Key Takeaways
Crash test safety ratings
Crash test safety ratings are scores assigned to vehicles after controlled laboratory collisions designed to simulate real-world accidents. Two main U.S. programs produce these scores: the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS). Each program uses different test scenarios, different measurement methods, and different scoring scales, so a high score from one program does not automatically mean a high score from the other. For families with children, knowing what each program measures, and what it does not, helps put those numbers in proper context.
NHTSA uses a 1-to-5-star scale derived from injury probability calculations on instrumented crash dummies. IIHS uses a categorical scale (Good, Acceptable, Marginal, Poor) based on structural performance and restraint system behavior.
Two programs, two different questions
NHTSA and IIHS both crash cars into barriers and measure what happens to occupants, but they are answering different questions. NHTSA asks: given a crash of a specific severity, what is the statistical probability that the driver or a front-seat passenger suffers a serious injury? IIHS asks: how well does the vehicle structure hold up, and how effectively do restraint systems manage occupant movement, across a range of crash geometries?
NHTSA expresses results as stars, one through five, per test category. The overall vehicle rating averages those categories. IIHS uses four performance tiers: Good, Acceptable, Marginal, and Poor. A vehicle can carry a five-star NHTSA frontal rating while earning only an Acceptable from IIHS on its small-overlap front test, because the two programs test different things at different speeds and with different barrier shapes.
Families reading window stickers or dealer websites will typically see the NHTSA overall star rating, because federal law requires it to be displayed. The IIHS rating does not appear on the sticker, so many buyers never look it up. Consulting both databases before a purchase gives a much fuller picture.
Ratings reflect controlled lab conditions
Both NHTSA and IIHS scores come from controlled laboratory crashes at specific speeds and angles. Real-world collisions vary enormously in speed, angle, and the objects involved. A high rating means the vehicle performed well in that specific scenario, not that it will perform identically in every real crash. No rating is a guarantee of outcome.
What the NHTSA tests actually measure
NHTSA's New Car Assessment Program runs three primary tests. The frontal test drives the vehicle into a full-width rigid barrier at 35 mph. The side-barrier test uses a moving deformable barrier to strike the driver's door at 38.5 mph. The pole test runs the vehicle sideways into a rigid pole at 20 mph to assess head protection from curtain airbags. A separate rollover resistance rating uses a dynamic handling maneuver rather than a physical rollover crash.
Injury risk is measured on instrumented dummies placed in the driver and front-passenger seats. NHTSA's standard rear-seat tests have historically used less severe scenarios than the front, which is worth noting for families whose children ride in the back. NHTSA has been updating its test protocols to address this gap, but the changes phase in over time, so older database entries may not reflect those revisions.
The star scale converts injury probability into a simple number: five stars means a less than 10 percent chance of serious injury in that specific test. That threshold sounds reassuring, but it applies only to that test configuration and speed, not to every crash a vehicle might encounter on the road.
35 mph
NHTSA frontal barrier test speed
NHTSA's New Car Assessment Program conducts its standard full-width frontal crash test at 35 mph against a rigid barrier.
40 mph
IIHS small-overlap front test speed
IIHS runs its small-overlap frontal test at 40 mph, with only 25 percent of the vehicle's front-driver side contacting a rigid barrier.
1 in 3
Estimated car seats used incorrectly
NHTSA has published estimates suggesting a substantial share of child safety seats on U.S. roads are not installed or used as intended by the manufacturer.
What the IIHS tests actually measure
IIHS introduced the small-overlap front test in 2012 because frontal crashes involving only the corner of the vehicle were causing serious injuries even in cars with strong overall NHTSA scores. In this test, 25 percent of the vehicle's front-driver side hits a rigid barrier at 40 mph. The test exposed structural weaknesses that a full-width barrier test does not load in the same way.
The side test uses a moving barrier representing a small SUV striking the vehicle at 31 mph, and a separate pole test runs the vehicle into a rigid pole at 32 mph at a 75-degree angle. IIHS also evaluates roof strength by pressing a metal plate against the roof to simulate rollover loads. Each test produces a separate rating, and IIHS awards Top Safety Pick or Top Safety Pick+ only when a vehicle meets a combination of thresholds across all tests and also earns a rating on its front-crash prevention system.
For rear-seat passengers, IIHS has been developing a rear-seat occupant protection evaluation. Results from that program are worth monitoring at iihs.org, because rear-seat protection directly affects children who ride there in forward-facing or booster seats. Pairing vehicle structure ratings with reliability score guidance helps families weigh long-term value alongside safety performance.
Child restraints, LATCH, and what ratings leave out
Neither NHTSA nor IIHS crash test ratings describe how easy it is to install a child safety seat in a specific vehicle, or whether the vehicle's LATCH (Lower Anchors and Tethers for Children) system is accessible and rated for the child seat being used. LATCH anchor weight limits vary by vehicle, and using the system beyond its rated weight limit can reduce protection rather than increase it.
Correct installation matters as much as the vehicle's structural rating. NHTSA provides installation guidance and maintains a list of certified child passenger safety technicians through safercar.gov. A technician can verify fit for a specific seat-and-vehicle combination at no cost through many fire stations and health departments.
Forward-facing, rear-facing, and booster seats each interact with vehicle geometry differently. A vehicle that scores well structurally may still have rear seat belt geometry that does not work well with a particular booster seat. Checking Consumer Reports' annual child seat installation ease evaluations, which test actual seat-vehicle combinations, fills a gap that crash test star ratings cannot address.
Look up the specific model year
Manufacturers sometimes change structural design mid-generation, so a rating for a 2021 model may not apply to a 2023 version of the same nameplate. Always search by the exact year you are considering in both the NHTSA (safercar.gov) and IIHS (iihs.org) databases. Checking fuel economy ratings for the same model year ensures all your vehicle data applies to the same vehicle.
This article is for general informational and educational purposes only. Always consult official government sources such as NHTSA and IIHS for current ratings, and verify child seat installation with a certified child passenger safety technician for decisions affecting your family's safety.