A car’s safety rating is one of the most important factors to consider when comparing different makes and models. Understanding how they work and which organizations you can trust can help ensure you invest in a car that meets your needs.
What determines a car’s safety rating?
A car’s safety rating is determined by a series of crash tests and its safety features. There are two organizations both automakers and consumers rely on to test and rate car safety: the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS). These set the standards for how cars are rated and analyze different criteria to paint a full picture of how well a car can keep its occupants safe.
NHTSA safety ratings
After a series of crash tests, the NHTSA bases its ratings on your likelihood of being injured — with a 5-star rating going to the safest vehicle possible. This typically means that the vehicle has scored “good” on multiple crash tests. NHTSA ratings are often included on car comparison websites to help you quickly discern which cars are safest.
IIHS safety ratings
The IIHS conducts more strenuous tests on vehicles, putting them through different scenarios to rate them as one of the following:
A car that has good crashworthiness — meaning it limits injury and protects the people inside — is typically given a “good” rating.
Why does a safety rating matter?
The safety rating on a car can be a critical component when it comes to saving your life. According to the IIHS, the driver of a vehicle rated as “good” is 70% less likely to die in a left-side collision than the driver in a vehicle rated as “poor.” When you’re selecting your next car, check its safety ratings from both the NHTSA and IIHS to ensure you’re making a solid decision based on more than just getting a good price at the dealership.
What does the crash test process involve?
It depends on which organization you get your car safety ratings from. The NHTSA and IIHS both conduct comprehensive testing, and knowing your car ranks well with both can give you some added peace of mind during your shopping experience.
NHTSA crash tests
The NHTSA bases its score on three to four tests depending on the build of the car:
Frontal crash tests
The NHTSA tests a head-on collision scenario by using dummies of an average-sized adult male driver and a small-sized female passenger, both wearing seat belts. The crash assumes both vehicles are similar in size and weight, and that the crash occurs at 35 mph. After the test, injuries to the head, neck, chest and leg are evaluated.
Side barrier tests
The NHTSA tests a side barrier collision by using dummies of an average-sized adult male driver and a small-sized female passenger, both wearing seat belts. The crash test is designed to compare multiple vehicles with each other, and the test is conducted by crashing a heavy barrier into a standing vehicle at 38.5 mph. After the test, injuries to the head, chest, abdomen and pelvis are evaluated.
Side pole tests
The NHTSA tests a pole collision by using a dummy of a small-sized female driver wearing a seat belt. The vehicle is pulled sideways at 20 mph into a pole, with the collision occurring on the driver’s side. After the test, injuries to the head, chest, lower spine, abdomen and pelvis are evaluated.
Rollover tests are conducted to determine how top-heavy an SUV is and how likely it is to flip during a sharp turn or similar maneuver. The NHTSA doesn’t state any injuries it evaluates after the test is conducted or if it places test dummies inside the vehicle during the flip.
IIHS crash tests
Because the IIHS doesn’t rely on government funding, it’s able to conduct more strenuous tests under more conditions. When giving a car a rating, it will conduct these seven tests to ensure a car is safe to drive:
Frontal crash tests
The IIHS conducts three separate frontal crash tests when evaluating a vehicle:
- Moderate overlap tests
- Driver-side small overlap tests
- Passenger-side small overlap tests
These look at the impacts on a vehicle going 40 mph by using a dummy of an average-sized male driver.
Side crash tests
The IIHS’s side crash tests are designed to supplement the NHTSA’s tests by accounting for a taller barrier, which represents larger vehicles like trucks and SUVs. The tests evaluate injuries to the head, neck, chest, abdomen, pelvis and leg. While it doesn’t outline the specific measures of its tests, it does state that side airbags are a critical component in preventing head and other injuries.
Roof strength tests
To help test the strength of car roofs, the IIHS conducts a test that measures an SUV’s weight-to-strength ratio. It states that a “good” rating requires an SUV roof to withstand a force at least four times its weight. Cars with a weight-to-strength ratio of 2.5 or lower are rated as “poor.”
Head restraint and seat tests
The IIHS states that a geometric head restraint is critical when it comes to preventing neck sprain and other neck injuries. While it is possible that older cars won’t receive a “good” rating, a 2010 government standard has made it so that manufacturers are required to follow specific guidelines in the construction of head restraints — meaning nearly every car model produced after 2010 receives a “good” rating. This is tested by using a dummy with a more realistic spine, which is then accelerated in the seat to simulate a rear-end accident.
Front crash prevention tests
To receive a “superior” rating, a vehicle must have an automatic brake system that can either avoid a crash or reduce a vehicle’s speed during testing. Automatic brakes are evaluated at 12 and 25 mph, and forward collision warning is also factored in to a car’s final score.
Headlights are measured to ensure a vehicle can be properly seen on the road and properly illuminate other cars and objects. The IIHS tests how far a headlight can be seen from a variety of angles and measures glare for oncoming vehicles. Cars are evaluated on how well their low beams and high beams perform compared to an ideal system, with low beams on straight roads being the most important measure.
The Lower Anchors and Tethers for Children (LATCH) system was created to anchor car seats and booster seats in a car. The IIHS evaluates LATCH systems based on ease of use, the accessibility of lower anchors, the force it takes to attach the child restraints, the location of the anchors, presence of labels and the maneuverability of the LATCH system. Cars receive a “good” rating when the LATCH positions meet all five criteria.
What car safety features are considered necessary?
The NHTSA states that standard safety equipment like airbags, seat belts and a tire pressure monitoring system are three factors you should take note of when inspecting a car. Driver assistance technology like forward collision warning, lane departure warning, rearview cameras and automatic emergency braking are also helpful in keeping cars safe — and many new cars come standard with one or more of these.
The IIHS doesn’t have any specific recommendations, but it does have information on these features as well as headlights, speeding and distracted driving on its website. Also, find details about your state’s seatbelt laws. Even if you aren’t legally required to wear your seat belt, they saved nearly 15,000 lives in 2017 according to the NHTSA.
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Understanding how a car’s safety is determined is critical when you’re shopping for your next vehicle. To learn which cars rate highest, you can read our safest family cars guide. And when you’re ready to buy, compare your car loan options to ensure you’re getting the best deal available to you.
Frequently asked questions
To get even more answers, check out these commonly asked questions.
Why doesn’t the NHTSA conduct any tests on rear-impact collisions?
Because front- and side-impact crashes are responsible for more deaths, the NHTSA uses these areas to ensure a vehicle is safe.
How do I check a car’s safety rating?
Visit the NHTSA or IIHS websites to search their databases. While neither organization tests every car on the market, they do cover a wide variety of popular vehicles.
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