Safety Ratings Decoded: What NHTSA and IIHS Scores Mean for Sedan Shoppers

Two Organizations, Two Different Methodologies

When sedan shoppers encounter safety ratings, they typically see two distinct sources: NHTSA (the National Highway Traffic Safety Administration, a U.S. federal agency) and IIHS (the Insurance Institute for Highway Safety, an independent nonprofit funded by auto insurers). Understanding that these are separate programs with different goals is the essential starting point.

NHTSA's New Car Assessment Program uses a five-star scale and focuses on measuring injury probability across frontal, side, and rollover tests. The resulting star ratings reflect how likely an occupant is to sustain a serious injury in each scenario — five stars signals less than a 10% probability in that category.

IIHS, by contrast, uses a descriptive four-level scale — Good, Acceptable, Marginal, Poor — and evaluates structural performance, injury measures recorded by crash dummies, and increasingly, the quality of active safety technology. IIHS introduced the challenging small overlap front test in 2012 and has continuously updated its side-impact protocol to account for the growing prevalence of taller vehicles like SUVs and trucks on U.S. roads.

Because the two systems test different crash scenarios at different speeds and measure outcomes differently, a high rating from one organization does not predict performance in the other's tests. Reviewing both is essential for a complete picture.

What NHTSA's Stars Actually Measure

NHTSA tests vehicles in three primary categories: frontal crash (driver and passenger), side crash (moving barrier and pole), and rollover resistance. Each earns its own star rating, and an overall vehicle score is derived from those components.

One important nuance: NHTSA's frontal test uses a full-width barrier, meaning the entire front of the vehicle contacts the barrier simultaneously. This differs significantly from real-world crashes, where partial-overlap impacts — where only a portion of the front structure absorbs the force — are common. That gap is precisely why IIHS developed its offset and small overlap tests.

When comparing sedans using NHTSA data, look beyond the headline overall rating. A vehicle might earn five stars overall but only three stars in the side pole impact test, which simulates hitting a tree or utility pole. That granularity matters for understanding real-world risk profiles.

Decoding IIHS Ratings and the Top Safety Pick Designations

IIHS evaluates sedans across a broader set of crash configurations than NHTSA, including the small overlap front test (where 25% of the vehicle's front strikes the barrier), the moderate overlap front test, side impact, roof strength, and head restraint and seat performance.

Beyond crash structure, IIHS also rates front crash prevention systems — the automatic emergency braking (AEB) technology that can slow or stop a vehicle before a collision — and, critically, headlight quality. Poor or inadequate headlights are associated with elevated nighttime crash risk, and IIHS has been vocal that many vehicles still earn only marginal or poor headlight ratings even in otherwise high-performing models.

The two IIHS award tiers work as follows:

• Top Safety Pick (TSP): Requires Good or Acceptable ratings on all six crash tests, plus at least Advanced or Superior front crash prevention, plus at least one Acceptable headlight option.
• Top Safety Pick+ (TSP+): The same crash test requirements, but demands Good or Acceptable front crash prevention and at least Good headlights on at least one available trim.

Because headlight quality often varies by trim level, a sedan might earn TSP+ with a specific lighting package but not with base-level headlights. Always verify which exact configuration earned the designation. See our full sedan buyer's framework for how safety ratings fit into a broader evaluation process.

Using Both Systems Together When Comparing Sedans

Experienced sedan shoppers use NHTSA and IIHS data as complementary inputs rather than substitutes. A vehicle that earns five NHTSA stars and IIHS TSP+ is demonstrably well-regarded across different testing regimes. But a vehicle with five NHTSA stars and a Marginal IIHS small overlap rating warrants closer scrutiny — the structural performance in offset crashes may be a genuine concern.

Sedan body style introduces some specific considerations. Compared to SUVs and trucks, sedans typically have lower hood lines and different structural geometries, which can affect how they perform in side impacts with taller vehicles. IIHS has updated its side-impact protocol specifically to simulate the real-world scenario of a sedan being struck by an SUV-height barrier — a meaningful change for anyone cross-shopping body styles. For that broader comparison, see our sedan vs. SUV analysis.

Also worth noting: driver-assistance features like lane-keeping assist, blind-spot monitoring, and rear cross-traffic alert are not directly tested or scored by either NHTSA or IIHS crash programs, though IIHS does evaluate AEB performance separately. A sedan's overall safety profile in day-to-day driving depends on these systems too, not just its structural integrity in standardized collisions.

For sedan shoppers who also want to understand how spec sheet numbers translate into real-world performance, our guide to reading sedan spec sheets provides useful context.