Car mass and fatality risk: has the relationship changed?

Area of Science:

• Traffic Safety Research
• Automotive Engineering
• Public Health

Background:

• The relative safety disadvantage of small cars compared to large cars was less pronounced in post-1980s vehicles.
• This observation led to speculation that increasing fuel economy standards might result in fewer fatalities than initially anticipated.

Purpose of the Study:

• To investigate whether increasing fuel economy standards would indeed increase fatalities less than previously expected.
• To examine fatal crashes between two cars of similar model year to assess the impact of car mass on driver fatality risk.

Main Methods:

• Analysis of Fatal Accident Reporting System (FARS) data.
• Examination of driver fatality risk in relation to car mass for crashes involving vehicles of the same model year.

Main Results:

• The relative risk for driver fatality in a lighter car compared to a driver in a car 50% heavier was 3.7-5.1 for 1966-1979 cars.
• This risk decreased to 2.6 for 1984 cars.
• The risk increased to 4.1 for 1990 cars.

Conclusions:

• The reduced mass effect in mid-1980s cars was likely due to earlier adoption of crashworthiness improvements in smaller vehicles.
• As vehicle redesigns progress, the relationship between fatality risk and mass is expected to revert to pre-1980s patterns.
• Future increases in fuel economy may lead to greater increases in traffic fatalities than mid-1980s data suggested.