Using State Data to Assess Vehicle Performance

1. Using State Data to Assess Vehicle Performance Prepared by Rory Austin Office of Vehicle Safety Planning and Analysis National Highway Traffic Safety Administration rory.austin@nhtsa.dot.gov Presented by John KindelbergerNational Center for Statistics and Analysis National Highway Traffic Safety Administration 30th International Traffic Records Forum Nashville, TN July 26, 2004

2. Presentation Overview • Why Assess Vehicle Performance? • Example 1: Vehicle Crash Protection for Children • Example 2: Vehicle Braking Performance • Conclusion

3. Why Assess NewVehicle Performance? • Compliance with Federal Regulations • New vehicles must meet Federal Motor Vehicle Safety Standards (FMVSS) • Consumer Information • New vehicles are assigned ratings under NHTSA’s New Car Assessment Program (NCAP)

4. Measuring Vehicle Performance • Compliance and NCAP • Laboratory tests • Described in the Code of Federal Regulations • However… Do Laboratory Results Correlate with “Real-World” Performance? • Want changes to FMVSS to have safety benefit • Want to provide consumers with “good” information

5. “Real-world” Performance • Frequently determined from crash data • NHTSA’s State Data System (SDS) useful • Large numbers of cases needed for • Particular vehicle make and model • Relatively new vehicles (recent model years) • Vehicle Identification Numbers needed for • Identifying particular vehicle characteristics such as four-wheel drive or anti-lock brake system

6. Example 1: Vehicle Crash Protection for Children • Do some vehicle models provide better occupant protection for properly restrained children than other vehicle models? • Focused on • Frontal crashes (front impact) • Vehicle that did not overturn • 15 vehicle models • Model years 2000 through 2003

7. Example 1: Vehicle Crash Protection for Children • Child occupants were • 0 to 3 years old • In rear seat • In child restraint • Known injury severity (including no injury) • Older children were not included due to coding issues with booster seats

8. Example 1: Methodology Vehicle Performance for Vehicle Model = Number of Injured Children in Relevant Crashes in Vehicle Model / All Children in Relevant Crashes in Vehicle Model Approach requires information on ALL children Not just injured children

9. Example 1: Data Sets Used • Used Florida and Maryland • Some states could not be used because • No VINs • No information on uninjured occupants • No initial impact point • Not current enough to capture “new” model years

10. Example 2: Braking Performance • Do some vehicles have better braking performance than other vehicles? • Important because better brakes may help avoid a crash • Rear-end crashes • If following (striking) vehicle had stopped sooner, crash might not have occurred

11. Example 2: Braking Performance • But raw counts of rear-end crashes per vehicle model may reflect exposure • More vehicles of a particular model on the road • Vehicle models differ in miles traveled • Vehicle models differ in environment • Region or urban vs. rural • How can we control for exposure?

12. Example 2: Methodology • Exposure to rear-end crashes can be captured by involvement • leading (struck) and following (striking) • Higher volume models and certain travel patterns contribute to higher involvement • Potential measure of braking performance • Vehicles of model striking in rear-end crash / Vehicles of model involved in rear-end crash

13. Example 2: Methodology • Braking performance still affected by driver • Can control through use of logistic regression • Predict whether a vehicle in rear-end crash was striking (brake performance) or struck (control) • Explanatory variables include vehicle model, age, gender, and alcohol/drug involvement • Explanation by vehicle model indicates differences in braking performance

14. Example 2: Data Sets Used • Used Florida, Maryland, Missouri, Pennsylvania, and Utah • Needed VINs to identify vehicles with standard Anti-Lock Brakes • Involved 20 vehicles of model years 1998 through 2003

15. Conclusions • Both projects relate to possible consumer information programs under consideration • Final decisions have not been made regarding either project but… • State data is greatly informing our decision-making process AND • Will help all of us improve vehicle safety