predicting the used car safety ratings ... ... predicting the used car safety ratings...

PREDICTING THE USED CAR SAFETY RATINGS CRASHWORTHINESS RATING FROM ANCAP SCORES

by

Stuart Newstead and Jim Scully

April 2012

Report No. 309

ii MONASH UNIVERSITY ACCIDENT RESEARCH CENTRE

Project Sponsored By

The Vehicle Safety Research Group

PREDICTING THE UCSR CRASHWORTHINESS RATINGS FROM ANCAP SCORES iii

MONASH UNIVERSITY ACCIDENT RESEARCH CENTRE REPORT DOCUMENTATION PAGE

Report No. Date ISBN ISSN Pages

309 April 2012 0 7326 23790 1835-4815 (online) 48 + Appendices Title and sub-title: PREDICTING THE USED CAR SAFETY RATINGS CRASHWORTHINESS RATING FROM ANCAP SCORES Author(s): Stuart Newstead & Jim Scully Sponsoring Organisation(s): - This project was funded as contract research by the following organisations: Centre for Road Safety - Transport for NSW, Royal Automobile Club of Victoria Ltd, NRMA Motoring and Services, VicRoads, Royal Automobile Club of Western Australia Ltd, Transport Accident Commission, New Zealand Transport Agency, the New Zealand Automobile Association, Queensland Department of Transport and Main Roads, Royal Automobile Club of Queensland, Royal Automobile Association of South Australia, Department of Transport, Planning and Infrastructure South Australia and by grants from the Australian Government Department of Transport and Infrastructure, and the Road Safety Council of Western Australia Abstract: The aim of this study was to investigate whether the correlation between vehicle secondary safety ratings developed from crash tests and those developed using real world crash data could be improved. Logistic regression was used to re-weight ANCAP test scores to improve their relationship with Used Car Safety Rating (UCSR) crashworthiness scores. TAC claims data were then used to investigate whether the re-weighted ANCAP scores reflected relationships that would be expected from existing knowledge of real world crashes and ANCAP crash tests. Sixty-nine vehicle models were included in the analysis.

Analysis showed that the correlation between ANCAP scores and the UCSR crashworthiness estimates could be improved greatly by weighting the component ANCAP measures differently to the current ANCAP summary measure. Two broadly different approaches were utilised to achieve this. The first re-weighted the current summary scores from the offset frontal and side impact test, the second re-weighted each of the individual body region scores from each test. The second method produced slightly higher correlations with the UCSR crashworthiness measures however the first method had better face validity when validated against real world crash and injury distributions. Consequently, a new ANCAP summary measure based on the first method would be preferred for adoption in practice. Including bonus points given for performance in the optional side impact pole test and the presence of seatbelt reminder systems improved the relationship with the UCSR crashworthiness measure in all instances. Including vehicle mass in the new ANCAP summary scores investigated resulted in the highest correlations with the UCSR crashworthiness measure. However including mass effects in an ANCAP summary measure is problematic from the perspectives of the objectives of ANCAP and would need to be considered carefully. At best, the new ANCAP summary measures proposed could explain between 55% and 65% of the variation in UCSR crashworthiness scores highlighting that the current ANCAP protocols still do not reflect all important real world crash configurations and injury outcomes to key body regions.

Key Words: Crash tests, ANCAP, Crashworthiness, Safety ratings, UCSR, Head injury, Vehicle mass Disclaimer: This Report is produced for the purposes of providing information concerning the safety of vehicles involved in crashes. It is based upon information provided to the Monash University Accident Research Centre by VicRoads, the Transport Accident Commission, the New South Wales Roads and Traffic Authority, NRMA Ltd, Queensland Transport, the Western Australian Department of Main Roads, South Australian Department of Transport, Energy and Infrastructure and Land Transport New Zealand. Any republication of the findings of the Report whether by way of summary or reproduction of the tables or otherwise is prohibited unless prior written consent is obtained from the Monash University Accident Research Centre and any conditions attached to that consent are satisfied.

Reproduction of this page is authorised. Monash University Accident Research Centre, Building 70, Clayton Campus, Victoria, 3800, Australia.

Telephone: +61 3 9905 4371, Fax: +61 3 9905 4363 www.monash.edu/miri/muarc

iv MONASH UNIVERSITY ACCIDENT RESEARCH CENTRE

PREDICTING THE UCSR CRASHWORTHINESS RATINGS FROM ANCAP SCORES v

Preface

Project Manager / Team Leader:

Dr Stuart Newstead

Research Team:

Jim Scully

vi MONASH UNIVERSITY ACCIDENT RESEARCH CENTRE

Contents

EXECUTIVE SUMMARY .....................................................................................................VIII 

1.  INTRODUCTION ............................................................................................................... 1  1.1  BACKGROUND ...................................................................................................................... 1  1.2  AIMS AND SCOPE ................................................................................................................. 2  1.3  A BRIEF INTRODUCTION TO ANCAP ............................................................................... 3 

2.  DATA ................................................................................................................................ 5 

3.  METHODOLOGY .............................................................................................................. 6  3.1  LOGISTIC REGRESSION ANALYSIS OF ANCAP CRASH TEST SCORES ..................... 6  3.2  LOGISTIC REGRESSION ANALYSIS OF ANCAP BODY REGION SCORES ................. 8  3.3  LOGISTIC REGRESSION ANALYSIS USING ANCAP CRASH TEST SCORES

DERIVED USING ALTERNATIVE OPERATIONS INVOLVING BODY REGION SCORES ................................................................................................................................... 8 

4.  RESULTS ........................................................................................................................ 10  4.1  LOGISTIC REGRESSION ANALYSIS OF ANCAP CRASH TEST SCORES ................... 11  4.2  LOGISTIC REGRESSION ANALYSIS OF ANCAP BODY REGION SCORES ............... 15  4.3  LOGISTIC REGRESSION ANALYSIS USING ANCAP CRASH TEST COMPONENT

SCORES DERIVED USING ALTERNATIVE METHODS OF COMBINING BODY REGION SCORES ................................................................................................................. 20  4.3.1  ANCAP crash test score equal to the minimum body region sub-score ....................... 20  4.3.2  ANCAP crash test score equal to product of body region sub-scores .......................... 24 

4.4  CHOOSING ONLY A SUB-SET OF BODY REGION SUB-SCORES USING STEPWISE SELECTION ....................................................................................................... 28 

4.5  SUMMARY OF LOGISTIC REGRESSION ANALYSES ................................................... 30  4.6  THE PLAUSIBILITY OF RELATIONSHIPS SUGGESTED BY LOGISTIC MODELS

THAT RESULTED IN SUPERIOR CORRELATION BETWEEN UCSR CRASHWORTHINESS ESTIMATES AND ANCAP TEST SCORES ................................ 30  4.6.1  Models based on current overall scores for the ANCAP frontal offset test and the

wide object side impact crash test ................................................................................ 31  4.6.2  Models based on ANCAP body region scores.............................................................. 34  4.6.3  Summary of Comparisons with Real World Crash Type and Serious Injury

Distributions ................................................................................................................. 36 

5.  DISCUSSION .................................................................................................................. 38  5.1  THE ROLE OF VEHICLE MASS ......................................................................................... 39  5.2  REPRESENTATIVENESS OF ANCAP CRASH TESTS ..................................................... 42  5.3  ANALYSIS OF INDIVIDUAL BODY REGION SCORES WITHIN EACH ANCAP

CRASH TEST ......................................................................................................................... 43  5.4  SELECTION AND USE OF AN ALTERNATIVE ANCAP SUMMARY MEASURE

FROM THOSE CONSIDERED ............................................................................................. 45  5.5  PRESENTATION OF THE NEW SUMMARY ANCAP SCORE ALONGSIDE USED

CAR SAFETY RATINGS ...................................................................................................... 45 

6.  CONCLUSION ................................................................................................................ 48 

REFERENCES ....................................................................................................................... 49 

APPENDIX A: SUMMARY OF ANCAP AND UCSR DATA .................................................. 50 

PREDICTING THE UCSR CRASHWORT