Australian New Car Assessment Program (ANCAP)
Guidelines for Crashworthiness Rating System
November 2000 - Subject to change without noticeThis is NOT an official ANCAP web site.
During 1999 ANCAP changed to Euro-NCAP test and assessment procedures. The following guidelines are still used for rating structure, restraint systems and head restraint design.
For IIHS rating guidelines see the PDF downloads at http://www.hwysafety.org/vehicle_ratings/ratings.htm
Web page created by Vehicle Design and Research Pty
Limited
email: mpaine@tpgi.com.au
CONTENTS
INTRODUCTIONBACKGROUND
RATING CATEGORIES
SAFETY FEATURES
STRUCTURE
- ASSESSMENT OF DEFORMATION
STEERING COLUMN
MEASUREMENTS OF DEFORMATION
INJURY MEASURES
- COMBINED INJURY RATING
OVERALL RISK OF LIFE-THREATENING INJURY
OVERALL EVALUATION
REFERENCES
SAMPLE FROM ANCAP BROCHURE
DASH AND DOORWAY DEFORMATION
These Guidelines have been published by the Technical Committee of the
Australian New Car Assessment Program (ANCAP) for the information of vehicle
manufacturers, regulators and consumer organisations. A knowledge of automotive
engineering is assumed. The details of rating system were originally developed
by Vehicle Design and Research Pty Limited (VDR) under contract to ANCAP.
ANCAP reserves the right to amend these Guidelines without notice.
Contact information
- Chris Coxon, Chairman, ANCAP Technical Committee
Office of Road Safety
Transport South Australia
33 Warwick Street
Walkerville South Australia 5081
Australia
For a less technical guide to the rating system see "How
the evaluations are performed" (NRMA web site)
Introduction
This document describes the rating system used in Australian New Car Assessment Program (ANCAP). The system has applied to ANCAP brochures from November 1996. and allocates a rating of GOOD, ACCEPTABLE, MARGINAL OR POOR for vehicle structural performance, occupant restraint/kinematics and key injury measurements. Appendix A contains a sample from a brochure.The document is intended to provide guidance for the preparation of NCAP brochures by persons with experience in crash investigation and crashworthiness evaluations. Due to its technical complexity it is not intended for general publication.
The philosophy behind the rating system is that the resulting brochure should present the typical car buyer with key information in a manner which is simple, useful and credible. The system should attempt to spread the ratings across the entire range from "good" to "poor". A rating of "good" should correspond to current best practice, not a theoretical ideal. Wherever possible, objective criteria should be used in arriving at ratings. Also it should be possible for different assessors (with suitable qualifications) to arrive at the same ratings.
Background
In 1978 the U.S. National Highway and Transport Safety Administration (NHTSA) began full frontal crash testing (56km/h) of popular vehicle models in the United States. The results were published for the information of consumers. This led to greater interest in the safety of vehicles.Since the mid 1970s at least one European car manufacturer has been conducting offset crash testing as part of its vehicle design program. In the late 1980s the German Automobile Club and the magazine Auto Motor und Sport began offset crash testing of popular European models (55km/h, 50% offset). The results are published in the magazine. In 1995 the US the Insurance Institute for Highway Safety (IIHS) began offset crash testing of U.S. models (64km/h, 40% offset).
In 1996 the Japanese National Organisation for Automotive Safety and
Victims' Aid (OSA) commenced publishing results for full frontal crash
tests in Japan (55km/h). In 1997 Euro-NCAP published the results of its
first series of crash tests (64km/h 40% offset, side impact and pedestrian
impact tests).
Rating systems for these crash tests have evolved in response to consumer
demands for a simple, non-technical presentation of the results. NHTSA
recently introduced the star rating system, based on the risk of the driver
or front passenger receiving a serious or life-threatening injury in a
full frontal crash at 56km/h. A shortcoming of this approach is that it
does not take into account structural performance or occupant restraint
performance. It is possible for a test to result in "good" head and chest
injury measurements (and therefore a good star rating) even though the
structure performs poorly. In these cases the risk to life in a slightly
different crash configuration, or slightly higher speed, could result in
a much higher risk of serious injury.
IIHS introduced a new style of rating system for its publication "Crashworthiness
evaluations - midsize 4-door cars". This provides a separate rating for
structure, occupant restraint and injury measures, together with an overall
rating. Ratings are also given for head restraint design and bumper performance.
An overview of the IIHS rating system is given in a paper issued at the
1996 ESV Conference (O'Neill et al 1996). This is the rating system now
used for Australian NCAP, but modified to include analysis of full frontal
crashes and front passenger performance. More information about occupant
restraint/kinematics is given in the paper by Estep & Lund (1996).
Rating Categories
Rating categories should be consistent for each evaluation. In accordance with IIHS practice, there are four categories for ratings.Good, Acceptable, Marginal and Poor
Injury measurements should be described in terms of protection from serious injury. For example a HIC of less than 750 indicates that there is "good" protection from serious head injury. (consumer research indicated that terms such as "high risk of head injury" were confusing).
Safety Features
This section of the brochure lists notable safety features which, in general, go beyond those normally fitted by manufacturers. Examples (in Australia) include air bags and ABS brakes.Possible design shortcomings could also be noted. An example is a hard protruding object which could be contacted by the head in a side impact or rollover crash.
Safety features are not rated..
Structure
The main item of interest is the loss of occupant survival space.The performance of the vehicle structure over the entire crash event is evaluated. The integrity of the occupant space is assessed through analysis of measurements of deformation, technical reports, photographs and high-speed film. Key areas of interest are movement of the dash and steering column, reduction in the width of the doorway opening, deformation of the firewall, footwell and floorpan, movement of pedals, integrity of the doors, ease of opening doors after the crash, the deformation of the roof and pillars and integrity of the seats. In assessing deformation, consideration should be given to how it affects the remaining survival space. For example, a large deformation might be acceptable if the initial clearance between a hazardous surface and the occupant is large and, at the height of the crash, there is no significantly increased risk of the occupant contacting that surface. In practice, popular vehicle models rarely have the luxury of such large initial clearances.
Assessment of deformation
It is evident from analysis of high speed film that many vehicles experience substantial elastic deformation at the height of the crash (noticeable in the above animation). Components such as the dash then spring back so that the residual (plastic) deformation is much less than the peak. No measurement of the elastic deformation of these components is taken during the crash (in any case, such measurements are likely to be difficult to achieve with on-board equipment). In the circumstances, elastic deformation should not be used as a factor in the rating of structure but it can help to explain some events, such as unusual head or knee contacts. An increase in the rate of deformation can also indicate that catastrophic failure is occurring and the structure is no longer absorbing significant amounts of energy.Steering column
The steering column usually collapses when struck by the occupant (including when an air bag is deployed). Therefore residual movement of the steering column is not an appropriate factor is assessment of the loss of survival space. However, the direction in which the steering column moves can affect air bag performance. For example, in several offset tests (Australian and IIHS) the steering column moved substantially towards the centre of the vehicle. The driver therefore hit the air bag on its outboard side and this resulted in undesirable occupant kinematics. In one case the driver's head rotated through 180 degrees so that the back of the head hit the A-pillar.The motion of the steering column can also increase the severity of head or chest impacts. In some cases the steering column was observed to have a substantial upwards motion at the moment when it was struck by the driver's head. The head was swinging downwards by this time and the resulting impact was more severe.
Measurements of deformation
The following guidelines are based on residual (plastic) deformation. An analysis of numerous offset crash tests conducted by IIHS and Australian NCAP suggests that dash movement and the reduction in driver's doorway width are the best indicators of loss of survival space. The ratings for these measurements are:| Rating | Measured change |
| Poor | 200mm or more |
| Marginal | 150-199mm |
| Acceptable | 80-149mm |
| Good | less than 80mm |
The worst of these two measurements should be used for an initial rating of structure. This initial structural rating can be modified by several other structural factors
|
Initial Rating
|
Good | Acceptable | Marginal |
| Item |
|
||
| Substantial footwell intrusion (350mm or more) | Marginal | Poor | Poor |
| Moderate footwell intrusion (250 to 349mm) | Acceptable | Acceptable | Marginal |
| Foot trapped by pedals or deformed panels | Marginal | Poor | Poor |
| Tools required to open door | Acceptable | Marginal | Poor |
| Doors open during crash | see "Occupant restraint" | ||
| Pedal moves to within 100m of seat structure | Acceptable | Marginal | Poor |
| Seat is detached (one or both sides of seat) | see "Occupant restraint" | ||
| Bonnet intrudes into survival space | Marginal | Poor | Poor |
| Fuel system leak - major (stream) * | Acceptable | Marginal | Poor |
*revised wording
Occupant Restraint
The performance of the restraint system (seat belts, seats, air bag & head restraint), over the entire crash event is evaluated. The motion of the occupants is assessed through analysis of measurements (e.g. seat belt reel out), technical reports, photographs and high-speed film. Key areas of interest are head, chest and knee strikes; air bag deployment and occupant kinematics, including rebound and partial ejection.The table below sets out guidelines for assessment of occupant restraint and kinematics. The factors resulting in a "poor" rating are generally due to equipment failure or equipment not performing as intended.
The worst of all four restraint ratings is used for the overall occupant restraint rating for a vehicle. However, greater weight is given to the driver restraint, in recognition of the lower occupancy rate for the front passenger position. This is done by elevating the worst passenger result by one level, for the purpose of determining overall restraint rating. For example, if the results for a vehicle are:
driver/full frontal: acceptable
driver/offset: good
passenger/full frontal: marginal
passenger/offset: good
then the "marginal" passenger rating is elevated to "acceptable" and
the overall rating for occupant restraint is "acceptable".
Note that peak and 3ms clip decelerations are recorded for head impacts.
These give an indication of the severity of the impact and the characteristics
of the surface.
| Rating | Criteria |
| Poor | A door opens during the crash |
| Poor | A seat becomes fully or partially detached, slides forward on one or both sides (of the seat) or the seat back fails - this also applies to unoccupied seats. |
| Poor | An occupant slides off one side of an air bag and makes a hard contact (70g or more) (also applies where an air bag clearly bottoms out or fails to inflate) |
| Poor | Seat belt failure (webbing, buckle, anchorages, retractor) |
| Poor | An occupant's head is partially ejected (more than 25% outside vehicle). (Note that this factor does not apply if the partial ejection is through a side window and that window is normally fitted with impact resistant glazing) |
| Poor | Severe motion of steering column increases risk of injury* |
| Marginal | An occupant slides off one side of an air bag but does not make a hard contact (<70g) |
| Marginal | An occupied seat tilts or twists substantially (without failure or sliding) |
| Marginal | An air bag appears to deploy properly but a high deceleration is experienced (70g or more) and HIC > 750 |
| Marginal | The driver's head or chest strikes the steering wheel, resulting in hard contact (70g or more) |
| Marginal | The passenger travels forward sufficiently to strike the dash and make hard contact (70g or more) |
| Marginal | The passenger travels forward sufficiently to strike its knees |
| Acceptable | In the absence of an air bag, no head or chest strike occurs but a high deceleration is experienced (70g or more) (e.g a whipping effect and/or stiff restraint system) |
| Acceptable | An air bag high deploys and a high head deceleration is experienced (70g or more) but HIC is 750 or less |
| Acceptable | The driver's head or chest strikes the steering wheel but decelerations are low to moderate (<70g) |
| Acceptable | During rebound, the occupant misses the seat back or head restraint |
| Acceptable | During rebound, the occupant's head strikes a window frame, B-pillar or roof. |
| Good | No head/chest strikes (other than air bag), decelerations low to moderate (<70g) and rebound is well controlled, with little tranverse or vertical movement of the occupant. |
Injury measures
| Measurement | Good | Acceptable | Marginal | Poor |
| HIC | <750 | 750-899 | 900-999 | 1000 or more |
| Chest Compression | <50mm | 50-59mm | 60-74mm | 75mm or more |
| Chest Acceleration# | <60g | 60-74g | 75-89g | 90g or more |
| Femur Axial Force* | <7.3kN | 7.3-9.0kN | 9.1-10.8kN | 10.9kN or more |
| Lower Leg Index | <0.8 | 0.8-0.9 | 1.0-1.1 | 1.2 or more |
Notes:
# Worst of chest compression and chest deceleration used as chest
rating
* IIHS set lower femur force limits for longer duration readings
These criteria vary from those used in previous ANCAP brochures. In
particular, the "high" (now "poor") HIC reading was 1250, compared with
1000 for IIHS (and FMVSS 208) so that the new criteria result the
overall injury rating for eight previously-tested Australian vehicles going
from "marginal" to "poor". Also the inclusion of chest acceleration criteria
results in the chest injury rating changing from "good" to "acceptable"
for some vehicles. IIHS criteria for leg injury are generally more lenient
than previous Australian ratings.
A broken dummy leg, foot or ankle is cause for a "poor" leg rating.
Overall rating for each body region
The worst of all injury measures is used in the overall injury rating for each body region. However, greater weight is given to the driver injury results, in recognition of the lower occupancy rate for the front passenger position. This is done by elevating the worst passenger result by one level, for the purpose of determining overall injury rating for a body region. For example, if the ratings for the head are:- driver/full frontal: acceptable
driver/offset: good
passenger/full frontal: poor passenger/offset: good
Combined injury rating
For the purpose of determining an overall crashworthiness rating for the vehicle (see "Overall evaluation") a combined injury rating is derived from the worst of head and chest ratings. If all head and chest ratings are "good" and one or more leg ratings is "poor" then the combined injury rating is downgraded to "acceptable". Otherwise the leg rating does not have an influence on the combined injury rating (which is weighted towards life-threatening injuries). Note that leg injury rating might have an influence on the overall ranking of vehicles.The following table gives an example of the derivation of overall injury ratings. In summary: the passenger/full-frontal rating is elevated by one level (e.g. "poor" becomes "marginal", "good" is unchanged); an overall rating is assigned for each body region, based on the worst of the ratings for driver and the elevated passenger rating; a combined injury rating is derived from the worst of the overall head and chest ratings (in this case "marginal"). These ratings are not intended to be published.
| Driver | Driver | Passenger | ||
| Overall | Full-frontal | Offset | Full front | |
| Head | Marginal | Acceptable | Good | Poor |
| Chest | Good | Good | Good | Good |
| Upper legs | Marginal | Good | Marginal | Good |
| Lower legs | Poor | - | Poor | - |
Note that passenger offset injury ratings are not usually published because they are generally much better than the other ratings and this can cause confusion about overall ratings. In the case of legs, the worst of left and right readings is used.
Overall risk of life-threatening injury
A risk of life-threatening injury, expressed as a percentage, is included for each vehicle. This risk is derived from the head (HIC) and chest (acceleration) measurements in accordance with the technique described in the November 1994 Australian NCAP Technical Report (contact the NRMA for a copy). This technique combines the risk for full frontal and offset tests.A rating (good to poor) for this risk is not provided because this might get confused with the separate ratings for head and chest injuries.
Note that the term "life threatening injury" is based on an interpretation of the AIS Coding Manual which might not have been intended by the authors of that manual: the AIS injury severity codes are:
- 1-minor,
2-Moderate,
3-Serious,
4-Severe,
5-Critical,
6-Maximum.
Head restraint position
The rating is based on IIHS criteria and manikin measurements: "height" is vertical distance from top of head restraint to top of manikin's head. "backset" is the horizontal distance from the front of the head restraint to the back of the manikin's head. The vertical reading (V) is reduced by 5mm and the horizontal reading (H) is reduced by 10mm in order to allow for different seat back angles (this has the effect of improving the evaluation). For adjustable head restraints which lock in position* two sets of measurements are taken: one in the fully down, fully back position and the other in the optimum lockable position (usually fully up and fully forward). If the lowest position is in the same zone as the optimum position then the rating is based on this zone. Otherwise the zone for the optimum position is used but is downgraded one level (e.g. good becomes acceptable) because so few motorists adjust their head restraints correctly*"lock in position" means the position of adjustment has a release device, such as a button, and can withstand a 100N downward force (proposed new wording) .
The resulting zones are rated as follows:
| Zone for lockable optimum position | |||||
| Zone for lowest pos. | Fixed or not Lockable | 1 | 2 | 3 | 4 |
| 1 | Good | Good | - | - | - |
| 2 | Acceptable | Acceptable | Acceptable | - | - |
| 3 | Marginal | Acceptable | Marginal | Marginal | - |
| 4 | Poor | Acceptable | Marginal | Poor | Poor |
Overall evaluation
A provisional overall rating is based on the "average" of structure, occupant restraint systems and injury, according to the following guidelines:| Good | Acceptable | Marginal | Poor |
| GGG | AAA | MMM | PPP |
| GGA | GGM | GGP | APP |
| - | GAM | GAP | MPP |
| - | AAM | GMM | GPP |
| - | GAA | GMP | - |
| - | - | AAP | - |
| - | - | MMP | - |
| - | - | AMM | - |
| - | - | AMP | - |
In this table the order is not important: GGA means two "good" and one
"acceptable". However, the order might affect overall ranking of a vehicle,
where priority is given to structure, then injury and finally restraints.
Finally the ANCAP Technical Committee reviews all of the information
and compares each vehicle with the other vehicles in the same group to
determine whether the provisional overall rating is appropriate for each
vehicle. This review process is more likely to result in an upgrading
for borderline cases than any downgrading. However, it is possible that
a review might pick up an undesirable crashworthiness feature that was
not adequately covered by these guidelines and therefore deserves consideration
of a downrating.
This rating system for overall evaluation was used for the November
1996 ANCAP brochure and subsequent ANCAP brochures.
References
Australian NCAP (1996) 'Buyers guide to crash tests: Small Car Update', November 1996.Estep C.R. & Lund A.K.(1996) 'Dummy kinematics in offset frontal crash tests', Proceedings of 15th International ESV Conference, Melbourne.
IIHS (1996) 'Midsize 4-door cars - Crashworthiness Evaluations', Insurance Institute for Highway Safety.
Hackney J.R., Kahane C.J & Chan R. (1996) 'Activities of the New Car Assessment Program in the United States', Proceedings of 15th International ESV Conference, Melbourne.
O'Neill B., Lund A.K., Zuby D.S. & Estep C.R. (1996) 'New vehicle crashworthiiness evaluations by the Insurance Institute for Highway Safety', Proceedings of 15th International ESV Conference, Melbourne.
World Wide Web sites concerning NCAP:
FIA (Euro-NCAP) http://www.fia.com/tourisme/safety/safint.htmIIHS http://www.hwysafety.org/
NHTSA http://www.nhtsa.dot.gov/cars/testing/ncap/stars.html
NRMA http://www.nrma.com.au/crashtests
OSA http://www.osa.go.jp/esiken2.html
VDR http://www4.tpg.com.au/users/mpaine/roadsafe.html
SAMPLE FROM ANCAP BROCHURE (December 1997)
Dash and doorway deformation
