It was NHTSA who first did side impact crash testing in the United States, starting with 1997 model vehicles, and oh boy, was their methodology flawed at first. They measured something called the "Thoracic Trauma Index" which indicated the risk of chest injury in a side impact. Nothing else went into the rating. If the TTI was 57 or below, corresponding with a risk of severe chest injury lower than 5%, it got 5 stars. (57-72 was 4 (6-10% risk), 72-91 was 3 (11-20% risk), 92-98 was 2 (21-25% risk), and 99+ was 1 star (26% or more risk)
Head injury criterion and pelvic injury were measured, but didn't figure into the rating. If the HIC was over 1,000 or Pelvic G's above 130, the vehicle got an asterisk by its star rating indicating a high risk of head or pelvic injuries, but the star rating would be unaffected. Sometimes the asterisk would not be included, depending on the rating release. The 1998 Mercedes C230, for instance. The rear passenger experienced a TTI of 67, and a HIC of 2,089. 4 stars! The driver's TTI was 86, but the HIC was 348. Never mind that the impact would be survivable for the driver, but the rear passenger would probably suffer fatal head injury; the driver only got 3 stars. The driver and rear passenger of the 1998 Honda CR-V both got five stars, just squeaking into the top category with TTI's of 57 for both occupants. The driver really could walk away with a HIC of 161; the passenger's HIC of 1,140 would indicate a likelihood of serious brain injury. Top-tier protection indeed!
NHTSA has rectified this problem with their ratings of 2011 and newer vehicles. Protection to the whole body is now taken into account, not just the chest, for both the side barrier and the new side pole crash tests. With the 2011 updates, NHTSA's side crash test rating system went from leaving out important information to giving a comprehensive view of a vehicle's side crashworthiness.
IIHS, which uses an SUV-style barrier traveling at 31 mph, rates side crashworthiness piecemeal, giving each category a "Good", "Acceptable", "Marginal", or "Poor", and doesn't calculate an overall injury risk. Nevertheless, vehicles with a high risk of severe injuries to any body region are marked down heavily, to a "Poor", or a "Marginal" at best, by IIHS' demerit system, and structure and head protection are included as well.
Head injury criterion and pelvic injury were measured, but didn't figure into the rating. If the HIC was over 1,000 or Pelvic G's above 130, the vehicle got an asterisk by its star rating indicating a high risk of head or pelvic injuries, but the star rating would be unaffected. Sometimes the asterisk would not be included, depending on the rating release. The 1998 Mercedes C230, for instance. The rear passenger experienced a TTI of 67, and a HIC of 2,089. 4 stars! The driver's TTI was 86, but the HIC was 348. Never mind that the impact would be survivable for the driver, but the rear passenger would probably suffer fatal head injury; the driver only got 3 stars. The driver and rear passenger of the 1998 Honda CR-V both got five stars, just squeaking into the top category with TTI's of 57 for both occupants. The driver really could walk away with a HIC of 161; the passenger's HIC of 1,140 would indicate a likelihood of serious brain injury. Top-tier protection indeed!
NHTSA has rectified this problem with their ratings of 2011 and newer vehicles. Protection to the whole body is now taken into account, not just the chest, for both the side barrier and the new side pole crash tests. With the 2011 updates, NHTSA's side crash test rating system went from leaving out important information to giving a comprehensive view of a vehicle's side crashworthiness.
IIHS, which uses an SUV-style barrier traveling at 31 mph, rates side crashworthiness piecemeal, giving each category a "Good", "Acceptable", "Marginal", or "Poor", and doesn't calculate an overall injury risk. Nevertheless, vehicles with a high risk of severe injuries to any body region are marked down heavily, to a "Poor", or a "Marginal" at best, by IIHS' demerit system, and structure and head protection are included as well.
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