How safe is safe enough?

Car being crash-tested

If you've shopped for a new car or truck, you may have noticed a box called "Government Safety Ratings" on the window sticker.

Each vehicle is given one to five stars based on how well it performs in a series of crash tests performed by the National Highway Traffic Safety Administration (NHTSA).

The obvious question is: "How many stars are enough?"

If safety is a primary consideration when buying a new car or truck, here are the answers.

Frontal Crash Test Rating: Five Stars

NHTSA crashes every new car and truck into a wall at 35 miles per hour.

You want a vehicle that is designed and equipped well enough to reduce the risk of serious injury in such an accident to 10% or less.

For frontal crashes:

Five Stars means there's 10% or less chance of serious injury.

Four Stars means there's an 11% to 20% chance of serious injury.

Side-Impact Crash Test Rating: Four Stars

In this test, the government measures the potential injuries from being struck at 38.5 m.p.h. by a 3,015-pound ram.

Five Stars means there's 5% or less chance of serious injury.

Four Stars means there's a 6% to 10% chance of serious injury.

So holding to our 10% rule, you can live with four stars.

Rollover Rating: Five Stars

These stars indicate how stable a vehicle will be in an accident, not how likely you are to be injured.

According to NHTSA, the most stable vehicles have a 10% chance of rolling over -- and that's what you want, because the odds of suffering a serious injury increase dramatically if your car starts tumbling.

Five Stars means a vehicle will roll over in 10% of all accidents.

Four Stars means it will roll over in 11% to 20% of accidents.

To put a finer point on rollover scores, the rating may include a bar graph with a diamond in it that provides a more precise rollover score between increments for comparison shopping.

What if safety isn't a primary concern? What if stunning styling or 0-to-60 performance is your priority?

How much can you compromise on safety before you're recklessly risking your life?

Trade a star or two off the side-impact or rollover rankings, but don't compromise on the Five Stars for frontal crashes.

More information about the ratings and scores for all the cars and trucks NHTSA has ever tested can be found at

While you're online, take a look at how safe the cars and trucks you're considering are, based on the safety ratings from the Insurance Institute for Highway Safety, which is the insurance industry's watchdog group.

The IIHS also crash-tests new vehicles and awards safety designations of Good, Acceptable, Marginal and Poor based on a vehicle's crashworthiness.

If safety is a key issue, only vehicles rated Good should be considered.

On the surface, the government and insurance institute tests appear to duplicate one another, but that's not the case.

"The tests are really complimentary because, by and large, they are measuring different crash scenarios," says Russ Rader, spokesman for the insurance institute.

For example, the NHTSA frontal test is a full-width event, crashing a vehicle head-on into a stationary barrier and spreading the force of impact across the entire width of the vehicle.

The insurance institute version also uses a stationary barrier, but the crash is offset, so only part of the front end absorbs all of the force.

In side-impact tests, NHTSA uses a battering ram barrier about the height of a passenger car bumper. The insurance institute places the battering ram at about the bumper height of a full-size pickup or SUV.

The insurance institute's rollover scores rate a vehicle's crashworthiness in a rollover as opposed to NHTSA, which rates rollover probability.