Comparing published safety ratings for used cars

To compare crash test ratings across a used car shortlist, look up each car's exact model year in both major US rating programs and only compare like with like. The two programs are the federal government's 5-Star Safety Ratings from NHTSA and the Insurance Institute for Highway Safety (IIHS) ratings. Check that the cars are the same size and weight class, were tested under the same version of the test, and have the same equipment as the listing you are looking at. A higher score only means more when those conditions match. A small sedan with top marks and a large SUV with top marks are not equally protective in a collision with each other.

The two US rating systems and what they measure

NHTSA, the National Highway Traffic Safety Administration, gives vehicles star ratings from one to five. Most tested vehicles show an overall rating plus separate ratings for frontal crash, side crash and rollover resistance. The rollover rating estimates how likely the vehicle is to tip over in a single-vehicle loss-of-control crash. It is not a crash test in the same sense as the other two.

IIHS is funded by insurers and runs its own crash tests. Results use a four-step scale: Good, Acceptable, Marginal and Poor. It also rates headlights, front crash prevention systems and how easy child seat anchors are to use. Each year IIHS gives the Top Safety Pick and Top Safety Pick+ awards to vehicles that meet that year's criteria.

The two programs use different tests, so they can rank the same cars differently. One vehicle may have five stars from NHTSA and a weaker IIHS result in a particular test, or the other way round. Using both gives a fuller picture than either alone.

Rules for a fair comparison

• Match the exact model year. Ratings belong to a specific model year. A redesign can change results a lot, so a rating for one year does not automatically carry over to the next.
• Compare within a size class. Crash tests measure how a vehicle protects its occupants under set test conditions, mostly against a barrier or a standardized moving object. Physics still favors heavier, larger vehicles when two vehicles collide. NHTSA itself advises comparing frontal ratings only among vehicles of similar weight.
• Check which version of a test was used. Both programs revise their tests over time. IIHS, for example, introduced a tougher side crash test with a heavier striking barrier, and many vehicles that had done well in the older version scored lower in the updated one. A Good rating under an older protocol is not the same as a Good rating under the newer one.
• Read award criteria by year. IIHS award requirements usually tighten over time. An award earned in one year shows the car met that year's bar, not today's.
• Confirm the equipment on the actual car. Headlight ratings often differ by trim because trims use different lamps. Front crash prevention ratings apply only if the car has that system. Some safety features were optional or limited to upper trims, so check the listing or window sticker details against the rated configuration.
• Check body style. A sedan and a hatchback version of the same model, or a two-door and four-door, may be rated separately or not at all.

Comparing Nissan models on a shortlist

Comparing Nissan models works the same way as any other brand. Ratings belong to a model and year, not to the brand. Suppose a shortlist includes a compact sedan, a midsize sedan and a compact SUV from Nissan. This is an illustrative example, not a ranking. Look up each model's year individually, then compare first within the same class: sedan against sedan, SUV against SUV. If you are weighing a Nissan against a rival, compare it with the competitor in the same size class and model year rather than with another Nissan in a different class.

Watch for generation changes. Several Nissan nameplates have been redesigned over the years, and a used car from the last year of an old generation can rate quite differently from the first year of the new one, even though the name is the same. When a listing's year sits near a redesign, confirm which generation it is before relying on a rating.

Comparing 2022 models

For 2022 vehicles, use the ratings published for the 2022 model year specifically. If a model carried over unchanged from earlier years, the programs may apply earlier test results to 2022, which is normal. In that case, check whether the result came from an older test version. A 2022 IIHS award reflects the 2022 criteria. Because the tests and requirements have changed since then, a 2022 vehicle and a newer one with the same award name were not necessarily judged on the same basis.

A simple worksheet for your shortlist

Recording the same fields for every car keeps the comparison consistent. Leave a cell marked "not rated" instead of filling a gap with a rating from a different year or configuration.

Field	What to record	Why it matters
Model, year, body style	Exactly as in the listing	Ratings are year- and body-specific
Size class	Small car, midsize car, small SUV, etc.	Fair comparisons stay within a class
NHTSA overall and per-test stars	Overall, frontal, side, rollover	Shows the federal results and rollover risk
IIHS crash test results	Each test, noting old or updated versions	Shows weak spots that an overall star rating can hide
IIHS award and year	Award name and the year it applied	Criteria change from year to year
Headlight rating for this trim	Rating matching the listing's headlights	Often varies by trim
Safety equipment present	Automatic emergency braking, blind-spot warning, etc.	Ratings for these systems apply only if the car has them
Open recalls	Result of a recall check by VIN	An unrepaired recall can affect safety regardless of rating

What the ratings cannot tell you about a specific used car

Published ratings describe how a new, correctly built example performed. They cannot account for the history of the individual car for sale. Poorly done structural repairs after a crash, airbags that were not replaced properly, or unrepaired recalls can all leave a particular car less protective than its rating suggests. Before buying, run the VIN through the federal recall lookup, review a vehicle history report for reported crashes, and have an independent inspection done if the car has had body or structural work. Tire condition and brakes also affect whether a crash happens at all, and the rating cannot reflect them.

Ratings from other regions, such as Euro NCAP or Australia's ANCAP, use different tests and scoring and often cover vehicles built to different specifications. For a US-market car, rely on the US programs, and do not substitute a foreign result for a missing US one.

Choosing between cars on your shortlist

If the cars are in the same size class and similar years, favor the one with consistently strong results across the individual tests, especially under the updated IIHS tests, over one with a high overall score and a weak result in a single test. Also favor the trim with better-rated headlights and working crash avoidance features.

If the cars differ in size, first decide what size you actually need. Within that class, then pick the best-rated option. A larger, heavier vehicle generally protects its occupants better in a collision with a smaller one. The trade-off is often higher fuel use and purchase cost, and a larger vehicle may be harder to maneuver.

If one car is a newer model year and the other is older with similar ratings, the newer one was more likely tested under stricter protocols and more likely to have modern driver assistance features. That usually makes its ratings more meaningful, as long as its history and condition check out.