Proposed vehicle impact speed – severe injury probability relationships for selected crash types

1. Proposed vehicle impact speed – severe injury probability relationships for selected crash types 2015 Australasian Road Safety Conference, Gold Coast 14-16 October

2. Authors Chris Jurewicz, ARRB Group Ltd Dr Amir Sobhani, ARRB Group Ltd Dr Jeremy Woolley, Centre for Automotive Safety Research, University of Adelaide Dr Jeff Dutschke, Centre for Automotive Safety Research, University of Adelaide Dr Bruce Corben, Corben Consulting

3. Safe System No person should be killed or seriously injured on Australia’s roads. National Roads Strategy 2011-2020 Australian Transport Council (2011) A safe road system increasingly free of death and serious injury. Safer Journeys, New Zealand’s Road Safety Strategy 2010-2020, Ministry of Transport (2010) Source: adapted from Ministry of Transport (2010), Australian Transport Council (2009) and Office of Road Safety (2009).

4. Safe System • 1. People make mistakes. • 2. Human physical frailty. • 3. A forgiving road transport system: • Impact forces in collisions must not exceed the limits of human tolerance. • Speeds must be managed to that effect. • Need to take into account these human tolerance limits in designing and maintaining roads, vehicles and speeds. • Based National Roads Strategy 2011-2020 • Australian Transport Council (2011) Source: adapted from Ministry of Transport (2010), Australian Transport Council (2009) and Office of Road Safety (2009).

5. What are these tolerances? Key reference: Wramborg (2005)

6. Many questions about Wramborg speeds • No references, none. • Not verified by other research, peds excepted. • Fatalities, not severe injuries – Safe System relevance? • Are these actually impact speeds? Or velocity vector? Or delta-v? Not clear, not stated. • Do they apply to probability per person, vehicle, or crash? • Is 10% fatality risk in an impact acceptable/meaningful? • More reliable evidence is needed for Safe System research.

7. New evidence • US studies to refine e-call trigger algorithms • Number of studies over the past 20 years • Latest based on >100,000 reconstructed crashes in the NASS/CDS database • Delta-v threshold for MAIS3+, i.e. serious and fatal injury

8. New evidence • Key reference: Bahouth et al. (2014)

9. New evidence • Many assumptions: • seat belts worn • airbags • no rollover event • road user age 16-55 years • applies to the front-seat occupants of the hit vehicle • US fleet….. plus more

10. Adaptation to impact speeds Relationship between delta-v and impact speeds, and angle Given known angle φ and assumption of equal masses,estimate impact speedsand relationship to Pr(MAIS3+)

11. Impact speeds vs. Pr(MAIS3+) Source: based on Bahouth et al. (2014), Davis (2001) * probability applies to the bullet vehicle occupants.

12. Critical impact speeds Approximate critical impact speeds for common crash types • * Bullet vehicle, as it is the one with more severe outcome.

13. Critical impact speeds Assumptions and sensitivity of P(MAIS3+) to angle of impact

14. Critical impact speeds • Roundabouts, critical impact speeds dependent on design 40 km/h 40 km/h 30° 70° 55 km/h 30 km/h

15. Critical impact speeds • Development of X-KEEM-X

16. Discussion and next steps • Broad estimates only, many assumptions and variables • Local validation. • Is 10% FSI risk a valid threshold? • Useful to recognise vehicle mass differences. • Further discussion and refinement of models and critical speeds. • Research funding to inform the next generation of road safety policies.

17. Thank you chris.jurewicz@arrb.com.au