Benefits of a 64km/h offset crash test in Australia
Monash University Accident Research Centre Report #173 - 2000
Full report in .pdf format [760KB]
Authors: Brian Fildes, Kennerly Digges, Magda Les & Claes Tingvall
A previous study was undertaken to estimate the benefits of Australia adopting the EEVC proposed frontal offset standard which specifies a dynamic crash test with a 40deg overlap into a deformable barrier at 56km/h using Harm figures derived in 1995. Consumer groups routinely carry out offset crash tests of new passenger cars using the European offset test procedure, but at a higher 64km/h, crash test speed. These independent test are aimed at providing information to the general public on the safety performance of new vehicles to help consumers choose safer cars. This study set out to assess the benefit in reduced societal Harm if manufacturers met the regulation requirements at the higher 64km/h crash test speed. Using the same method as in the earlier study, a set of assumptions was developed to estimate likely injury reductions from compliance with the 64km/h test. These were then converted into likely annual Harm savings and Harm saved per vehicle. On the basis of the evidence presented here, the 64km/h crash test seems to provide considerable benefit to Australia in addition to that expected from ADR 73/00. The total benefit likely to accrue if all cars were to comply with the 64km/h crash test would be somewhere between A$404 million and A$520 million annually with 100% fleet compliance. The break-even cost per car across its lifetime would be on average somewhere between A$404 and A$651. The additional benefit above ADR 73/00 would be of the order of 24% to 36% in reduced Harm in frontal crashes. No data were available on any likely disbenefit resulting from designing for the higher crash test and further research is warranted to confirm this. These savings are conservative, based on more recent injury costs published by the Bureau of Transport Economics, Canberra, Australia.
An earlier report by the Monash University Accident Research Centre demonstrated that the introduction of a new dynamic offset frontal standard incorporating the recently introduced European standard was likely to provide significant Harm reductions to passenger car occupants in frontal crashes (Fildes, Digges, Dyte, Gantzer & Seyer, 1996). These benefits were calculated for two crash test speeds, namely 56km/h and 60km/h.
The Land Transport Division of the Commonwealth Department of Transport ultimately implemented a new Australian Design Rule ADR 73/00, which harmonised with the European test configuration and injury criteria at a 56km/h crash speed.
In recent years, the New Car Assessment Program in Australia (ANCAP) introduced a dynamic offset crash test in their program of assessing the relative performance of new makes and models of passenger cars sold in Australia. This crash test essentially adopts the same crash and injury criteria in ADR 73/00 but at an increased crash speed of 64km/h.
This study estimated the likely benefits to Australian consumers of a vehicle meeting this more stringent crash test requirement and whether there are likely to be any disbenefits in increased Harm to a vehicle from complying with this requirement.
European & Consumer Offset Tests
ADR 73/00 specifies a range of head, neck, chest, femur and lower leg criteria for two Hybrid III test dummies situated in the front seat of a passenger car impacting a deformable face fixed barrier offset 40% on the driver's side.
The injury criteria specified for the dummies are more comprehensive than those that currently apply in ADR 69 or FMVSS 208. In addition, there are also criteria specified for maximum steering wheel intrusion in an upward direction and in rotation. This is seen as a real benefit for improved occupant protection by providing a more comprehensive test of the likelihood of injury in a relatively severe and common collision.
ADR 73/00 calls for a crash test impact speed of 56km/h. Tests conducted by ANCAP, EuroNCAP, and those conducted by the Insurance Institute for Highway Safety (IIHS) raised this crash severity figure by around 15% to 64km/h. The rationale for this is based on the philosophy that consumer tests should be more stringent tests of crashworthiness than those required by regulation, and that the higher test speed more clearly discriminates occupant protection performance between the vehicles.
The previous study (Fildes et al, 1996) showed a likely Harm reduction of somewhere between A$297 and A$418 per annum if all passenger cars were to comply with the proposed European standard (a 17% to 23% reduction in Harm in frontal crashes). The final saving would depend upon the percent of frontal airbag sales at the time of implementation. There was an expectation that a higher crash test speed would lead to higher benefits (eg; the benefits in this report for 60 km/h were between 10% and 15% higher) with little or no apparent disbenefits.
Likely Injury Reductions
Some limited test and dummy (injury) data were available from consumer crash tests previously undertaken in Europe, the USA and Australia on which to base the likely injury reduction figures. These data were examined, along with previous estimates in Fildes et al (1996), to arrive at the expected savings. From this examination, nine assumptions were developed and fed into the Harm analysis. These assumptions are outlined in Table 1 below:
Table 1 The nine critical assumptions used in the 64km/h benefit analysis
|1||A universal benefit would accrue from a general crashworthiness design improvement (15% reduction for 69% of the frontal Harm).|
|2||There would be an added benefit from 100% fitment of a driver airbag, which would be accelerated by mandating the offset test.|
|3||There would be fewer chest injuries from more stringent criteria, mainly for small to medium sized car occupants.|
|4||Fewer pelvic and thigh injuries from more stringent femur load and time dependent injury criteria.|
|5||New knee criteria would lead to fewer knee injuries for all crashes up to the test speed.|
|6||Fewer tibia and fibula fractures from inclusion of Tibia Index.|
|7||Fewer ankle-foot injuries from structural improvement to the floor and toe-pan areas.|
|8||A reduction in neck injuries by including a neck injury criterion.|
|9||Equal effectiveness would apply to occupants in all front-seating positions.|
Test data collected by ANCAP and IIHS were addressed to test for any likely disbenefits. Evidence from the ANCAP program failed to demonstrate that Australian vehicles were particularly stiff, although it was noted that most of these vehicles pre-dated the introduction of this requirement and may not be representative of current models.
Furthermore, Adrian Lund and colleagues at the IIHS conducted a series of comparative crash tests looking at the relative effects of geometry, mass and vehicle structure (Lund 1999). Their results showed that increased mass and increased ride height of the striking vehicle increased both the deformation of the struck vehicle and the struck vehicle drivers injury risk. However, increased stiffness produced inconsistent results, increasing extent of struck vehicle deformation but not always increasing dummy injury measures. Even large changes in striking vehicle stiffness were apparently mitigated by minor changes in vehicle geometry. IIHS concluded that the geometric location of stiff elements in the fronts of vehicles, and how that affected the intrusion profile in the struck vehicle was more important than overall vehicle stiffness in side impact compatibility.
On the basis of this analysis, it was not possible to estimate any disbenefit from the higher test speed and, therefore, no disbenefits were included in the calculations. This does not mean that there are no disbenefits from the 64km/h frontal offset test, but rather no data exists currently to confirm the presence of these. More research is warranted here when it is possible to assess how vehicle designs might be influenced by this higher crash speed.
The Harm Reduction Method
An analysis was then performed using these assumptions as a basis for calculating the likely Harm saved by the 64km/h offset requirement. The Harm Reduction method developed by the Monash University Accident Research Centre in conjunction with Professor Kennerly Digges of the George Washington University in Virginia that had been used in the earlier offset benefit study was again used here.
The national Harm database developed previously (eg; Monash University Accident Research Centre, 1992; Fildes, Digges, Carr, Dyte & Vulcan 1995; Fildes et al, 1996) was the basis for calculating the benefits of the 64km/h requirement. Allowances were made for subsequent vehicle safety improvements such as ADR 69 in arriving at these benefits.
Analysis by body region was undertaken using a 3-step cascading model. Harm saved from the universal benefit was first deducted, followed by increase in airbag usage (up to 100%) and finally specific countermeasure benefits. Given that the 1996 and current rates of sales of passenger cars with driver airbags was not known, these benefits were calculated for a range of possible airbag sales rates from 70% to 100% for new passenger cars.
The benefits of the 64km/h crash test requirement were calculated for both the annual Harm saved assuming all vehicles in the fleet were compliant as well as the unit Harm benefits per car across its lifetime. In computing unit Harm benefits, 5% and 7% discount rates were employed for either a 15 or a 25-year fleet life.
Annual Harm Benefits
The annual Harm reduction amount that would accrue from the 64km/h offset requirement was estimated to be between A$297 million and A$520 million (in $1996 values). This represents an additional annual Harm saving of between 24% and 36% over that estimated at 56km/h. This equates to an annual Harm saving of A$305 million to A$534 million in 1999 dollar values. Naturally, the full benefits would only apply when all vehicles in the fleet comply with this requirement.
As noted earlier, this assumes no disbenefit would occur that would negate some of these savings. It is important to stress that while there was no evidence found to suggest that the higher test speed would influence design such to induce more injuries at other test speeds, this needs to be tested more rigorously when suitable data become available.
Unit Harm Benefits
The unit Harm benefit (the average savings per car across its lifetime) was calculated using 5% and 7% discount rate and 15 and 25 year fleet life. These estimates showed that unit Harm savings for the 64km/h requirement would be somewhere between $304 and $668 per car in A$1999 values.
It should be noted that the most conservative estimate was for a 20% reduction in frontal Harm attributed directly to this requirement, which assumes no benefit from increased frontal airbag use. Again, these figures are between 24% and 36% higher than that estimated previously for a 56km/h crash test speed.
This project was funded by the NRMA, RACV and RTA (NSW)