Crash tests are the most objective safety data most car shoppers ever see. But they are widely misunderstood. A 5-star NHTSA rating and an IIHS "Top Safety Pick+" designation are produced by completely different organizations running completely different tests. A vehicle can earn the top NHTSA rating and still fail a key IIHS test. Understanding what each program measures — and what neither measures — makes you a much more informed buyer.
NHTSA's New Car Assessment Program (NCAP) is a U.S. government program run by the National Highway Traffic Safety Administration. NHTSA tests vehicles in three crash configurations: a full-frontal barrier impact at 35 mph, side barrier, and pole impacts, plus a rollover resistance assessment. Each configuration produces a 1–5 star rating. The overall star rating is not an average — it reflects the worst-performing individual test.
In the frontal crash test, NHTSA measures forces on the crash dummy's head (HIC15), chest (compression in mm), and neck (NIJ). These measurements are compared against federal injury thresholds set under FMVSS 208. A vehicle earns 5 stars if it keeps all measurements below the threshold with enough margin. Two 5-star vehicles can have very different measurements underneath — one leaving 40% of the head injury budget unused, another using 95% of it. The star rating doesn't show that gap; SafeScore does.
The Insurance Institute for Highway Safety (IIHS) is a private, non-profit organization funded by auto insurers. It runs tests that are different from — and in some ways more demanding than — NHTSA's:
IIHS uses ratings of Good, Acceptable, Marginal, or Poor — not stars. A vehicle needs Good or Acceptable ratings across all test categories, plus a basic or advanced headlight rating, to earn Top Safety Pick. The higher Top Safety Pick+ designation requires Good headlights and Good or Acceptable across all structural tests.
A vehicle designed to perform well in a full-width frontal barrier test — which loads the entire front structure evenly — may not perform as well when only the corner of the vehicle takes the impact. NHTSA's test and IIHS's small-overlap test expose different structural weaknesses. Engineers who optimize for the full-frontal barrier do not automatically get small-overlap performance for free. This is why the same vehicle can carry a 5-star NHTSA overall rating and a Marginal IIHS small-overlap rating. Both organizations are measuring real things; they are just measuring different real things.
SafeScore is built on NHTSA frontal crash test sensor measurements — specifically HIC15, chest compression, and NIJ — expressed as a 0–100 injury-margin score. It does not incorporate IIHS data. IIHS data is subject to usage terms that restrict commercial redistribution without permission, and SafeCarCompare builds exclusively on NHTSA public-domain data so every underlying measurement can be independently verified.
SafeScore adds resolution within the NHTSA star tier. It does not replace IIHS results, which cover different crash configurations and measure different things. For a complete safety picture, check NHTSA star ratings, SafeScore, and IIHS ratings for the vehicles you are comparing.
Independence: SafeCarCompare is independent and not affiliated with NHTSA, IIHS, or any automaker. SafeScore is calculated from NHTSA public-domain data and is not issued or endorsed by NHTSA.
SafeCarCompare shows injury margins from NHTSA crash-test data — beyond star ratings. Enter any two vehicles to see head, chest, and neck injury margins side by side.