Understanding NHTSA's 5-Star Safety Ratings

When shopping for a new vehicle, safety is one of the most important factors to consider. The National Highway Traffic Safety Administration (NHTSA) operates the New Car Assessment Program (NCAP), which crash-tests new vehicles and assigns them star ratings on a scale of one to five. These ratings give consumers a straightforward way to compare the crash protection offered by different vehicles. A higher star rating means a lower risk of serious injury in the event of a crash.

This guide explains how the crash tests are performed, what the star ratings mean, how to interpret the results, and how to use safety ratings effectively when choosing your next vehicle.

What Are NHTSA Safety Ratings?

NHTSA safety ratings are the result of a standardized testing program that has been in operation since 1978. The program was created to provide consumers with objective crash performance data so they could make informed purchasing decisions. The ratings are based on physical crash tests and a rollover resistance evaluation conducted on new vehicle models each year.

The ratings use a five-star scale, where five stars represents the highest level of safety performance and one star represents the lowest. NHTSA tests vehicles in three main categories: frontal crash, side crash, and rollover resistance. Each category receives its own star rating, and there is also an overall rating that combines the individual scores.

It is important to understand that star ratings are most meaningful when comparing vehicles of similar size and weight class. A five-star subcompact car and a five-star full-size SUV both performed well in their respective tests, but the laws of physics mean that larger, heavier vehicles generally offer more protection in real-world collisions involving vehicles of different sizes.

How Crash Tests Are Performed

NHTSA conducts three types of evaluations as part of its New Car Assessment Program. Each test simulates a different type of real-world collision scenario.

Frontal Crash Test

In the frontal crash test, the vehicle is driven into a fixed rigid barrier at 35 miles per hour. The vehicle hits the barrier head-on, engaging the full width of the front end. Two instrumented crash test dummies are placed in the vehicle: one in the driver's seat and one in the front passenger seat. The dummies are equipped with sensors that measure the forces exerted on the head, chest, and legs during the impact.

The data from these sensors is used to calculate the probability of serious injury to the driver and front passenger. Lower injury probability translates to a higher star rating. This test evaluates the effectiveness of the vehicle's front crumple zones, seat belts, and air bags in protecting occupants during a head-on collision.

Side Crash Test

The side crash test simulates a common intersection collision. A moving deformable barrier weighing approximately 3,015 pounds is driven into the driver's side of the test vehicle at 38.5 miles per hour. The barrier is shaped to represent the front end of a typical vehicle. Two crash test dummies are used: one in the driver's seat and one in the rear seat on the struck side.

The sensors in the dummies measure forces on the head, chest, abdomen, and pelvis. This test evaluates the strength of the vehicle's side structure, the effectiveness of side-impact air bags, and the protection offered by the door panels and pillars. Side crashes account for a significant percentage of serious and fatal injuries in real-world collisions.

In addition to the moving barrier test, NHTSA also performs a side pole test, which simulates a vehicle sliding sideways into a narrow fixed object such as a tree or utility pole. The vehicle is propelled sideways at 20 miles per hour into a rigid pole on the driver's side. This test is particularly demanding because the force is concentrated on a small area of the vehicle's side structure.

Rollover Resistance

Unlike the frontal and side crash tests, the rollover resistance rating is not based on a physical crash test. Instead, NHTSA uses a static measurement called the Static Stability Factor (SSF), which is calculated from the vehicle's track width (the distance between the left and right wheels) and the height of its center of gravity. Vehicles with a higher center of gravity relative to their track width, such as SUVs and pickup trucks, are more prone to rollover.

The SSF is combined with a dynamic maneuver test called the Fishhook test, which involves a series of sharp steering inputs to determine whether the vehicle's tires lift off the ground during an aggressive lane-change maneuver. The combined result is expressed as a rollover resistance rating on the same one-to-five-star scale.

What Each Star Rating Means

NHTSA's star ratings correspond to specific ranges of injury probability calculated from the crash test data:

• 5 Stars: The vehicle provides the highest level of crash protection. The estimated probability of serious injury is 10 percent or less in the frontal crash test and 5 percent or less in the side crash test. For rollover, a 5-star rating indicates a rollover risk of less than 10 percent in a single-vehicle crash.
• 4 Stars: The vehicle provides above-average crash protection. The estimated probability of serious injury is between 11 and 20 percent for frontal crashes and between 6 and 10 percent for side crashes.
• 3 Stars: The vehicle provides average crash protection that meets but does not significantly exceed federal safety standards. The injury probability is between 21 and 35 percent for frontal crashes and between 11 and 20 percent for side crashes.
• 2 Stars: The vehicle provides below-average crash protection. The injury probability is between 36 and 45 percent for frontal crashes and between 21 and 25 percent for side crashes.
• 1 Star: The vehicle provides the lowest level of crash protection among tested vehicles. The injury probability exceeds 45 percent for frontal crashes and 26 percent for side crashes.

The overall star rating is a combined score that takes into account the frontal crash, side crash, and rollover resistance results. It provides a single summary metric for quick comparison between vehicles.

How to Interpret the Scores

When reviewing NHTSA safety ratings, keep the following points in mind:

• Compare within the same class. Star ratings are most useful when comparing vehicles of similar size and type. A midsize sedan should be compared with other midsize sedans, and a compact SUV should be compared with other compact SUVs.
• Look at individual category ratings. The overall rating is a useful summary, but the individual frontal, side, and rollover ratings can reveal important differences. A vehicle might earn five stars overall but have a three-star rollover rating, which could be a concern if you frequently drive on roads with a higher rollover risk.
• Check for driver and passenger differences. In some tests, the driver and passenger receive different injury probability scores. A vehicle might provide excellent protection for the driver but only average protection for the front passenger, or vice versa.
• Remember that ratings apply to specific model years. Manufacturers regularly update their vehicles, and safety performance can change from one model year to the next. Always check the rating for the specific year you are considering. You can look up vehicles on our site by make, model, and year to see their safety data.

Limitations of Crash Test Ratings

While NHTSA's safety ratings are a valuable resource, they have limitations that consumers should understand:

• Not all crash scenarios are tested. Real-world crashes occur at a wide variety of speeds, angles, and impact points. The standardized tests represent common scenarios but cannot cover every possible crash configuration. For example, NHTSA's frontal crash test is a full-width test, while many real-world frontal collisions involve a partial overlap.
• Compatibility between vehicles is not measured. The tests evaluate how well a vehicle protects its own occupants, but they do not measure the risk a vehicle poses to the occupants of another vehicle in a multi-vehicle collision. A very heavy vehicle may score well in crash tests while being more dangerous to smaller vehicles it collides with.
• Advanced safety technologies are not fully captured. Features like automatic emergency braking, lane departure warning, and blind spot monitoring can prevent crashes entirely, but they are not reflected in the star ratings, which only measure crashworthiness. NHTSA does recommend certain advanced safety features, but they are evaluated separately from the star ratings.
• Test conditions are controlled. Crash tests are performed under standardized laboratory conditions. Real-world factors such as weather, road surface, vehicle load, occupant size, and seat belt usage can all affect crash outcomes.

Comparison with IIHS Ratings

In addition to NHTSA, the Insurance Institute for Highway Safety (IIHS) is another major organization that conducts crash tests in the United States. The two programs complement each other but differ in important ways:

• Different tests: IIHS performs tests that NHTSA does not, including a small overlap frontal crash test (where only 25 percent of the front end hits the barrier), a moderate overlap test, an updated side crash test with a heavier barrier, and a roof strength test. These additional tests can reveal weaknesses that NHTSA's tests may not expose.
• Different rating scales: While NHTSA uses a one-to-five-star system, IIHS uses a four-tier rating system: Good, Acceptable, Marginal, and Poor. IIHS also awards Top Safety Pick and Top Safety Pick+ designations to vehicles that perform well across all their evaluations.
• Different focus areas: IIHS evaluates headlight performance, child seat ease of use, and crash avoidance technology effectiveness in addition to crashworthiness. These are areas that NHTSA's star rating system does not cover in its star ratings.
• Funding: NHTSA is a federal government agency funded by taxpayers, while IIHS is funded by auto insurance companies. Both organizations operate independently and their test results sometimes differ for the same vehicle.

For the most comprehensive picture of a vehicle's safety, it is best to consult both NHTSA and IIHS ratings. A vehicle that scores well in both programs is likely to provide strong crash protection across a variety of scenarios.

How to Use Ratings When Buying a Car

Here is a practical approach to using safety ratings during your vehicle search:

1. Start with the overall rating. Narrow your choices to vehicles with four or five stars overall. This immediately filters out the lowest-performing options.
2. Compare individual categories. Among your shortlisted vehicles, compare the frontal, side, and rollover ratings. Pay particular attention to any category where a vehicle scores noticeably lower than its competitors.
3. Check both NHTSA and IIHS. Look up each vehicle on both NHTSA.gov and IIHS.org. A vehicle that performs well in both programs offers more comprehensive protection.
4. Consider the complete safety picture. Beyond crash test ratings, look at the vehicle's recall history, owner complaints, and available advanced safety features. Our database lets you view all of this information in one place for any vehicle make and model.
5. Don't overlook active safety features. Systems like automatic emergency braking, forward collision warning, and electronic stability control can prevent crashes from happening in the first place. Look for vehicles that offer these features as standard equipment.

Safety ratings are one of the most objective tools available to consumers. By understanding how the tests work and what the ratings mean, you can make a more informed decision and choose a vehicle that offers the best possible protection for you and your family. Explore our vehicle components guide to learn more about the individual systems that keep you safe on the road.