Trends in HIC, Chest G and injury risk, NHTSA crash tests, 1979-2010

The top chart shows average HIC for each model year of NHTSA crash testing between 1979 and 2010. The improvement is crystal clear, but there are some notes. The early years, specifically 1981-1984, showed a sharp drop in average HIC values for the tests as car companies strove to compete with each other on safety. 1985 saw a spike in HIC, especially for the driver; a large number of light trucks (pickups, SUVs, and vans) were tested this year, and their lower safety standards at the time skewed the results. The second major drop occurred from 1988-1994 for drivers, due chiefly to air bags. The introduction of passenger air bags did not result in a sudden drop in HICs, but gradual improvement continued. HIC improvement was gradual during the 1995-2004 period, followed by a near leveling out from 2005-2010. The leveling out of good results led to the replacement of this test.

At the very beginning of the test program, passenger HICs were slightly higher, on average; during the 1980s, driver HICs were often significantly higher, likely due to improved seat belt systems and better structures but the continuance of steering column problems. Air bags briefly gave driver HICs the advantage, but passenger air bags caused passenger HICs to become lower again during the 1995-2002 period. Less aggressive driver airbags gave driver HICs the advantage from 2003-2010.

Chest measures aren't quite as clear cut. The sharp 1981-1982 drop was likely due to improved structures and seat belts, but chest measures rose modestly, plateauing during the 1985-1999 period for drivers, despite the introduction of air bags. Passenger chest measures rose during the 1986-1996 period, despite the widespread introduction of air bags during this time period. A possible explanation is that early air bags were "firmer" and more aggressive than today's airbags, and seat belt pretensioners and load limiters came along in the late 1990s. Chest measures fell during the 2000-2004 period, but leveled out from 2005-2010.

Injury measures is another odd one. I took the average HIC and Chest G for each side for each model year, and translated that into the injury risk for the "average" vehicle. Your vehicle may vary.