the draft EC Directive have been carried out by the Transport Research Laboratory (TRL) in the UK. These analyses indicate that the cost-benefit ratio is likely to be about 1:7.5 based on production costs and 1:4.3 based on the after tax cost to the consumer. Research in Germany, at BASt, on the likely benefits of the introduction of the draft Directive yielded data which was consistent with the TRL findings.
The European Automobile Manufacturers Association conducted a cost-benefit analysis which concluded that the cost-benefit ratio would be 57:1. However, the estimated cost of compliance with the draft EC Directive was about 20 times greater than the cost arrived at by TRL and BASt and the benefits were restricted to a reduction in pedestrian fatalities alone, excluding the benefits from a reduction in injury severity.
Pedestrian Protection and Vehicle Design in Australia
The value of the draft EC Directive in Australia, were it to be adopted as an Australia Design Rule for Motor Vehicle Safety, would be influenced by two additional factors. The first is that the proportion of pedestrians hit by a car, rather than by some other motor vehicle, is higher in Australia than in Europe, which would tend to increase the resulting benefits. The second is that Australia has one of the highest urban area speed limits in the world (60 km/h). The draft EC Directive specifies that the component tests be conducted at a speed of 40 km/h. It is probable that there would still be some benefit at higher impact speeds from requiring compliance with the EC Directive at 40 km/h but the effect of the difference in speed distributions is a matter which has yet to be established.
Establishment of a Pedestrian Impact Test Facility
There are several reasons to support the establishment of a pedestrian impact test facility in Australia. At present, the obvious choice would be a facility which could be used to test for compliance with the draft EC Directive and to investigate the potential benefits of such compliance at impact speeds higher than 40 km/h. Such a facility could also be used to assess the probable effect of a bull bar attached to a car on the risk of injury to a pedestrian struck by that vehicle. In addition to these applications, there would also be considerable value in the availability of a pedestrian impact test facility for research purposes.
A significant limiting factor in the development of more effective test procedures for both pedestrian protection and the protection of vehicle occupants in a crash is the present inadequate level of understanding of human tolerance to impact. The aim of the head injury research program of the NHMRC Road Accident Research Unit (RARU) at the University of Adelaide is to develop a more soundly based criterion for the tolerance of the human brain to impact to the head than is currently provided by the Head Injury Criterion (HIC). This is being attempted by relating the characteristics of the impact to the head to characteristics of the resulting injury to the brain in fatal pedestrian-car collisions. Because it is the only research program of its type in any country, RARU has been approached by three overseas research groups, in France, Japan and the USA, to collaborate in the validation, or otherwise, of mathematical models of brain injury. The value of these collaborative activities would be greatly enhanced if accurately measured information on head accelerations can be obtained from headform impact tests on cars similar to those involved in the cases investigated by RARU.
Conclusions and Recommendations
- The level of pedestrian protection provided by current passenger cars can be significantly improved with practicable design changes.
- The draft EC directive based on the EEVC test procedures is the best available means of assessing the level of pedestrian protection of a vehicle.
- It is likely that the benefits in terms of a reduction in pedestrian deaths, injuries and disabilities resulting from the adoption of the draft EC directive as an Australian Design Rule for Motor Vehicle Safety would be cost effective.
- Consideration should be given to the establishment of a pedestrian impact test facility in Australia to enable testing of vehicles and vehicle modifications to be conducted according to the EEVC test procedures.
- Consideration should be given to further research into the mechanisms of pedestrian injuries.
Type: Research and Analysis Report
Sub Type: Consultant Report
Author(s): AJ McLean
Topics: Pedestrian, Compatibility, Vehicle design
Publication Date: 01/07/96